CARDIOVASCULAR BENEFITS AND POTENTIAL HAZARDS OF PHYSICAL EXERCISE
IN ELDERLY PEOPLE*
*Doctoral
dissertation presented on the 11stof December 2004 at the Agora
Center, Jyväskylä, Finland by permission of Faculty of Medicine
of the University of Kuopio.
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The Finnish Centre for Interdisciplinary Gerontology, Department of Health
Sciences, University of Jyväskylä, Jyväskylä, Finland;
LIKES-Research Center for Sport and Health Sciences, Jyväskylä, Finland;
Department of Physical and Rehabilitation Medicine, Central Finland Central
Hospital, Jyväskylä, Finland;
Kuopio Research Institute of Exercise Medicine, Department of Physiology,
Faculty of Medicine, University of Kuopio, Kuopio, Finland
Published
(Online) |
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01
April 2005 |
© Journal of Sports Science
and Medicine (2005) 4, Suppl.7, 1 - 51
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This
review is based on the following original publications, which will be referred
to in the text as Studies 1-4:
1.
Kallinen, M., Suominen, H., Vuolteenaho, O. and Alen, M. (1998) Effort
tolerance in elderly women with different physical activity backgrounds.
Medicine and Science in Sports and Exercise 30, 170-176.
2.
Kallinen, M., Kauppinen, M., Era, P. and Heikkinen, E. The predictive
value of exercise testing for survival among 75-year-old men and women.
Submitted for publication.
3.
Kallinen M, Sipilä S, Alen M, Suominen H. (2002) Improving cardiovascular
fitness by strength or endurance training in elderly women. A population-based
randomized controlled trial. Age and Ageing 31, 247-254.
4.Kallinen
M, Era P, Heikkinen E. (2000) Cardiac adverse effects and acute exercise
in elderly subjects. Aging 12, 287-294.
ABSTRACT |
Large
and consistent beneficial effects with few adverse effects have
been found in relation to physical exercise in selected samples
of elderly subjects. However, thus far, it has not been confirmed
to what extent the effects of physical exercise among elderly people
are beneficial or even harmful in population-based studies. Additionally,
the role of exercise testing among elderly people remains unclear.
Firstly, the effects of prolonged physical training on cardiovascular
fitness in 66-85-year-old women were examined in a cross-sectional
study. Secondly, the predictive value of exercise-test status and
results, including exercise capacity for survival, were studied
in 75-year-old men and women. Thirdly, the effects of an endurance
and strength training programme were examined in women aged 76 to
78 years in a population-based randomized controlled trial. Finally,
the cardiac-adverse effects of acute exercise in the form of a cycle
ergometer test were clarified in 75-year-old men and women. In the
maximal exercise tests the mean peak oxygen uptake was respectively
26.2 and 18.7 ml·kg-1·min-1 among the physically active and less
active control women. High cycling power (Watts per kg body weight)
in the completed ergometer test was associated with decreased risk
for death (multivariate HR 0.20; CI 0.08 - 0.50). The 18-week strength
training resulted in a 9.4% increase in peak oxygen uptake while
the endurance training improved peak oxygen uptake by 6.8%. A significant
increase in cycling power in W/kg was found in the strength and
endurance training groups compared to controls. Five cases of cardio-
or cerebrovascular health problems emerged in the exercise training
groups. These health problems were not directly related to physical
exertion. In the final study 23 and 7% of the exercise tests in
men and women, respectively, were prematurely terminated because
of cardiac arrhythmia or ST segment depressions. Using various study
designs and methods the effects of physical training on cardiovascular
fitness were found to be beneficial among the four different samples
of elderly people. High exercise capacity was found to be strongly
and independently associated with decreased mortality among elderly
men and women. Exercise testing provides information on the risk
of death that is incremental to clinical data and traditional risk
factors for death. Cardiovascular monitoring during exercise testing
is recommended as a safety precaution. Cardio- or cerebrovascular
health problems can occur during exercise training programmes involving
elderly people, although they may not be directly related to physical
exertion. The dose-response relationships in relation to physical
exercise among elderly people remain in need of further clarification
in population-based trials.
KEY
WORDS: Benefits and hazards of exercise, cardiovascular fitness,
older people, exercise testing, predictive value, arrhythmia, ST
segment depressions.
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INTRODUCTION |
"Ageing
is the process that converts fit adults into frailer adults with
increased risk of illness, injury, and death" (Miller, 1999).
Ageing is neither a developmental process nor a disease, although
a great proportion of older people have some overt or subclinical
disease. It is useful but difficult to distinguish whether the age-related
changes observed in the human beings are due to ageing itself or
consequences of life- style factors, disease processes or genetic
factors. These statements offer a basic definition of ageing. However,
ageing is a process which individuals encounter in various ways
and at different speeds. Ageing also influences different organ
systems in varying ways and magnitudes. It is apparent that age-related
changes in various physiological characteristics, for example, in
cardiovascular fitness vary between the time periods (age cohorts).
Studies on these age-related changes encounter problems of cohort
and time-of measurement effects, and selection bias due to health
(Ingram, 1999).
Physical exercise has effects counter those of age on many body
structures and functions (Shephard, 1997a).
Cardiovascular fitness, for example, has been found to be markedly
higher among older endurance- trained men and women than among older
less active subjects (Fitzgerald et al., 1997;
Wilson and Tanaka, 2000).
Cross-sectional comparisons in aerobic capacity between age groups
usually tend to find minimal age- related changes in aerobic capacity
because of enhanced selection by health and level of fitness in
surviving older age groups. Older people who are fitter and healthier
are more likely to survive than their frailer counterparts. Katzel
et al. (2001)
reported that longitudinal reductions in the absolute VO2max
(in ml·kg-1·min-1) among older endurance athletes
were two to three times as large as those predicted by cross-sectional
analyses or those found longitudinally in their sedentary counterparts.
However, Saltin (1986)
have suggested that the decline in VO2max in endurance
athletes is comparable regardless of the athletes are studied cross-sectionally
or longitudinally.
Since the publication of the origin of the species by Charles Darwin
in 1859 it has been claimed that the fittest individuals of different
species survive the longest (Balady, 2002;
Darwin, 1859).
This survival advantage among physically active and fit individuals
has been thought to be true in older people (Goraya et al., 2000).
Considerable beneficial effects of physical exercise on physical
performance have been found in numerous longitudinal surveys and
training studies. Recent training studies suggest that adaptation
to endurance training is also preserved among the oldest old people
(Binder et al., 2002;
Malbut et al., 2002;
Vaitkevicius et al., 2002).
It has been suggested that the magnitude of the gain in aerobic
capacity by endurance training is related to age of subject, duration
of exercise bouts, length of training programme, and pretraining
VO2max (Green and Crouse, 1995).
Most of these cross-sectional and longitudinal studies on cardiovascular
fitness have, however, been performed among selected physically
active and healthy older people. More data are needed to confirm
the beneficial effects of training among the oldest old people aged
75 and over, especially among women, and among those having disabilities.
Strenuous exercise can also have deleterious effects. Few researchers
have reported any adverse effects among elderly people both either
during acute exhaustive exercise or prolonged physical training.
Most of the adverse effects reported have been minor musculoskeletal
problems. A large proportion of these studies, again, have been
conducted among healthy people below age 75. Subjects with health
problems have usually been excluded.
The standard guidelines issued by American College of Sports Medicine
(ACSM, 2000)
in exercise testing and prescription differ in a few details between
elderly and younger people. Exercise testing under the supervision
of a physician is recommended for most elderly people during maximal
tests and prior to participation in vigorous exercise (ACSM,2000;
Fletcher et al., 1995).
However, the value of exercise testing both for health screening
and predictive purposes among elderly people has been questioned
(Gill et al., 2000).
It has been suggested that the safety margin in the case of physical
exercise is narrower among older than younger people (Kallinen and
Alen, 1995). Among older individuals the
adverse effects of physical exercise may occur with a lower dose
of exercise than among younger individuals. It may also be that
older people benefit proportionally more from lower doses of exercise.
A relatively few randomised controlled trials have been performed
that address the issue of dose-response relationships among elderly
people.
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REVIEW
OF THE LITERATURE |
The
factors behind age-related decline in physical performance
Muscular
strength
Muscular strength is dependant on the amount of the contracting proteins
actin and myosin present in the muscles. Loss of these proteins and
muscle mass (sarcopenia) starts at the age of 25 and is mainly due
to loss and reduction in size of type II muscle fibres. The fibres
can change during ageing to types which are neither strictly type
I nor type II (Andersen et al., 1999).
The mean reduction in the area of the vastus lateralis muscle is 40%
between the ages of 20 and 80 (Lexell, 1995).
The most apparent decrease in isometric muscle strength is seen after
the age of 50 (Larsson and Karlsson, 1978).
A similar decline has been reported in isokinetic muscle force (Stanley
and Taylor, 1993).
The loss of strength seems to proceed more rapidly in women than in
men, and is greatest around the menopause. Female sex steroids may
play an important role in muscle strength in post-menopausal women
(Sipilä et al., 2001;
Skelton et al., 1999).
Additionally, local growth factors (GH/IGF-I) influence muscle repair,
adaptation and other age- related changes in muscles and their function
(Harridge, 2003).
Muscle satellite cells can form new muscle fibres in cases of muscular
trauma and also in response to mechanical stimuli (Seale and Rudnicki,
2000).
The age-related changes in skeletal muscle are listed in Table
1.
Older persons who engage in resistance exercise have higher muscle
mass and strength than their sedentary counterparts (Sipilä and Suominen,
1993;
1994).
Gains in muscular strength greater than 100% have been reported in
elderly people after only a few months' strength training (Charette
et al., 1991;
Fiatarone et al., 1990;
1994; Frontera, 1988).
Strength training has also increased muscle cross-sectional area in
elderly people (Fiatarone, 1990; Frontera et al., 1988). However, other studies have reported considerably lower
changes in muscular strength in elderly people after comparable training
intensities and durations (Rice et al., 1993;
Sipilä et al., 1996; Skelton et al., 1995).
The differences in the gain in muscular strength between these studies
may be due to differences in the measure of muscular strength used
(1 RM versus isometric muscular strength measurements). Increase in
the cross-sectional areas of all fibre types (I, IIA, and IIB) together
with a decrease in percentage body fat have been detected after 16
weeks high-intensity resistance training (Hagerman et al., 2000). It has been suggested that age, sex, specific chronic
conditions, depression, dementia, nutritional status and functional
impairment do not influence adaptation to strength training (ACSM,
1998).
Cardiovascular fitness
The supply of oxygen to the contracting muscles is the most important
limiting factor in endurance exercise lasting longer than minute or
two. Oxygen uptake is a product of cardiac output and peripheral arteriovenous
oxygen difference. Therefore maximal oxygen uptake (VO2max)
is the principal measure of aerobic capacity and cardiovascular fitness.
Sustained muscular work leads to hydrogen ion accumulation inside
the muscle and a decrease in intramuscular pH. Larger concentrations
of inorganic phosphate and a reduced potassium concentration inside
muscle cells cause decreased cross-bridge formation, decreased muscle
membrane excitation and finally weakness of the muscles.
The ability to perform sustained muscular work is also dependant on
the available energy resources, primarily on the muscular stores of
glycogen. Although stored fat is substantially used for production
of high energy phosphates, glycogen depletion leads eventually to
muscle fatigue in prolonged muscular work. The supply of oxygen for
oxidation of fat and glycogen and the removal of carbon dioxide are
dependant on the cardiovascular (blood flow) and respiratory functions
(ventilation).
Several changes occur in the human cardiovascular system during ageing.
It is difficult to distinguish whether these changes are related to
ageing per se or to the effects of pathological processes in the cardiovascular
system, reduced total metabolic tissue mass or physical inactivity.
The age-related changes in the human cardiovascular system are listed
in Table 2. The most apparent
effects of ageing on the human heart are elevated cardiac diastolic
volumes and decreased myocardial contractility and maximal heart rates
during heavy exercise (Fleg et al., 1995).
These alterations are thought to be due to changes in the sympathetic
nervous system. An increase in the plasma levels of norepinephrine
and epinephrine together with reduced responses to beta-adrenergic
stimulation are seen in older subjects (Lakatta, 1993).
The increased expression of atrial natriuretic peptides, a marker
of increased atrial load and dilatation, is reported to increase in
the senescent rodent heart (Younes et al., 1995).
Maximal oxygen uptake decreases inevitably with age. This decline
in VO2max is of the order of 5-22% per decade and 0.28
to 1.32 ml·kg-1·min-1 per year (Kasch et al.,
1999; Posner et al., 1995). A similar decline in aerobic capacity has been reported
for both sexes (Fleg and Lakatta, 1988). It has been suggested that the rate of decline in maximal
oxygen uptake by age is 50% less in endurance-trained than sedentary
adults (Heath et al., 1981).
Declined physical activity and reduced muscle mass account for a large
proportion of the reduced maximal oxygen uptake observed during ageing
(Ogawa et al., 1992). A smaller stroke volume, decreased maximal heart rate
and arteriovenous oxygen difference are also involved in this decline
(Fleg, 1994). A twenty-percent lower citrate synthase activity, a
marker of aerobic metabolism, has been reported in the muscle of older
untrained men aged 58-68 years men compared to corresponding groups
of men aged 21 to 33 years (Coggan et al., 1993). In some studies older subjects have reversed a marked
proportion of their reduced muscle respiratory capacity by endurance
exercise training (Coggan et al., 1993; Meredith et al., 1989). Adaptation in both cardiac function and the peripheral
circulation has been detected during exercise training among elderly
persons (Beere et al., 1999; Stratton et al., 1994), but peripheral factors may play a major role in adaptation
to endurance training in older people (Meredith et al., 1989). Regular intensive endurance exercise has been found
to be associated with higher growth hormone and testosterone levels
among older runners than their sedentary peers (Hurel et al., 1999). Both hormones are important in preserving fat-free mass
during ageing.
Respiratory
capacity
It is generally believed that respiratory function does not limit
the individual's performance in endurance exercise except in top level
athletes (Harms and Stager, 1995). This may not be the case among elderly people.
Detrimental changes are seen during ageing in the chest wall, the
bronchial tree, and the lungs (Table
3). These are followed by changes in pulmonary functions e.g.
compliance, static lung volumes, pulmonary dynamics, gas exchange,
and the oxygen cost of breathing. In some of the oldest persons the
ventilatory equivalent, which describes the volume of air ventilated
and needed for one litre of oxygen consumed, may exceed 30 l·l-1.
During physical exertion an elderly person may soon approach the dyspnoea
threshold in peak tidal volume, which is about 50% of vital capacity
(Shephard, 1997a).
Diseases
Ageing is associated with disabling chronic diseases, co-morbidity
being quite common. According a recent survey carried out among the
Finnish population, 81% of people aged 65 or older have almost one
chronic disease (Aromaa and Koskinen, 2002). Thirty percent and 21% of the older men and
women have clinically evident myocardial infarction or angina pectoris.
In addition to overt coronary heart disease, a large proportion of
elderly people may have a symptomless coronary heart disease which
it may be possible to detect by exercise ECG and/or thallium scan
(Gerstenblith et al., 1980).The prevalence of chronic obstructive pulmonary disease
in Finnish older people, according to spirometry, was 27% among older
men and 14% among women, respectively. Hip or knee osteoarthritis
is evident among 16 to 32% of older men and women (Aromaa and Koskinen,
2002). Psychological factors and cognitive impairment
may influence further the management of daily tasks among elderly
people (Laukkanen et al., 1993). Poor health was among the commonest obstacles to physical
exercise reported in interviews with Finnish elderly men and women
(Hirvensalo et al., 1998).
Arteriosclerosis of the coronary arteries decreases coronary blood
flow and cause ischaemia in cardiac muscle and deterioration of the
pumping power of the ventricles. Under extreme conditions necrosis
of the cardiac muscle (myocardial infarction) and a markedly decreased
ejection fraction (cardiac failure) follow. The symptoms limiting
exercise tolerance in ischaemic heart disease are chest pain and/or
dyspnoea. Low creatine phosphate concentrations, high phosphate, high
lactate, and low pH values are seen in the skeletal muscles of heart-failure
patients during exercise (Wilson et al., 1988). Patients with heart failure have increased sympathetic
drive, skeletal and respiratory muscle atrophy and/or weakness, and
hyperkinetic cardiovascular responses to physical exercise together
with hyperventilation (Chua et al., 1995; Jondeau et al., 1992; Linderholm et al., 1969;
Lindsay et al., 1996;
Meyer et al., 2001).
The limiting physiological factors during exercise are similar in
patients with pulmonary diseases and cardiovascular diseases. An altered
ventilation perfusion ratio causes a decrease in PaO2.
Pulmonary hypertension and overload of the myocardium of the right
ventricle are usually seen in severe pulmonary emphysema. Also, found
among these patients there is reduced skeletal and inspiratory muscle
strength together with impaired aerobic capacity of the muscles (Jones
and Killian, 2000). In mild chronic bronchitis and bronchial asthma there
is no decrease in PaO2, and the ventilation perfusion ratio
could even improve during physical exertion. In many cases the response
to exercise is variable among patients with respiratory disorders
and these responses are difficult to predict by measuring pulmonary
capacity at rest (Jones and Killian, 2000).
Patients with musculoskeletal disorders may be obese, and have decreased
muscular strength, endurance and cardiovascular fitness (Ries et al., 1995). A higher prevalence of coronary heart disease has been
found among patients assessed before total knee arthroplasty (Philbin,
1995).
Medication
Age and morbidity increase drug use. Elderly women use medication
more than elderly men. Diuretics, cardiac glycosides, nitroglycerides
and beta-blocking agents as well as analgesics and sedatives are the
types of medication most commonly used among the Finnish elderly (Laukkanen
et al., 1992). Polypharmacia is also common among elderly people (Laukkanen
et al., 1992). Medication may either increase or decrease physical
effort tolerance.
Beta-adrenoceptor antagonists (beta-blocking agents) block the β-
receptors through which the actions of the sympathetic nervous system
are mediated. Two distinct receptors have been found: beta-1- and
beta-2 -receptors. Non-selective - blockers attenuate both beta-1-
and beta-2-receptor stimulation leading to decreased heart rate, myocardial
contractility, glycogenolysis, brochodilatation, vasodilatation and
possibly fatty acid mobilisation during exercise. These alterations
are advantageous for the patients with coronary heart disease as they
decrease the myocardial oxygen demand and increase the myocardial
ischaemia threshold. Non-selective beta-blocking agents may lead to
central and peripheral limitations of effort tolerance and increased
ratings of perceived exertion to external load (Head, 1999).
Selective beta-1-blockers have minor negative effects on bronchial
dilatation, vasodilatation and fatty acid mobilisation during exercise.
Their effects, however, are dose-related, higher doses also having
beta-2-blocking effects.
Digitalis increases myocardial contractility by increasing intracellular
sodium and calcium (Peel and Mossberg, 1995). This drug is used to treat patients with heart failure
and atrial fibrillation to improve left ventricular performance. Digitalis
has a narrow therapeutic margin, higher doses causing bradycardia,
arrhythmia and fatigue. Digitalis provokes ST segment depression in
the ECG, misleadingly indicating myocardial ischaemia. Diuretics increase
the excretion of the electrolytes sodium and potassium, and water
by the kidneys. A decrease in blood volume results and therefore these
drugs are beneficial in hypertension and heart failure. Hypokalemia
related to diuretic medication can cause cardiac arrhythmia and muscle
fatigue during physical exercise (Peel and Mossberg, 1995).
Calcium antagonists, ACE inhibitors, alpha-1 antagonists and centrally
acting alpha-agonists decrease both systolic and diastolic blood pressure
and are thus used in hypertension. No significant effects of calcium
antagonist and ACE inhibitor medications on maximal oxygen uptake
and work rate have been found with among relatively asymptomatic persons.
Among patients with marked coronary heart disease or with heart failure
these drugs improve hemodynamics and physical effort tolerance. ACE
inhibitor use has been found to be associated with a lower decline
in muscular strength among elderly hypertensive subjects (Onder et
al., 2002).
Nitrates dilate both the system and coronary veins and arteries, reducing
the preload of the heart and increasing coronary circulation. These
effects are advantageous in patients with coronary heart disease as
they increase their endurance work performance (Peel and Mossberg,
1995).
Physical activity
Heredity (Bouchard and Rankinen, 2001), physical activity, body composition and other factors
such as life-style and personality contribute to health and health-related
fitness (Bouchard and Shephard, 1994). Among physically active individuals the reserve capacity
will remain high enough for the performance of the activities of daily
living. It has been argued that the decline in the absolute values
in cardiovascular fitness is more gentle among physically active than
among sedentary persons (Heath et al., 1981; Kasch et al., 1993;1999;
Ogawa et al., 1992; Rogers et al., 1990). A large body of evidence exists to show that physical
activity is associated with a reduction in all-cause mortality, cardiovascular
disease, incidence of type 2 diabetes mellitus, and incidence of colon
cancer and osteoporosis (Kesäniemi et al., 2001). A high level of physical activity has been shown to
be associated with decreased risk of death in older people in several
studies (Bijnen et al., 1999; Glass et al., 1999; Kaplan et al., 1987; Paffenbarger et al., 1986). It also seems evident that regular physical exercise
protects against the triggering of cardiac events during vigorous
exercise (Mittleman et al., 1993; Willich et al., 1993). On the other hand social and productive activities,
such as church attendance, participation in social groups, shopping
and gardening have been found to lower the risk of death as much as
fitness activities among people aged 65 and older (Glass et al., 1999). Numerous other factors including genetic and socioeconomic
factors are also involved in survival (Kujala et al., 2002; Lantz et al., 1998).
A polarisation phenomenon has been found in physical activity habits
among elderly people with ageing (Marin, 1988). The proportion of physically very active older people
tends to remain almost the same or to increase slightly during the
later years of life. The remainder of the older population tend to
reduce the amount of their physical activity. The proportion of 75-
84-old Finnish men exercising several times per week to the point
of perspiring and heavy breathing was found to be about 17 percent
(Hirvensalo et al., 1998). This proportion fell to about 7% over an 8-year follow-up.
This declining trend in physical activity has also been seen among
women. In a recent extensive survey on the health of Finns aged 30
years and older the most physically active individuals were men aged
65 to 74 years (Aromaa and Koskinen, 2002). Forty-three per cent of the men in this age
group exercised at least 4 times per week to the point of light breathing
and perspiring. The least physically active were women aged 75 to
84 years of whom fewer than 15% exercised so as to induce light breathing
and perspiring at least four times per week. A declining proportion
of people were physically active after the age of 74 in both sexes.
Cardiovascular
benefits of physical exercise
Effects of physical training on cardiovascular fitness
A marked higher aerobic capacity has been found in several studies
comparing older endurance-trained persons with their sedentary counterparts.
Inconsistency in the results continues to characterize the results
of cross-sectional studies concerning the rate of decline in aerobic
capacity between physically active persons and sedentary persons.
Fitzgerald et al. (1997) found a steeper decline in absolute maximal oxygen uptake
among endurance-trained compared to sedentary women. Jackson et al.
(1996)
found no difference in the rate of this decline between two corresponding
groups of women. In a large meta-analysis this was also true among
men (Wilson and Tanaka, 2000).
No difference in the relative decline of aerobic capacity has been
detected between differently physically active groups of women or
men (Fitzgerald et al., 1997;
Wilson and Tanaka, 2000). Pollock et al. (1987),
however, in a 10-year longitudinal study of runners aged 50 to 82
years reported a 13 percent reduction in maximal oxygen uptake among
runners with reduced training intensity compared to a 2 percent loss
in maximal oxygen uptake in a group of runners maintaining their habitual
training intensity. Similar results have been found in other longitudinal
studies among highly physically active subjects (Kasch et al., 1993;
1999; Trappe et al., 1996; Katzel et al., 2001). In the studies by Kasch et al., a lower decline in maximal
oxygen uptake expressed in ml·min-1·kg-1 body
weight was caused by a marked reduction in body weight during the
intervention.
Katzel et al. (2001) reported that the longitudinal reductions in absolute
VO2max (in ml·min-1·kg-1) were two
to three times as large as those predicted by cross-sectional analyses
or those found longitudinally in their sedentary counterparts. The
relative reduction in aerobic capacity was 22% in older endurance
male athletes compared to 14% in sedentary men. The inconsistency
of the results in studies comparing the decline in aerobic capacity
between physically active and sedentary subjects may be due to differences
in the training levels with ageing. It is also obvious that different
conclusions can be drawn according to whether the absolute reductions
in aerobic capacity are expressed in absolute values (ml·min-1·kg-1
or l·min-1), or as relative decline in aerobic capacity
expressed as percentages of the baseline values.
It has been suggested that almost 100% of the age-related decline
in aerobic capacity accumulated during 30 years among middle-aged
men could be reversed by 6 months' endurance training (McGuire et
al., 2001). Up to what age such a kind of reversal in aerobic capacity
is possible remains unclear. Considerable increases (up to 38%) in
cardiovascular fitness and other positive effects have been reported
during endurance exercise programmes among older individuals. Only
a few studies, where the exercise dose has been insufficient, have
reported no change or even a decrease in cardiovascular fitness with
endurance exercise training (Green and Crouse, 1995). The magnitude of the gain in aerobic capacity is dependant
on the initial aerobic capacity and age of the subject, and on the
duration of the exercise bouts/training programme. The youngest older
subjects with the lowest baseline aerobic capacity increased their
aerobic capacity most after training with exercise bouts and programme
of sufficient duration (Green and Crouse, 1995). However, most studies have been performed among men
and subjects younger than 75 years of age excluding subjects with
disabilities.
Recent endurance training studies have also been performed among the
oldest old and among frail subjects (Binder et al., 2002; Malbut et al., 2002; Vaitkevicius et al., 2002).
Binder et al.(2002) found a 13% increase in VO2peak
(95% CI for the improvement 0.9 to 3.6 ml·min-1·kg-1)
in 9 months' intensive exercise training compared to no increase in
VO2peak after a 9-month low-intensity home exercise program
among 115 sedentary men and women aged 83 years (SD, ±4 years) with
mild to moderate physical frailty. In this study 15% percent of the
target group was excluded from the training programmes because they
were considered too frail or ill for vigorous exercise. Furthermore,
27% of the randomized participants dropped out of the study because
of medical problems unrelated to the training. Malbut et al. (2002) found a 15% increase in VO2max after 24 weeks'
endurance training in 12 elderly women aged 79 to 91 years, but no
change in 9 men. The men in the study by Malbut et al. had a marked
higher pretraining VO2max than women (21.8 vs. 13.8 ml·min-1·kg-1)
and therefore were not expected to show a large gain in aerobic capacity
with endurance exercise training. A six-month community-based moderate
endurance training programme resulted in a 6.5% increase in VO2peak
among 22 men and women aged 80 to 92 years in the study by Vaitkevicius
et al. (2002).
In the latter study the gain in aerobic capacity might have been even
more limited had the subjects with submaximal exercise test results
after training not been excluded.
Age, sex, specific chronic conditions, depressions, dementia, nutritional
status and functional impairment have not been shown to influence
adaptation to strength training (ACSM 1998).
Some researchers (Hepple et al., 1997;
Hagerman et al., 2000)
have found beneficial effects of strength training on cardiovascular
fitness among elderly people while others have not found any statistically
significant differences in cardiovascular fitness with resistance
training (Hagberg et al., 1989;
Pollock et al., 1991).
Value of exercise-test result including exercise capacity in predicting
mortality among elderly people
Exercise testing is widely used to diagnose cardiovascular disease
or to evaluate its seriousness. Exercise testing is also recommended
for screening purposes for older people starting a vigorous exercise
training program (ACSM, 2000)
to avoid exercise-triggered cardiovascular complications. Exercise
test- results may further have prognostic value with respect to cardiovascular
morbidity and mortality as well as all-cause mortality. Exercise capacity,
exercise duration, positive exercise electrocardiogram, change in
systolic blood pressure during exercise, marked cardiac arrhythmia,
and heart-rate recovery have been found to be associated with the
risk of death and cardiovascular morbidity even among apparently healthy
and asymptomatic populations (Blair et al., 1995;
Curfman and Hillis, 2003;
Cole et al., 1999;
Era et al., 2001;
Glover, 1984; Goraya et al., 2000;
Gulati et al., 2003;
Jouven, 2000; Lakka et al., 1994;
McHenry et al., 1984;
Messinger-Rapport et al., 2003;
Myers et al., 2002; Rywik et al., 1998;
Sandvik. et al., 1993). However, relatively few studies have been
examined this question among older people and among both sexes (Era
et al., 2001;
Goraya et al., 2000;
Messinger-Rapport et al., 2003).
In the study by Goraya et al. (2000) after adjusting for clinical factors
high workload in the treadmill test was the only factor associated
with a decreased risk for death and cardiac events among the elderly
subjects. One MET (metabolic unit) increase in workload resulted in
an 18% reduction in risk for death in elderly persons and a 20% reduction
in risk in younger persons. It was concluded that the treadmill exercise
testing provided prognostic information that was incremental to the
clinical data. The results also showed that the prognostic effect
of workload in elderly subjects was of the same magnitude as in younger
subjects. However, 72% of the exercise tests among the older participants
were done for either the evaluation of documented coronary artery
disease or its diagnosis. The participants were selected because of
their high likelihood of having coronary heart disease. It is thus
difficult to generalise the results of this study across the "normal"
elderly population.
It has been suggested that the association of cardiac arrhythmia with
subsequent coronary events among apparently healthy older people is
weak (Fleg et al., 1993). However, in asymptomatic middle-aged men frequent premature
ventricular depolarisations were associated with increased risk of
death from cardiovascular causes in a mean follow-up of 23 years (Jouven
et al., 2000). It is widely accepted that severe cardiac arrhythmia
in relation to coronary heart disease and ischemia increase the risk
of subsequent cardiac morbidity and mortality. An ischemic ST segment
depression is a predictor of cardiovascular morbidity and mortality
(Bruce et al., 1980).
Changes in the ST segment are also usually seen in older people's
exercise ECGs. The occurrence of ST segment changes is highly predictive
of coronary artery disease in subjects with typical symptoms of the
disease (angina pectoris). The predictive value, on the other hand,
is low when the symptoms are not typical. It is also obvious that
the possibility of having both a coronary heart disease and a positive
exercise ECG is higher among population with high prevalence of disease
i.e. among older people. In a population study Hedbad et al. (1989)
found increased mortality among elderly men with ST segment depressions
in their 24 hour ambulatory ECG recording. The risk of death was increased
also among elderly men with non-symptomatic ST depressions. A high
level of physical activity is associated with reduced risk for symptomatic
ischemic heart disease. However, in the study of Katzel et al. (1998)
the prevalence of exercise- induced silent myocardial ischemia in
a maximal exercise test and in tomographic thallium scintigraphy was
comparable among master male athletes and among healthy untrained
men with no history of ischemic heart disease.
The role and use of exercise testing among elderly people has been
questioned by some authors (Gill et al., 2000;
Fiatarone Singh, 2002).
These authors criticize the routine use of exercise testing among
elderly people, starting with a vigorous exercise training programme,
as recommended by ACSM and AHA. The difference between vigorous and
moderate exercise may be difficult to determine. Furthermore, the
interpretation of exercise test results is problematic among elderly
people because of non-specific signs and symptoms during testing.
Intensive screening by exercise testing and other methods usually
excludes a marked proportion elderly people from participating an
exercise training programmes. In this way the oldest and frailest
people who may obtain the largest benefit from physical exercise may
be excluded from exercise training programmes (Fiatarone Singh, 2002).
Possible harmful effects of physical exercise
Effects
of acute physical exercise on cardiac function
During heavy exercise plasma ionic concentration of potassium can
double compared to the concentration at rest, the decrease in pH could
be 0.4 units and increase in plasma catecholamines 15-fold (Paterson,
1996).
Pulse rate and systolic blood pressure increase, while diastolic blood
pressure tends to decrease slightly. In elderly person the capacity
of the heart to increase the heart rate is limited. An aged heart
compensates for the decreased left ventricular filling rate in the
early diastole by enhanced atrial contraction (Swinne et al., 1992).
The left ventricular diastolic volume normalized for body surface
area does not differ much between younger and older healthy persons
in the resting supine position (Fleg et al., 1995).
However, during heavy exercise the diastolic volume of an elderly
persons' heart increases suit to the cardiac minute volume to the
demands of the working muscles. In younger persons diastolic volume
drops to the seated rest level during exhaustive exercise (Fleg et
al., 1995). The maximal ejection fraction during exhaustive upright
exercise decreases with age due to difficulties in the ability to
reduce end-systolic volume (Fleg et al., 1995).
Under the extreme biochemical conditions described above cardiac arrhythmia
can be provoked. The heart is, however, protected against this chemical
stress during exercise by mechanisms which are unclear. The heart
seems to be at greatest risk in the post-exercise period when plasma
potassium is low and plasma catecholamines are still at a high level
(Paterson, 1996).
It has been noticed that cardiac arrhythmia in physical exercise increase
with age (Mayuga et al., 1996;
Fleg, 1994). Most (about 80%) fatal cardiac arrhythmias are due to
coronary atherosclerosis among adult population. Other causes of fatal
arrhythmias include cardiomyopathy (10-15%) and among others (<
5%) are primary electrical and genetic ion-channel abnormalities,
valvular or congenital heart disease (Huikuri et al., 2001).
General aspects of safety in physical exercise
Acute physical exercise increases the risk of cardiovascular events
during the physical effort. The increase in risk is compensated for
by a decrease in cardiovascular risk at other times. It is evident
that regular physical exercise has beneficial effects on morbidity,
mortality, functional decline, mobility, disability, coronary heart
disease, and contributes to increase in active life expectancy (Gill
et al., 2000). However, an important question is whether the immediate
increase in risk during physical effort is age-related. In the epidemiological
study by Vuori et al. (1995) both the absolute number of deaths during participation
in various physical activities and the risk relative to activity were
lower among persons aged 50 to 69 years than in middle-aged people.
In contrast Mittleman et al. (1993) found that among people aged 70 years and over the relative
risk of onset of myocardial infarction was over double that of younger
age groups (< 50 years, 50 to 69 years), although this result did
not reach statistical significance in the chi-square test. The researchers
also found that the induction time for the onset of myocardial infarction
was less than one hour. Furthermore, the corresponding relative risk
of persons who were habitually sedentary was 100 compared to 2 among
persons engaging in strenuous physical exertion 5 times or more per
week (Mittleman, 1993). Similar results were reported by Willich et al. (1993).
Deposition of cholesterol, macrophage infiltration, enlargement of
the necrotic core of the plaque, and the accumulation of erythrocyte
membranes in an atherosclerotic plaque increase the risk of plaque
rupture (Kolodgie et al., 2003). Acute risk factors for exercise-induced cardiac adverse
effects are hemodynamic reactivity, hemostatic reactivity and vasoreactivity
(Muller et al., 1994). The physical and mental stress quite often serves as
an initial triggering mechanism producing hemodynamic changes which
leads finally to plaque rupture in the coronary arteries (Muller et
al., 1989). The end-point of this complex cascade would be myocardial
infarction, cardiac arrhythmia or sudden cardiac death.
Surprisingly few adverse effects during exercise interventions among
elderly people have been reported (Belman and Gaesser, 1991; Binder et al., 2002;
Buccola and Stone, 1975; Carroll et al., 1992; Cunningham et al., 1987;
Ehsani et al., 1991; Hamdorf et al., 1992;
Kohrt et al., 1991; Malbut et al., 2002; Puggaard, 2000;
Seals et al., 1984; Spina et al., 1993; Suominen et al., 1977a;
1977b;
Tzankoff et al., 1972;
Vaitkevicius et al., 2002). Most of these effects have been related to musculoskeletal
problems. In strength testing Shaw et al. (1995)
and Pollock et al. (1991)
found some musculoskeletal injuries related to 1RM strength testing.
In the study by Pollock et al. (1991)
19% of the elderly subjects sustained a joint injury during 1RM strength
testing while 57% of the subjects who began to jog incurred an injury.
Strength training resulted in only 2 injuries in 23 subjects (8.7%)
and walking in only one injury in 21 subjects (4.8%). A few authors
have reported harmful cardiac effects following exercise training
among elderly people (DeVries, 1970; Ehsani et al., 1991).
The best way to avoid cardiovascular complications and musculoskeletal
problems is prevention. Pre-exercise screening by medical examination
is important in this respect. The content of a clinical examination
prior to exercise testing and physical training programmes is presented
in Table 4. ECG and some blood
tests may also be of value in such a pre-exercise evaluation (ACSM,
2000).
Plasma N-ANP can be used as a marker of left ventricular dysfunction
(Lerman, 1993). The role of plasma C-ANP in the assessment of cardiac
function needs to be clarified. The ACSM recommends exercise testing
under supervision of the physician in the case of older or sick people
starting a heavy exercise training program (ACSM,
2000).
Exercise testing and its safety
The great individual variation in physical capacity and health among
elderly people calls for an individual assessment of test modalities
(ACSM, 1995;
Spirduso, 1995). Methods of assessing endurance capacity can include
self-reports, interviews or observations. Measuring cardiovascular
fitness can include submaximal or maximal physical capacity tests.
During maximal tests the measurement of direct oxygen uptake, carbon
dioxide production, ventilation and respiratory exchange ratio (RER)
produces accurate measures for aerobic capacity. The value of submaximal
tests is limited due to wide individual variation in the maximal heart
rates (ACSM, 1995).
The most common methods used to asses cardiovascular function during
exercise are 12-lead ECG and blood pressure monitoring. Supervision
by a physician is recommended when maximal testing is performed with
people at high risk (older or sick people) (ACSM,
2000).
Exercise testing is used both for diagnostic purposes and to assess
physical performance. The diagnostic and prognostic variables generally
used during or after exercise testing are listed Table
5. A > 1mm horizontal or downsloping ST segment depression
in the early phases of exercise, angina pectoris, marked ventricular
arrhythmia, inadequate blood-pressure or heart rate responses during
exercise are obvious markers of cardiovascular disease and mean a
poor prognosis (Curfman and Hillis, 2003).
Most of the studies related to exercise testing in elderly people
have been performed among selected groups of healthy and physically
fit elderly subjects. The adverse effects of heavy physical exercise
in the form of exercise testing have been found to be minimal in these
studies. Morbidity rates of 0 to 232 and mortality rates of 0 to 2.5
per 10 000 exercise tests have been reported (ACSM,
2000).
These complication rates depend much on the age and health of the
subjects tested. The safety of exercise testing has been studied specifically
in the study by Gibbons et al. (1989). It can be calculated from the data given in this study
that the complication rate among subjects older than 60 years was
10 times higher than that among the younger subjects. Gibbons et al.
(1989) found that the complication rate decreased with time
after a cooling-down period phase was added to the exercise protocol.
They also found that most of the complications emerged in the immediate
or late recovery period (Gibbons et al., 1989).
The American College of Sports Medicine has laid down widely used
guidelines for exercise testing and prescription (ACSM,
1995;
2000).
According to these recommendations medical clearance is advised prior
to maximal exercise testing or participation in vigorous exercise.
However, no specific indications for exercise test termination are
given for the elderly population. The test modalities need to be modified
for elderly populations because of the physiological effects of ageing
and concomitant medical problems. It is recommended that exercise
testing is started at low intensity, with small increments in work
rate and longer stages. Among elderly individuals it is deemed best
to keep the total exercise test time between 8 and 12 minutes. The
cycle ergometer test is the preferred exercise test loading type (ACSM,
1995).
The basic questions related to the safety of exercise testing are:
When should the test not be performed? When should a test be stopped?
Most of the contraindications for testing and indications for stopping
a test are related to cardiovascular disease and cardiovascular disturbances.
The contra-indications for exercise testing and indications for test
termination are presented in Tables
6 and 7.
Physical training and its safety
The responses to physical exercise are either beneficial or harmful.
Improvement in cardio-
vascular fitness and cardiovascular health are among the beneficial
effects of an appropriate dose of exercise. High intensity endurance
exercise is associated with cardiovascular complications such as cardiac
arrhythmia, cardiac arrest and sudden cardiac death. Exercise of high
frequency and long duration can provoke musculoskeletal problems.
Exercise type is also important with respect to responses. Aerobic
exercise causes changes in the cardiovascular and metabolic body systems
whereas anaerobic strength training imposes stress mainly on skeletal
muscle. On the other hand the magnitude of stress should be sufficient
to induce a process of adaptation in the body's systems, i.e. improvement
in cardiovascular fitness or muscular strength.
The intensity of exercise can be defined in absolute terms or relative
to the individual's maximal initial level. Usually the level of intensity
in endurance exercise is expressed relative to maximal oxygen uptake
(i.e. 50-85% VO2max). The corresponding training heart
rates are used by plotting them against the oxygen uptake level during
an exercise test (direct method). The direct method is considered
to be the best choice when setting an appropriate training intensity
for persons with low fitness levels, for those with cardiovascular
or pulmonary disease, and for those on some types of medication (e.g.,
beta-blockers). During exercise testing a safe level of exercise intensity
can be established before the adverse effects of exercise arise (ACSM,
2000).
Training heart rates expressed as a percentage of the heart rate reserve
(i.e. 50-85% of heart rate reserve, HRR) plus resting heart rate (Karvonen
et al., 1957) can also be used. The heart rate reserve is calculated
by subtracting the maximal heart rate by the resting heart rate. Another
way to calculate the training heart rate is to express it as a percentage
of the maximal heart rate (i.e. 60-90% of the maximal heart rate,
HRmax). The ACSM 2000
recommends the HRR method, which is comparable to the relative values
of maximal oxygen uptake. However, among elderly people some authors
favour using the percentage of maximal heart rate as it has been found
to be accurately related to oxygen uptake in older women and men (Kohrt
et al., 1993; Panton et al., 1996). Subjective ratings (rating of perceived exertion, RPE;
Borg-scaling 6-20, Borg, 1970) of the intensity of exercise are also used alone or in
the combination with other methods.
Muscular strength is best trained using near maximal weights with
few repetitions while muscular endurance can be improved by light
weights with a greater number of repetitions. Recent guidelines for
resistance training among elderly people recommend 8-10 exercises
of all the major muscle groups repeated 10-15 repetitions with RPE'
s of 12 to 13 (somewhat hard) and a training frequency of two times
per week. The resistance training should be at low level during the
first 8 weeks to allow adaptation of connective tissues. To maintain
adherence to the training program resistance training exercise sessions
should not last over 60 minutes. Normal breathing pattern should be
maintained while exercising to avoid an excessive rise in systolic
and diastolic blood pressure (ACSM, 2000).
In addition, to appropriate modes, intensity, duration, frequency
and progression of exercise, every exercise session should include
warm-up and cooling down exercises to avoid harmful cardiac or musculoskeletal
adverse effects (ACSM, 2000).
It has been suggested that the gain in aerobic capacity among elderly
people achieved by endurance training is dependant on their initial
aerobic capacity. Those with the lowest aerobic capacity have the
largest relative potential augmentation of maximal oxygen uptake (ml·min-1·kg-1)
(Shephard, 1997b). The gain in aerobic capacity is also dependant on the
training intensity, frequency and duration. Figure
1 presents the hypothetical dose-response curves for middle-aged
and elderly people. It has been suggested that among older individuals
both the beneficial and adverse effects of physical exercise may occur
with a lower dose of exercise than among younger individuals (Kallinen
and Alen, 1995; Shephard, 1997b).
General rules for exercise prescription for elderly people are complicated
to obtain because of great individual variation in fitness levels
and health. Most of the training studies have been performed among
elderly people less than 75 years old. Furthermore, most of these
studies have been done among men and healthy people. The general exercise
prescription differs in some aspects from that intended for younger
age groups. The exercise type should be chosen to cause minimal orthopaedic
stress among elderly people. If the effort tolerance of the elderly
individual is very limited, one longer exercise session should be
divided into several shorter bouts. Exercise duration in aerobic training
and repetitions in strength training are the first factors to be increased
before increasing training intensity among elderly people (ACSM,
2000).
Acute infection, recent myocardial damage, unstable coronary heart
disease or significant locomotor disturbances are standard absolute
contraindications to progressive exercise training programmes. Other
contraindications to progressive endurance or strength training are
presented in Table 8. Some warning
signs or symptoms, including angina or increased frequency of cardiac
arrhythmias (Table 9) in relation
to physical exertion, indicate that the exercise programme should
be stopped or that the exercise dose, usually intensity, should be
reduced.
|
SUMMARY OF THE LITERATURE |
According
to literature to date basic physiological factors and reduced muscle
mass are involved in the age-related decline in aerobic capacity and
effort tolerance among elderly people. A great proportion of the age-related
decline in physical performance is due reduced physical activity.
It is also clear that pathophysiological mechanisms (diseases) and
medications influence this decline and also the trainability of older
people. The physical capacity left over for managing everyday tasks
has been found to be higher in physically active persons than in sedentary
individuals in both cross-sectional and longitudinal studies. An appropriate
dose of exercise can reverse the age-related decline in physical performance
e.g. cardiovascular fitness. It is also apparent that the benefits
of exercise do not come without some short-term risks, especially
among persons not accustomed to regular physical exercise. It has
been suggested that both the beneficial and adverse effects of physical
exercise may occur with a lower dose of exercise among older than
younger individuals. The existing guidelines for exercise testing
and prescription have mostly been set for younger and middle-aged
people with only minor modifications for elderly and sick individuals.
Furthermore, the usefulness of exercise testing in the assessment
of risks prior to physical training and its prognostic value among
elderly people needs to be clarified.
Large beneficial effects of exercise training programmes have been
found among older people in both cross-sectional and longitudinal
studies. Most of these studies have, however, been performed among
apparently healthy elderly people. Additionally, these studies have
mostly been done among men aged less than 75 years. Data on effects
of exercise on elderly women aged 75 and over is especially scarce.
Thus, the over-all effects and safety of physical exercise among elderly
people with health problems are inconclusively documented in the scientific
literature. Few population-based randomised controlled studies have
been done to address general statements of the benefits and adverse
effects of physical exercise among elderly people.
|
AIMS OF THE STUDY |
To
address the issue of the overall beneficial or harmful responses
of physical exercise, the effects of physical exercise on cardiovascular
functions, fitness and health were examined among elderly people
in cross-sectional and longitudinal population-based studies. The
role of exercise testing was also clarified among elderly people.
The primary research objectives were the following:
1. To study the effect of physical activity level on cardiovascular
fitness and effort tolerance in elderly women in a cross-sectional
study.
2. To study whether exercise test status and exercise-test
results, including exercise capacity, are predictive for risk of
death in community-dwelling elderly men and women.
3. To study the beneficial and possible adverse effects of
an 18-week strength and endurance training programme on cardiovascular
functions, fitness and health among elderly women in a population-
based randomised controlled trial.
4.
To examine the acute and prolonged effect of acute exercise in the
form of a progressive cycle ergometer test on cardiac arrhythmias,
ST segment depressions and other cardiovascular adverse effects
in community-dwelling elderly people.
|
METHODS |
Effort tolerance in elderly people with different physical activity
backgrounds (Study 1)
Study design
Sixty physically active women (PA) aged 66-85 years were selected
from a sample of 600 members of Finnish sport organisations on the
basis of a physical activity questionnaire. Most of them had a life-long
training background and were still active in various sports (running,
cross-country skiing, track and field, gymnastics). As a control
group (CO) a random sample of 71 sedentary women aged 70-81 years
was taken from the population register of the rural municipality
of Jyväskylä. The control women performed light habitual physical
activities (housekeeping, shopping, walking). None of them, however,
reported regular endurance type training or other vigorous physical
exercise.
Fifty-two (87%) of the PA and 42 (59%) of the CO took part in the
laboratory examinations (Sipilä and Suominen, 1993). Those women who failed to attend the laboratory examinations
were interviewed by phone about the reasons to their non-participation
in the further examinations. Almost all of the control groups explained
their non-participation by reference to health problems, and the
physically active women failed to take part mostly because of travel
arrangements. The ethical committee of the Central Finland Central
Hospital approved the study protocol and all of the subjects gave
their written informed consent.
Laboratory
examinations
Before the laboratory investigations questionnaires were sent to
the subjects to elicit background data concerning their health,
medication, and physical activity. The laboratory examinations consisted
of various anthropometric and physiological measurements. A detailed
physical examination was done to establish he contraindications
for the exercise test (Table 10).
Blood pressure, body height and weight, body fat, and 12-lead ECG
were taken before the exercise. The bioelectrical impedance measurements
were performed at 10.00-10.30 h. The machine was calibrated daily
with standard resistor. Before the measurements the subjects had
fasted 3-4 h and not exercised for at least 12 hours. In our laboratory,
the coefficient of variation between two consecutive bioelectrical
impedance measurements has been in the order of 2-3%. In addition
erythrocyte sedimentation rate and blood hemoglobin concentration
were measured before the exercise. Serum gamma glutamyltransferace,
alanine aminotransferase activities, and creatinine concentration
were analysed afterwards to exclude hepatic or renal disturbances.
Cycle ergospirometry
Subjects were to perform an exhaustive cycle ergometer exercise
to their volitional maximum. The subjects were asked to keep the
pedalling frequency within the limits of 50-60 rpm as far as possible
and a weight of 200-300 g was added after every 2 minutes to the
cycle's basket connected to a mechanical braking system (Monark
814 E, Varberg, Sweden). The mean incremental loading after every
2 minutes was 18 W, depending on pedalling frequency.
The subjects were encouraged to continue pedalling the ergometer
to their personal maximum unless they experienced any exceptional
symptoms (chest pain, dizziness, severe breathlessness, musculoskeletal
pain). ECG leads II, V1, V5 and the well-being of the subject were
monitored continuously; 12-lead ECG, and brachial arterial cuff
pressure were recorded at minimum intervals of 2 minutes. Oxygen
uptake, carbon dioxide production, ventilation, and respiratory
exchange ratio (RER) were measured after each 30 seconds with a
gas analyser (Minjhardt Oxycon-4, Odijk, Holland). The indications
for exercise cessation were based on the guidelines of ACSM 1995
(Table 11).
The point of maximal effort was evaluated by the laboratory personnel
on the basis of objective signs of subject's exhaustion i.e. breathlessness,
or, if, for example, the pedalling frequency and work power consistently
decreased in spite of the subject's effort. On the other hand if
the exercise was terminated for medical criteria (Table
11) or if the subject suddenly stopped without having reached
exhaustion, the test was considered submaximal. According to their
ability to perform the exercise submaximally or maximally, the physically
active subjects and controls were divided into submaximally exercised
(submax.) and maximally exercised subjects (max.).
Analysis of plasma C-ANP and N-ANP
To evaluate the cardiac load a 10 ml blood sample from subject's
(sitting) cubital vein was taken by venapuncture in EDTA tubes immediately
before and within one minute after the ergometer test for the plasma
C-ANP and N-ANP analysis (Thibault et al., 1987). The subjects were highly co-operative and thus good
quality samples were obtained in all cases except in three cases
in which we failed to get a blood sample within a minute after the
exercise.
The blood samples were placed immediately in ice and centrifuged
within 60 minutes at +4 oC. Plasma was separated and
stored at -80 oC for further analysis. Plasma C-ANP and
N-ANP radioimmunoassays were carried out by using the methods described
previously (Vuolteenaho, 1985a; Vuolteenaho et al., 1985b; Vuolteenaho et al., 1992). For the C-ANP assay plasma samples were extracted with
Sep-Pak C18 cartridges (Waters, Milford, MA) with a recovery of
82 ± 10%. N-ANP was measured directly from 25 l plasma samples.
The sensitivities of the C-ANP and N-ANP assays were 2 pmol·l-1
plasma and 30 pmol·l-1 plasma, respectively. The intra-
and interassay coefficients of variation were < 10% and <
15%, respectively.
The two blood samples for C-ANP and N-ANP analysis were also taken
at 15-20 minute intervals from those subjects (n= 13) excluded from
the exercise to determine the normal variability of C-ANP and N-ANP
over time. N-ANP was measured in all of the 42 exercising PA and
in 19 out of the 22 exercising CO. The sample size of N-ANP was
reduced because of problems in the venapuncture of three subjects.
C-ANP was measured in 30 exercising PA and 16 exercising CO. The
marked reduction of 15 in the sample size of C-ANP was due to technical
problems (12 because of technical failure in the centrifuge thermostat
and 3 because of problems in performing the venapuncture).
Statistical analysis
All data were expressed as means ± SD. The difference between the
groups at the baseline was analyzed with one-way ANOVA. The effects
of physical loading on the response of C-ANP and N-ANP were assessed
using ANOVA with repeated measures. Pearson's product moment correlation
test was done to determine connections between C-ANP and N-ANP with
the physiological variables. Multiple linear regression analysis
was used to determine connections between aerobic capacity and the
other variables. Subjects with β- blocker were excluded for
all statistical analyses concerning heart rate and rate pressure
product (RPP) data. An alpha level of 0.05 was set to mark statistical
significance. The statistical software package used was SPSS for
windows version 6.0 (SPSS Inc., USA).
The predictive value of exercise testing for survival among 75-year-old
men and women (Study 2).
Study
design
The study population and the laboratory examination protocol are
presented in Figure 2. Complete
background, exercise test and mortality data were finally obtained
from 282 persons. The ethical committee of the University of Jyväskylä
approved the study protocol and all of the subjects signed a written
informed consent. About two weeks before attending the research
centre all the subjects were interviewed individually at home on
the subject of their health, current medication and living habits,
e.g. current smoking and physical activity.
Physical activity was assessed by the question "Which of the
following descriptions best corresponds to your current level of
physical activity?" The subject selected one of six alternatives
ranging from 1 (mostly light activities sitting in one place) to
6 (participating in competitive sports) (Grimby, 1986).
Subjects were divided into three categories according
to their physical activity level: category 1 (mostly light physical
activities or activities sitting in one place), category 2 (moderate
physical activities about 3 hours per week), category 3 (moderate
physical activities or sports at least 3 hours per week or heavy
physical activities at most 4 hours per week). Participation in
competitive sports was excluded from the categories as it did not
apply to any of the subjects. Physically inactive subjects were
considered to belong to category 1, intermediately physically active
to category 2, and physically very active to category 3. Current
smoking status was categorized as non-smoking, smoking occasionally,
or smoking daily.
At the research centre a standard physical examination was carried
out by a physician to check general health and medication prior
to the functional capacity tests. The number of chronic diseases
was calculated according to physicians' diagnoses of chronic conditions
lasted of over 3 months of duration. Blood pressure, body height
and weight, and 12-lead ECG were recorded before attempting the
cycle ergometer exercise. Body height and body mass were measured
using standard procedures. Body mass index (BMI) was calculated
as the relation of body mass (kg) to squared body height (m). In
addition, blood hemoglobin, and glucose concentration were measured
before the test. Hemoglobin A1c, total cholesterol and HDL-cholesterol
concentrations were analyzed from serum samples afterwards. The
contraindications for the cycle ergometer exercise were based on
the guidelines issued by the American College of Sports Medicine
1986(a non-exercise test group).
A progressive cycle ergometer exercise was administered to 74.0%
of the men and 66.0% of the women (77 men, 126 women). The indications
for terminating the cycle ergometer exercise were assessed by the
same physician (a specialist in sports medicine) on the basis of
the guidelines issued by the American College of Sports Medicine
1986 (Tables 10 and 11).
The Ethical Committee of the University of Jyväskylä approved the
study protocol and all of the subjects gave their written informed
consent to participation in the study.
Cycle
ergometer exercise
Subjects were to perform an exhaustive cycle ergometer test to their
volitional maximum pedalling at a frequency of 50 to 60 rpm for
as long as possible, and a weight of 300 or 600 g was added after
every 2 minutes to the a load basket which was connected to the
mechanical braking system of the ergometer (Monark 814E, Varberg,
Sweden). The amount of work achieved during each minute was then
calculated on the basis of the load and the actual number of revolutions,
the latter registered by a counter. The average initial load was
29 watts, and the average incremental load 18 or 36 W. Oxygen uptake
was not measured directly in this study.
The point of maximal effort was evaluated by the test personnel
on the basis of objective signs of the subject's exhaustion, e.g.,
breathlessness, or when pedalling frequency and work power fell
consistently in spite of the subject's efforts to maintain them
(exercise test completion group). On the other hand the test was
considered to have been prematurely terminated if the exercise was
stopped for medical reasons or if the subject suddenly stopped without
having reached exhaustion (exercise test termination group). All
the exercise tests were performed with the subjects on their current
medication. Thirty-seven percent of the subjects were taking nitrates
and 12% β- blockers. Digitalis and diuretics were being used
by 21% and 27%, respectively.
The number of the subjects in the non-exercise test group (NEX),
exercise test termination group (TER), and exercise test completion
group (CMP) are presented in Table
12. The proportion of subjects whose exercise test was prematurely
terminated was higher among men than among women (Table
12).
Analysis
of mortality
Time of death for all participants who died during the nine-year
follow-up was obtained from the official register of the province
of Central Finland and from hospital records. The principal causes
of death were classified and registered up until the year 1994 in
accordance with the 1977 International Classification of Diseases
(WHO, 1977) and thereafter in accordance with the 1992 International
Classification of Diseases (WHO, 1992). Mortality was followed up from the baseline studies
(1989 and 1990) until the end of 1998. Complete mortality data was
obtained for all the deceased subjects. The most frequent causes
of death were cardiac-related and ranged between 28 and 49% of cases
in the different groups. The figures of deaths from cancer ranged
between 12 and 36%.
Statistical analysis
Standard methods were used to calculate the means and standard deviations
of the variables. Students t- test (two-tailed) or analysis of variance
(ANOVA, Least Significance Difference test, LSD- test) were used
in comparisons of means for continuous variables. Contingence tables
and χ2-test were used to compare categorical data.
Survival distributions were analyzed by using statistics D (Lee
and Desu, 1972) for the non- exercise test group, exercise test termination
group, and exercise test completion group. The Cox proportional
hazards model (Cox, 1972)
was used to estimate the relative risk for mortality
in terms of exercise-test status, sex, various physical characteristics,
health status, physical activity, and physical performance. Subjects
who did not die during the follow-up were assigned a survival time
of 9 years. For those who died during the follow-up, survival time
was calculated as the time from the beginning of the study to the
day they died.
Three main models were created to calculate the hazard ratios for
death: Model 1 with unadjusted hazards ratios for all three study
groups, Model 2 with adjusted hazards ratios for all three study
groups, and Model 3 with adjusted hazards ratios for the exercise
test completion group. The adjusted models were controlled by sex,
number of chronic diseases, physical activity level, and, additionally
in the exercise test completion group, cycling power. The adjustment
was done step by step by adding one factor after another into the
new model. The covariates included in the models were selected on
the basis of their known or suspected association with mortality.
Covariates not having a significant association with mortality were
excluded from the main three final models presented in the results.
The excluded covariates were BMI, smoking, blood hemoglobin, blood
glucose, hemoglobin A1c concentrations, total cholesterol and HDL-cholesterol
ratio. Cumulative models were created to calculate the hazard ratios
between three groups: two sub-groups of the exercise test termination
group, i.e., termination for cardiovascular reasons, and termination
for other reasons, and an exercise test non-termination group.
The computations were done with SPSS 10.0 software (SPSS Inc., Chicago,
IL).
Improving cardiovascular fitness by endurance and strength training
(Study 3)
Study
design
A postal questionnaire about health, medication, physical activity
level, and functional status was send to a random sample of 76-
to 78-year-old women (n= 240) drawn from the population register
of the city of Jyväskylä, Finland. Of the 157 women (65.4%) who
responded to the questionnaire, 65 women reported no severe diseases
or functional impairments which could exclude their performing the
cycle ergometer test and the subsequent strength or endurance exercise
programme on the basis of a physician's evaluation and the guidelines
for exercise testing and prescription issued by ACSM (Table
10).
Fifty-four women participated in the laboratory examinations. The
remaining 11 who did not attend the laboratory examinations explained
their non-participation by lack of time, travelling, and poor health.
Forty-two women with no contraindications for physical exercise
were randomly assigned to strength (n= 16), endurance (n= 15), and
control (n= 11) groups. The randomisation was performed manually
by drawing lots after deciding the number of subjects in each group.
The number of subjects in the two exercise groups was intentionally
larger than that in the control group to overcome the possible higher
drop-out in the exercise groups. Some of the subjects had chronic
conditions (Table 13) which,
however, did not exclude them from physical training. Nine subjects
had no prescribed medications, 13 subjects had a nitrate as medication,
9 subjects had a ß- blocker, and 6 subjects used calcium channel-
blockers respectively. Only one person used digitalis. The level
of physical activity in all of the groups studied averaged 3 in
six class scale (Table 13),
i. e. around 3 hours moderate physical activity per week, involving
domestic tasks such as cooking, cleaning, straightening up the room,
making beds, and ordinary gardening, walking longer distances, and
cycling. None of the subjects reported regular vigorous physical
exercise.
Twelve subjects in the exercise groups and eleven in the control
group completed the intervention. Of the seven women who withdrew
from the study, six stopped because of illness and one was unwilling
to continue. The study was approved by the ethical committees of
the Central Finland Central Hospital and of the University of Jyväskylä.
A written informed consent was received from all the subjects.
Laboratory examinations
Body height and body mass were measured using standard procedures.
Lean body mass (LBM), and body fat were assessed by bioelectrical
impedance (Spectrum II, RJL Systems, Detroit, MI). Maximal isometric
force was measured in a sitting position on a custom-made dynamometer
(Sipilä et al., 1996).
A clinical examination, blood tests (glucose, haemoglobin, erythrocyte
sedimentation rate), right brachial arterial cuff pressure after
10 minutes' rest, resting and exercise ECG preceded the exercise
capacity tests to set the contraindications for exercise (Table
10).
Cycle ergospirometry
The subjects performed a symptom-limited cycle ergometer exercise
to their volitional maximum according to the protocol described
in the methods section of study 1. Oxygen consumption, carbon dioxide
production, ventilation and respiratory exchange ratio were assessed
by a gas analyser (Minjhardt Oxycon-4, Odijk, The Netherlands).
The cycle ergometer and the exercise test were done at the baseline
and after the 18-week intervention in all subjects. The strength
measurements were additionally performed after 9 weeks of the intervention.
Physical training
Both exercise groups participated in an 18-week progressive physical
training program which consisted of a 2-week orientation phase and
a 16-week training phase. The subjects had supervised 1-hour training
sessions twice a week during the orientation phase and three times
a week during the training phase. At the beginning of each training
session, both groups had a warm-up period of 10 minutes, including
brisk walking and stretching. At the end of the session, stretching
exercises for the major muscle groups were performed. The subjects
in strength and endurance groups participated in 85-95% of the exercise
sessions.
Strength group trained the major muscle groups (muscles of the thigh,
calf and trunk) on equipment using compressed air as a resistance
(HUR, Kokkola, Finland). The intensity of the training was gradually
increased from 60% (first 3 weeks) of the 1 RM (repetition maximum)
to 75% of the 1 RM (last 4 weeks). 1 RM was defined as the heaviest
load the subject could move in acceptable way throughout the complete
range of motion. The resistance was individually adjusted according
to the one-repetition maximum test (1 RM) measured at 2-wk intervals.
To obtain the 1 RM, the initial resistance was set close to the
previous 1 RM result. The resistance increment was 0.25 bar, which
corresponded to 2.5 kg in knee flexion, 3 kg in the knee extension
and 5kg in the combined knee-hip extension.
After the 18-week training period, the 1RM values increased on the
average 19 - 60 % depending on the muscle group tested. The individual
variation between the two final 1 RM measurements averaged 2%. During
the strength training sessions the subjects performed three to four
sets of 8-10 repetitions with a 30-s pause between sets. Each repetition
lasted for 4-6 s, with no more than 2 s rest between the repetitions.
The endurance group walked on an indoor track twice a week and had
step aerobics once a week. The training heart rate was individually
adjusted on the basis of the initial cycle ergometer test. The training
intensity was gradually increased from 50% (first 5 weeks) to 80%
(last 4 weeks) of the initial heart rate reserve. The training heart
rates were controlled by heart rate monitors (Sport Tester, Polar
Electro, Kempele, Finland) during the training sessions. The walking
session lasted 20 min in the first 2 weeks and 30 min in the subsequent
16 weeks. The walking distance during indoor walking increased from
the average value of 1500 m (range 1200-2200 m) to the 2700m (range
2400-3300 m) in the end of the training period. The step-aerobics
session lasted for 40 min, during stepping on a bench 0.10 m or
0.15 m in height.
Controls were instructed to continue their habitual physical activity
levels. All subjects, including the subjects in the control group
kept a diary concerning their physical activities during the intervention
to detect possible changes in physical activity level. A routine
clinical examination was repeated after 9 and 18 weeks of the intervention
to all subjects. Any new symptom was examined by the supervising
physician and the training stopped if necessary.
Brachial arterial cuff pressure was measured before exercise sessions.
Ambulatory ECG was registered in 3 subjects in the training groups
because of chest pains in order to exclude possible cardiac disease
or dysfunction behind the symptoms.
Statistical
analysis
Standard statistical procedures were performed to calculate means
and standard errors (SE). The differences between the groups at
the baseline were analysed using either the one-way ANOVA or chi-square
test. The effects of training were assessed using two-way ANOVA
with repeated measures. An alpha level of 0.05 marked statistical
significance in the group comparisons for independent samples. If
the significance of the interaction of group by time in ANOVA with
repeated measures was p < 0.10, the training effect was localised
utilising simple contrasts with a p < 0.05. The statistical power
of detecting a significant interaction was 0.614 for peak power
(W·kg-1) and 0.238 for peak oxygen uptake (ml·kg-1·kg-1).
The statistical software package used was Sigma Stat program version
2.0 (Jandel Scientific Corp, USA) or SPSS for windows (SPSS Inc.,
Cary, NC).
Cardiac adverse effects and acute exercise (Study 4)
Study
design
The general design of the study is presented in Figure
3. The study population was the same as in study 2. The target
population consisted of all 75-year-old residents of the city of
Jyväskylä, Central Finland (n= 388). Of them 295 (76%) entered the
laboratory for the assessment of their health and functional capacity
(Heikkinen, 1997). Before entering the laboratory all of them were interviewed
individually at home about their background data of health, functional
capacity and living conditions. A questionnaire of health and physical
activity was given to t he subjects to fulfil before entering to
the laboratory examinations. Physical activity was assessed with
the question "Which of the following descriptions best corresponds
to your current level of physical activity?" The subject selected
one of 6 multiple-choice alternatives (Grimby, 1986).
A detailed physical examination was done in the laboratory by a
physician to check general health and medication prior to the functional
capacity tests. Blood pressure, body height and weight, body fat
(by bioelectrical impedance, Spectrum II, RJL Systems, Detroit,
MI), and 12-lead ECG were recorded before cycle ergometer exercise.
In addition, the erythrocyte sedimentation rate, blood haemoglobin
and glucose concentration were measured before the exercise. Total
cholesterol and HDL-cholesterol concentrations were analysed from
serum samples afterwards. The contraindications for cycle ergometer
exercise were based on the guidelines issued by ACSM 1986 (Table
10).
A progressive cycle ergometer exercise was then administered to
74.0% of the men and 66.0% of the women (77 men, 126 women) (population
group, PG). The indications for terminating the cycle ergometer
exercise were assessed by the same physician (a specialist in sports
and exercise medicine) on the basis of the guidelines issued by
ACSM 1986 (Table 11). Maximal
isometric strength measurements, 10-meter walking test, and stair-mounting
test were performed by the subjects on the same day as the cycle
ergometer exercise. Additionally, some psychological tests were
administered in the intervals between the physical capacity tests.
The subjects stayed in the laboratory for the assessments for an
average of 6 hours on the same day.
Any possible contact by the subjects with the central hospital,
to which all acute cardiac cases are referred, during the 24-hour
period after the laboratory examinations was to be obtained from
the hospital's patient records. Thirty-six subjects out of the PG
were invited to the ambulatory ECG recordings and the second cycle
ergometer exercise on the basis of the prior clinical examination,
laboratory tests (blood hemoglobin and glucose, ECG) and initial
exercise test on the cycle ergometer. Of this number 28 subjects
(16 women and 12 men) with no contraindications to heavy physical
exercise participated in the second cycle ergometer exercise and
ambulatory ECG recordings (holter group, HG).
The primary inclusion criterion for the subjects in the HG group
was that they were able to attain their peak physical effort in
the initial cycle ergometer test. The second criterion was that
the subjects should not have had any regular medications influencing
on the amount of heart arrhythmia and ST segment changes. Thus,
the subjects of the HG were free of any observable limitations on
physical loading and were apparently healthy and asymptomatic of
cardiovascular diseases. One person, however, had previously suffered
myocardial infarction and one had mild bronchial asthma and medicated
hypothyreosis.
The ethical committee of the University of Jyväskylä approved the
study protocol and all of the subjects signed a written informed
consent.
Cycle ergometer exercise
The subjects (both in PG and HG) were to perform an exhaustive cycle
ergometer exercise to their volitional maximum, as described in
the methods section in study 2. All the exercise tests were performed
with the subjects under their current medications. Thirty-seven
per cent of the subjects were taking nitrates and 12% β-blockers.
Digitalis and diuretics were being used by 21% and 27%, respectively.
Ambulatory ECG
Ambulatory ECG recordings were taken 24 hours before and after the
cycle ergometry (HG). Portable two-channel tape recorders (Marquette
Electronics Inc., USA) were used with electrode placement to obtain
modified V1 and V5 leads. Before final electrode
placement the height of the calibration signal and R-signal were
checked (minimum 10 mm in the modified V5) and the electrodes
were replaced if necessary.
The recorders were applied between the hours 8-11 a.m. and were
removed at the same time the following day. The subjects went home
wearing the recorder on a waist belt and continued with their normal
daily activities. They were asked to maintain the daily activities
performed over the two consecutive 24-hour periods comparable. The
subjects kept a diary of their activities and symptoms. They were
also asked to push the 'event' button of the holter device if they
had any exceptional symptoms, i.e. severe breathlessness, dizziness,
feelings of arrhythmia or chest pains.
The ECG tapes were analyzed in the routine scanning mode with a
Marquette Laser Holter (Marquette Electronics Inc., USA) electrocardioscanner
by the same technician. The number of ventricular premature beats
(isolated, couplets, runs), supraventricular beats (isolated, runs)
and ST segment depressions were compared between the two consecutive
time-matched recordings before and after the maximal exercise. Rhythm
strips were obtained to document the complexity of arrhythmia and
the nature of each ST segment depression.
The criteria for calculating ST segment depressions were as follows:
every ST segment depression was checked and registered if it was
> 1.0 mm from the baseline at 60 milliseconds after the
J-point and lasted at least 1.0 minute. There should also be an
interval of at least 2 minutes between two separate ST segment depressions.
In relative ST segment depressions the basal time constant was 2
hours. Slowly ascending, horizontal or downsloping ST segment depressions
were taken into account for comparison. The recordings of 5 subjects
were excluded from the data analysis, two because of poor quality
of the ECG signal in the ambulatory ECG recordings, one because
of incomplete exercise data, one because of left bundle branch block,
and one because of β-blocker medication. Altogether the ambulatory
recordings of 12 men and 11 women were available for the statistical
analysis.
Statistical
analysis
Standard statistical procedures were performed to calculate means
and standard errors (SE). The differences between the men and women
in the PG and HG were analysed doing T-test, Mann- Whitney Rank
Sum test or Chi-Square test. The effects of physical loading on
cardiac arrhythmia and ST segment depressions among both sexes were
assessed using two-way ANOVA with repeated measures. An alpha level
of 0.05 was set to mark statistical significance. The statistical
software package used was SigmaStat program version 2.0 (Jandel
Scientific Corp, USA).
|
RESULTS |
Effort tolerance in elderly people with different physical activity
backgrounds (Study 1)
Background
data
The exercised physically active women (PA) and control women (CO)
were comparable in age. PA were leaner than CO (Table
14). Submaximally exercised PA were somewhat older than maximally
exercised PA. Cardiovascular and musculoskeletal problems were common
in the groups studied especially among CO in submax. group (Table
15). Three of the exercised controls used digitalis medication
and 4 used beta-blocker. Among the physically active elderly women
4 used digitalis and 2 used beta-blocker, respectively.
Cycle ergospirometry and aerobic capacity
Twenty-two of the 42 PA terminated the ergometer exercise before
objective exhaustion, and of the CO only 3 out of the 22 went to
the maximum. The most common reasons for termination among PA were
the subject's own wish to stop or abnormal cardiovascular reactions.
Among CO tiredness of the legs was also a common reason for termination
(Table 16). In submaximal
exercise PA differed from CO in aerobic performance characteristics
only when expressed in relation to body weight. In maximal exercise
the difference in peak heart rate and rate pressure product (peak
RPP) reached statistical significance (Table
17).
Aerobic capacity expressed in peak power and peak oxygen uptake
was higher among PA than CO.
This difference was more pronounced when the aerobic capacity figures
were expressed in relation to body weight. The RER values tended
to be lower among CO than PA (Table
17).
Assessment
of cardiac load during exercise by C-ANP and N-ANP
Both C-ANP and N-ANP increased during physical loading in submaximal
and maximal exercise (Figure 4a
and Figure 4b). No significant
differences between the groups were found in the effect of exercise
on either C-ANP or N-ANP (ANOVA with repeated measures). The basal
level of N-ANP among PA before submaximal exercise was, however,
significantly higher than before maximal exercise among PA and higher
than before submaximal exercise among CO (Figure
4a and Figure 4b).
Exercise
test outcome and mortality (Study 2)
The survival of the subjects
Of the 282 subjects, 117 (42%) died during the 9-year follow-up.
In the non-exercise test group 49 subjects (62%) died, in the exercise
test termination group 32 (34%) and in the exercise test completion
group 36 (33%). The most frequent causes of death were cardiac-related
and ranged between 28 and 49% of cases in the different groups.
The figures of deaths from cancer ranged between 12 and 36%. The
non-exercise test group had significantly higher mortality than
the exercise test termination group. A similar difference was found
between the non-exercise test group and exercise test completion
group. No statistically significant difference was found in survival
between the exercise test termination group and exercise test completion
group either over the whole 9-year follow-up or after 4, 5, and
6 years of observation.
Cox
proportional hazards models for mortality
The multivariate hazard ratio (HR) for death was 1.87 times higher
among the subjects in the non-exercise test group than in exercise
test completion group. A similar difference was found between the
non-exercise test group and exercise test termination group (HR
1.97, CI 1.24 - 3.13). No statistically significant difference was
found in the risk for death between the exercise test completion
group and exercise test termination group.
The high peak cycling power in W·kg-1 body weight was
associated with reduced risk for death in Model 3 (multivariate
HR 0.20; CI 0.08 - 0.50). In both models a high number of chronic
diseases per subject was independently associated with an increased
risk for death. Males were at increased risk for death in Model
3. Physical inactivity was independently associated with increased
risk for death in Model 2. In this model the risk for death in relation
to physical inactivity was defined as risk for death among the physically
inactive subjects (category 1) compared to physically very active
subjects (category 3). The risk for death among the intermediately
physically active subjects (category 2) compared to risk for death
among the physically inactive subjects (category 1) did not reach
statistical significance.
The hazard ratio for death among subjects whose tests were terminated
for cardiovascular reasons was 1.185 (CI 0.71 - 1.99) compared to
the exercise test completion group in a non-adjusted model (data
not shown). When both gender and cycling power were controlled the
corresponding hazards ratio was 0.78 (CI 0.45 - 1.36). In the latter
model male gender resulted in a hazard ratio of 2.33 (CI 1.36 -
3.98) and cycling power in W/kg of 0.31 (CI 0.17 - 0.55).
Improving cardiovascular fitness by endurance and strength training
(Study 3)
Background
data
The medications, health characteristics, and physical activity level
of the subjects at the baseline are presented in Table
13. No significant differences were found in these variables
or in the baseline values of physical characteristics between the
groups. Beyond the training induced in the trial, the study groups
did not differ with respect to the initial level of physical activity,
which remained constant throughout the experiment. Body fat decreased
significantly among the subjects in the strength training group
compared to the controls (Table
18).
Effects
of training on aerobic capacity
There was a significant increase in peak power in Watts (W) in the
strength training compared to control group (Table
19). Peak power in Watts·kilogram-1 body weight increased
in both the endurance and strength training groups compared to controls.
No interaction of group by time was found for peak oxygen uptake
(Table 19). The respiratory
exchange ratio (peak) did not differ between the baseline and after
the 18-week intervention in any of the groups (Table
19). The mean percentage changes in peak oxygen uptake (ml·kg-1·min-1)
in the endurance, strength, and control groups, respectively, were
+6.8 %, +9.4 %, -6.2 %.
The mean respective percentage changes in power (in W·kg-1)
were +3.8 %, +8.1 %, and -5.9 %. There was wide inter-individual
variation in all groups in percentage change in peak power and peak
oxygen uptake (Figure 5a and
Figure 5b).
Health
problems emerged during the exercise intervention
Six subjects (19%) in the exercise groups withdrew from the study
because of health problems. One subject in the endurance group dropped
out of the intervention because she was unwilling to continue. Two
subjects in the exercise groups were not able to the intervention
in the exercise groups.
One subject in the strength group died because of large myocardial
infarction 8 weeks into the intervention. The symptoms of the myocardial
infarction started two days after the exercise session. No cardiac
problems, or hospital contacts because of heart problems before
the intervention were documented. The initial exercise ECG showed
no cardiac ischemia. Another subject in the strength group sustained
an unstable angina pectoris at 4 weeks into the intervention starting
2 days after the exercise session. She was operated successfully
for three- vessel coronary heart disease. In her medical history
she had been treated in the hospital 2 years before the exercise
intervention for a chest pain attack, but this event was considered
non-cardiac. A small painless and horizontal 1mm ST segment depression
in leads V5 and V6 was detected in her initial
exercise ECG at peak exercise.
One person in the strength group began to suffer from occasional
angina pectoris and dyspnoe when walking at 8 weeks into the intervention.
No actual ST segment changes were seen in her resting ECG and the
chest X-ray was normal. ST segment depressions were detected in
her initial exercise ECG neither. A nitrate was prescribed for evident
angina pectoris and the symptoms disappeared. Her exercise intervention
was terminated.
A member of the endurance group had slight weakness of the limbs
in the right side together with mild dysartria 2-3 hours after the
strength measurements at 9 weeks into the intervention. A neurologist
made a clinical diagnosis of infarction of the brainstem. The symptoms
gradually disappeared. Her exercise intervention was terminated.
In the last medical screening (after the 18 weeks endurance training)
a suspected abdominal aortic aneurysm was found in one asymptomatic
woman. An abdominal aortic aneurysm with diameter of 5 cm was confirmed
by ultrasonography. The subject was excluded from the final measurements
and she was successfully operated after the intervention.
Six cases of musculoskeletal problems emerged in the exercise groups,
but these complaints were minor and did not lead to premature termination
of the exercise intervention. One subject in the strength group,
however, fractured her clavicle when she fell off a bicycle during
her free-time.
Cardiac
adverse effects and acute exercise (Study 4)
Cardiac disturbances during cycle ergometer test and cardiac adverse
events after the test
In the population group (PG) the cycle ergometer exercise (CEE)
was terminated in 23.4% of the men and 6.4% of the women because
of cardiac arrhythmia or deep ST segment depression (gender difference,
χ2 = 10.93, p < 0.001). Almost twelve percent
(11.7%) of the men were stopped because of deep ST segment depression
compared to 5.6% of the women (gender difference, χ2
= 1.70, p = 0.192). An increasing number of ventricular premature
beats or multifocal ventricular premature beats was the reason for
exercise cessation in 6.5 and 5.2% (men) and 0.8 and 0.8% (women)
of the subjects (gender difference for the arrhythmia, χ2
= 9.90, p= 0.002). No episodes of nonsustained ventricular tachycardia
were detected in our subjects. One subject in the PG was referred
to hospital immediately after the cycle ergometer exercise because
of acute atrial fibrillation while performing it. The subject was
treated successfully in the local hospital.
No other subject in the PG was referred to hospital within the 24
hours following the laboratory examinations. Seven performances
(3 men and 4 women) out of 23 in the HG were submaximal. Five out
of these seven were terminated for medical reasons, 3 cases because
of deep ST segment depression and 2 because of bundle branch block.
Cardiac
disturbances in the 24-hour ambulatory ECG recordings
As expected, the sum duration of the ambulatory ECG recordings was
similar in time-matched pre-exercise and post-exercise periods in
both the men and the women (holter goup, HG). Similarly, no gender
differences were found in the minimal, average or maximal heart
rates.
The men had a lower mean number of isolated ventricular premature
beats in the post-exercise than pre-exercise period, whereas among
the women the opposite was true (HG). However, the effect of exercise
on isolated ventricular premature beats (p = 0.309) and isolated
supraventricular premature beats (p = 0.251) did not differ significantly
between the sexes in the HG.
Also, there were no statistically significant intragroup differences
in isolated ventricular beats between the pre- and post-exercise
recording periods among either in men (p = 0.665) or in women (p=
0.555) in the HG (Figure 6a).
The same was true in isolated supraventricular premature beats (p
= 0.795 and p = 0.896) respectively (Figure
6b). A corresponding result was found with the number of ventricular
couplets, runs, and supraventricular runs, respectively (data not
shown). Ventricular runs occurred in 2 men and 2 women having 1-5
episodes of ventricular runs with 3-5 consecutive beats at a rate
of 121-147 beats per minute.
Totally of forty-five ST segment depressions (range -1.0 - - 7.1mm
and 1.10- 41.50 minutes) meeting the criteria mentioned earlier
were found among three men and four women in the HG during the two
recordings. No angina pectoris was reported in relation to these
ST segment depressions. The number of ST segment depressions was
comparable between these two recordings, with 24 in the pre-exercise
and 21 in the post-exercise period. In four subjects (three women
and one man) the number of depressions, however, increased in the
post-exercise period. In two subjects the number of ST segment depressions
decreased (one woman and one man) in the post-exercise period and
remained the same in one subject (a man).
Exercise had no significant effect in either gender on the variables
related to ST segment depressions (Table
20). Men in the HG showed significantly
more severe ST segment depressions than women as expressed in peak
absolute ST depressions and ST-deviation time. Men tended also to
have longer periods of ST segment depressions than women. There
also was a tendency among men and women to have deeper ST segment
depressions during the pre-exercise period than the post-exercise
period (Table 20).
When looking at the time period surrounding the acute physical exercise
(from 0,1, 2 hours pre-and post-exercise) the number of isolated
ventricular premature beats increased considerably in relation to
exercise in 5 cases in the men and in 4 cases among the women in
the HG (data not shown). The number of isolated supraventricular
premature beats increased in 6 cases among the men and 1 case among
the women. Furthermore, the ST-deviation time was more pronounced
in 7 cases among the men during the observation period (0, 1, 2
hours pre and post-exercise); a similar effect was seen in 2 cases
among the women (data not shown).
In general, the cases of more marked arrhythmia and ST segment depressions
occurred usually in the exercise hour, and during the pre- or post-exercise
hour in both men and women. According to the two-way ANOVA, no significant
gender differences were found in the HG in the effect of exercise
on these variables. Differences in these variables between the recording
hours and sexes did not reach statistical significance either.
DISCUSSION |
It
has been suggested that both beneficial and harmful effects
result at a lower dose of exercise among elderly people than
among younger people (Kallinen and Alen, 1995).
The existing recommendations with respect to exercise doses
differ between older and younger people, however, rather little
(ACSM, 1998;
2000).
Most of the former studies have found exercise to have substantial
beneficial effects among selected groups of elderly people.
In the present research the beneficial effect of physical
exercise on cardiovascular fitness and effort tolerance was
studied first, and the cardiovascular fitness among physically
active women compared to that among less active sedentary
women in a cross-sectional study. Secondly, the beneficial
effect of an 18-week endurance and strength training programme
on cardiovascular fitness was further studied among women
aged 76 to 78 years in a population based randomized controlled
trial. Possible harmful effects of physical loading were evaluated
in relation to acute exercise in the form of a cycle ergometer
test and in relation to 18-week endurance and strength training
programmes. Furthermore, the value of exercise testing among
community-dwelling elderly people was clarified.
Cardiovascular benefits of exercise
Cardiovascular
fitness and effort tolerance among physically active women
and less active control women (Study 1)
Physically active women had superior aerobic performance and
effort tolerance compared to the less active control women
(study 1). The physically active women had a peak oxygen uptake
(in ml·kg-1·min-1) 25 and 40% higher
than that of the control women in the submaximal and maximal
cycle ergometer exercise tests. Forty-eight percent of the
physically active women reached the objective maximum in the
exercise test. The corresponding proportion in the less active
control women was only 15%. In the large meta-analysis by
Fitzgerald et al. (1997) and Wilson and Tanaka (2000) a comparable difference in aerobic capacity between physically
active and sedentary subjects aged 18 to 89 years was found.
Sixty-three and 75 percent higher aerobic capacity was, however,
reported in the endurance trained men and women aged 18 to
89 years compared to sedentary controls (Fitzgerald et al.,
1997; Wilson and Tanaka, 2000).
In the two meta-analysis (Fitzgerald et al., 1997; Wilson and Tanaka, 2000) physically active persons were defined as those who participated
in occasional or irregular (< 2 times per week)
performance of aerobic exercise (walking, basketball, dancing,
stairmaster exercise, etc.). Sedentary subjects were defined
as performing no aerobic exercise. Endurance-trained persons
regularly performed vigorous endurance exercise (e.g. running,
cycling, cross-country skiing) > 3 sessions·wk-1
for > 1 yr. Most of the physically active subjects
in study 1 had a life-long physical training background and
were still active in various sports (running, cross-country
skiing, track and field, gymnastics). Additionally, a weighed
sum of the annual training kilometres (walking, running, cross-country
skiing, swimming, cycling) of the physically active persons
was 2.7 times of the less active control women. The control
women in study 1 performed only light physical activities
(housekeeping, shopping, walking) and none of them reported
regular endurance-type training or other vigorous physical
exercise. The control women in study 1 were, however, not
totally sedentary because of this physical activity during
the activities in their daily living. The differences in defining
the physical activity level make the comparisons of the magnitudes
of the effect of physical exercise on aerobic capacity between
the studies difficult. Nevertheless, physical exercise was
found to have a marked beneficial effect on cardiovascular
fitness in all age-groups in these cross-sectional studies.
In the meta-analyses by Wilson and Tanaka, 2000 age explained 65 to 75% of the total variance in the reduction
in aerobic capacity. Body mass explained an additional 3 to
10% of the variance. In the two meta-analyses (Fitzgerald
et al., 1997; Wilson and Tanaka, 2000) training dose (running mileage) was inversely associated
with age in both men and women. This suggests a significant
decrease in training dose with advancing age. However, the
number of the subjects aged 70 years and over was limited
in both meta-analyses and the associations between age, body
mass, training kilometres and cardiovascular fitness in elderly
people remained rather obscure. In study 1 among the women
aged 66-85 years, age correlated negatively with cardiovascular
fitness only in the physically active women, but no association
between lean body mass and cardiovascular fitness was found.
There was neither a significant association between age and
physical activity (in kilometres) among the physically active
women. Among the control women no association emerged between
age and cardiovascular fitness. Lower lean body mass did not
explain the higher peak oxygen uptake per body weight (ml·kg-1·min-1)
among the physically active women as the absolute values (l·min-1)
were also higher. It is suggested that the higher peak oxygen
uptake in physically active women was due to their higher
level of physical activity. However, the analysis concerning
the associations between age, lean body mass, physical activity,
and aerobic capacity suffer from a limited number of subjects
and relatively narrow age range in study 1.
Chronic diseases and medication can also influence cardiovascular
fitness and effort tolerance (see introduction). In study
1 the control women had twice as many diseases as the physically
active women. It is evident that the higher prevalence of
cardiovascular diseases among the control women than among
their physically active age-peers had an impact on the difference
in cardiovascular fitness between these two groups. The prevalence
of musculoskeletal disorders was higher in the control than
in the physically active women. Musculoskeletal problems may
hamper the function of the lower extremities and thus be a
limiting factor in a cycle ergometer test. The cycle ergometer
test was used in these studies because it allows better control
of movement and balance together with more precise monitoring
of ECG and blood pressure. No difference in the respiratory
exchange values between the physically active and control
women was found. Also, the cardiac load assessed by N-and
C-ANP increase during the exercise tests was comparable between
the study groups. The cardiovascular and metabolic demand
was thus comparable between the study groups during the cycle
ergometric loading.
The results of cross-sectional studies usually suffer from
selection bias. The most fit and healthy physically active
persons are likely to continue their training into the later
years of life. Those who get sick usually stop their training
or decrease their level of physical activity. Thus cross-sectional
comparisons between physically active persons and less active
persons may, because of this selection bias, overestimate
the benefits of physical training. Rogers et al. (1990)
found, however, in their longitudinal study with a mean follow-up
of 8 years one-half the rate of decline in aerobic capacity
among those master athletes (mean age 62 years) engaged in
regular vigorous endurance exercise than that prevalent among
age-matched sedentary subjects.
High exercise capacity as a protective factor for survival
(Study 2)
In study 2 peak cycling power (in W·kg-1 body weight)
was a strong and independent predictor of death. In the non-adjusted
models (not shown in the results) an increase in cycling power
of one W·kg-1 decreased the risk for death by 97%
during the 9-year period. 0.2 W·kg-1 cycling power
is approximately equivalent to one MET (oxygen uptake 3.5
ml·kg-1·min-1 at rest). An increase
in cycling power of 0.2 W/kg (approx. one MET) corresponded
a 19% decrease in mortality risk. In the study by Goraya et
al. (2000) an increase of 1 MET in maximal workload in a treadmill
exercise test was associated with an 18% reduction in the
risk for death among elderly persons. The decrease in the
risk for death for every increase of 1 MET in exercise capacity
was almost the same in younger persons (Goraya et al., 2000). Gulati et al. (2003) found a 17% reduction in the risk for death for every
1 MET increase in treadmill exercise capacity among middle
aged women.
The magnitude of the association between high exercise capacity
and low mortality found in this study conducted among elderly
people is well in line with that reported in the scientific
literature (Goraya et al., 2000; Gulati et al., 2003). Both men and women seem to benefit from this reduction
in risk. In the study by Era et al. (2001) maximal cycling power in an ergometer test was associated
with risk for death among 70-year-old men but not among women.
Messinger-Rapport et al. (2003) reported that heart rate recovery and exercise capacity
independently predicted mortality not only in older patients
in general, but also in those aged 75 and older and among
both sexes.
The association of physical activity and exercise capacity
with mortality in elderly people can be explained in several
ways. First, physical activity and fitness are closely related
to each other. People with a latent or prevalent disease are
evidently more passive as well as less fit than their healthier
counterparts and thus more prone to die. The reason for this
association could therefore arise from the selectivity of
the study subjects rather than from the causal relationship
between physical activity and physical performance and mortality.
The protective effect of physical activity and exercise capacity
on the progression of disease, and thus on premature death,
could be another explanation for this association. Most of
this protection is assumed to result from the beneficial effects
of physical exercise on blood lipids, blood pressure, glucose
metabolism, vascular function, autonomic tone, blood coagulation,
and inflammation (Balady, 2002). This assumption is supported by research findings
which show that among middle-aged and older men less fit and
less active persons can improve their prognosis by increasing
their level of physical activity or fitness (Dorn et al.,
1999; Paffenbarger et al., 1995).
A consistent dose-response relationship between physical activity
and mortality was not found. There was no difference in mortality
between the physically very active and intermediately active
subjects. Neither was there a significant difference in mortality
between the intermediately and inactive subjects (not shown
in the results). This may be due to our way of assessing the
amount of physical activity, which may not be accurate enough.
It is also possible that a certain exercise threshold is needed
before the beneficial effects of exercise on mortality become
evident.
Effects
of endurance and strength training on cardiovascular fitness
(Study 3)
Substantial and beneficial gains in cardiovascular fitness
have been reported in most of the training studies conducted
among elderly people. An increase in aerobic capacity of up
to 38% with endurance exercise training has been reported
among older people (Shephard, 1997b) depending on baseline aerobic capacity, exercise duration
and frequency, and training modality. However, Benestad (1965) found no increase in VO2max in elderly subjects
following endurance training for 6 weeks. In this study the
duration of the training bouts was less than 15 minutes and
the subjects trained three times per week. Sidney and Shephard
(1978) found a decrease in VO2max following low-intensity
and low frequency training. Other studies have also reported
low gains in VO2max following endurance exercise
training among elderly people (DeVries, 1970; Foster et al., 1989).
Most of the former studies showing a substantial increase
in VO2max following endurance training have been
conducted among selected samples of healthy elderly people,
mostly among men under 75 years of age. The gain of 6.8% in
cardiovascular fitness from endurance training found in study
3 is among the lowest reported. Study 3 was a randomised controlled
trial carried out among elderly subjects age 76 to 78 years
and with health problems. Considerable variation in individual
gains in cardiovascular fitness was also found (Figure
5b). Kohrt et al. (1991) reported a mean increase of 26 (men) and 23% (women)
in VO2max with a range from 0 to 58% following
9-12 months endurance training among elderly persons aged
60 to 71 years. Age was not significantly associated with
the gain of aerobic capacity in their study as the age range
of the subjects was limited. In the meta-analysis by Green
and Crouse (1995)
both pretraining VO2max and gain in VO2max
was inversely related with age among subjects aged 61 to 78
years. They also found that the length of the training intervention
correlated with age the shortest training programmes been
performed among older subjects. It was suggested that the
lower gain in older people was because of the shorter duration
of their programmes. In the meta-analysis 14 out of 29 studies
were conducted without a control group and only 3 out of 29
studies were done among subjects older than 75 years. Furthermore,
exercise intensity and VO2max was variously reported
in the studies included in this meta-analysis (Green and Crouse,
1995).
Exercise intensity, duration, frequency and length of exercise
regimen are critical factors for the size of the gain in aerobic
fitness following endurance exercise training among elderly
people. In the meta-analysis by Green and Crouse (1995) mean duration of exercise was 32 minutes (range 12.5
- 60 min) per session and mean frequency of exercise was 3
times per week (range 2.5 -5.0). The mean length of the training
regimen was 26 weeks (range 6 - 60 weeks). Unfortunately,
the authors were unable to precisely quantify and code the
exercise in these training studies. In the discussion the
authors mention that eight different methods of prescribing
intensity were used in these studies.
The frequency of the training in study 3 was 2 times per week
in the 2-week orientation phase and 3 times per week in the
16-week training phase. The intensity of endurance exercise
in study 3 was gradually increased from 50 to 80 of the initial
heart rate reserve. The heart rate reserve method was used
because it served to set reasonable training limits when compared
to the corresponding oxygen uptake levels. It has been recently
suggested that the percentage of maximal heart rate is the
preferred method as it has been found to be more accurately
related to oxygen uptake than the HRR method in older women
and men (Kohrt et al., 1993; Kohrt et al., 1998; Panton et al., 1996). Puggaard et al. (2000) found an 18% improvement in VO2max among 55
women aged 85 years following 8 months' endurance exercise
training at an intensity of 69% of the HRmax. Morey
et al. (1999) reported an 11% increase in VO2max after 3
months' aerobic-only training at 70% of HRR among 134 subjects
(both men and women) aged over 64 years. Malbut et al. (2002) found a 15% increase in VO2max among women
and no gain in men aged 79 to 91 years with a combined 24-week
endurance and strength training programme at an RPE between
13 and 15. The women's initial mean VO2max was
only about 14 ml·kg-1·min-1, and therefore
a further gain was likely to occur.
The gain in cardiovascular fitness was low in the training
groups in study 3 when compared to results of earlier studies.
It is probable that the low increase in aerobic capacity was
due to the shorter duration of the exercise training programme
in study 3. However, cardiovascular fitness declined during
the intervention in the control group. The overall effect
of training on cardiovascular fitness can be thus considered
beneficial and significant. The basal peak oxygen uptake among
the subjects in study 3 was 17-18 ml·kg-1·min-1.
Even a small increase in elderly people may be enough to offset
the deleterious effects of ageing. In the oldest old people
maintaining a constant level of physical capacity over the
final years of life may be an acceptable aim.
The effects of endurance and strength training on cardiovascular
fitness may be more pronounced at the submaximal than maximal
level of effort. In study 3 the average distance walked during
the training sessions (endurance group) increased from 1500m
(range 1200-2200m) to 2700m (range 2400-3300m) over the training
period. Walking time increased from 20 to 30 min and training
intensity from 50 to 80% of the initial heart rate reserve.
When these facts are taken into account there is no clear
evidence that submaximal working capacity increased in our
subjects in the endurance group. In addition, our peak oxygen
uptake values would represent submaximal aerobic capacity
if RER (respiratory exchange) figures are taken into account
(Table 19). It should
also be kept in mind that present peak oxygen uptake values
do not represent a pure measure of cardiovascular fitness
but a combined measure of cardiovascular fitness, function
and health. This is because a considerable number of the exercise
tests were stopped for medical or other reasons. Peak HR was
lower in the final exercise test in all 3 study groups. This
was found not to be an indication of submaximal exercise levels
in the endurance and strength training groups but due to the
increased effect of ß- blocking medication. One subject in
the control groups stopped the exercise test in the early
phase because of deep ST segment depression.
Strength training increased cycling power in study 3. Strength
training may also stimulate the cardiovascular system and
type I muscle fibres (slow-twitch) resulting in an increase
in aerobic capacity. Other studies have also found an increase
in endurance working capacity following strength training
(Ades et al., 1996; Hepple et al., 1997). An increase in muscular endurance in the lower extremities
makes it possible to achieve a higher work load in a cycle
ergometer test. These findings suggest that improved endurance
is not a function of cardiovascular fitness alone but can
be significantly enhanced by increased muscular strength.
The subjects in the endurance group also showed increased
strength in the lower extremities. This could be due to the
step aerobic training performed in the endurance group inducing
a significant resistive stimulus in the muscles of the lower
extremities.
Possible
adverse effects of exercise
Adverse cardiac effects in exercise tests among elderly men
and women (Study 4)
Acute physical exertion increases the likelihood of cardiovascular
disturbances and sudden cardiac death. These adverse effects
seem to be more pronounced among older than younger people
(Gibbons et al., 1989; Mayuga et al., 1996).
A low frequency of cardiovascular complications in relation
to exercise testing has mostly been reported in various study
populations (ACSM, 2000).
These studies have mostly been performed among selected groups
and among subjects younger than 75 years. In study 2 the exercise
tests were stopped in a considerable proportion of cases because
of cardiac arrhythmia or ST segment changes. No complex cardiac
arrhythmia or cardiovascular disturbances were detected. Cardiac
arrhythmia and ST segment depressions were principally seen
in close temporal proximity to exercise, i.e. during or 2
hours before or after exercise. These findings are well in
line with earlier studies (Kennedy et al., 1977;
Mittleman et al., 1993).
An increasing number of ventricular premature beats or multifocal
ventricular premature beats were a more common reason for
exercise test cessation among men than women. The same gender
difference has also been found in another study (Hollenberg
et al., 1998).
It is suggested that this gender difference is due to the
longer duration of the exercise test among men than among
women. No exercise test- related complex arrhythmia or symptomatic
ST segment depression was seen among elderly men and women.
One subject in the population group, however, was referred
to hospital because of acute atrial fibrillation when doing
the test. This subject was treated successfully in the hospital.
No other referrals to hospital were found in the hospital
register check. The relatively high number of cases of cardiac
arrhythmia events in relation to exercise tests generally
calls for cardiac monitoring and careful clinical supervision
both during exercise and in the immediate post-exercise cooling
down period.
Medical problems during strength and endurance training
programmes (Study 3)
Our subjects were medically screened according to standard
criteria, the training supervised and the exercise programs
individually tailored. In spite of these procedures there
were five cases of cardio- or cerebrovascular health problems
in the exercise groups. The rate of these health problems
is among the highest reported in the existing exercise training
studies among elderly people. Whether it was the physical
training that caused these health problems is a difficult
question to answer with any degree of certainty. Health problems
of these kinds were likely to emerge in a larger group of
subjects in exercise groups. Health changes in elderly women
quite commonly manifest themselves within a relatively short
period of time during normal life. It is more probable that
declining health and symptoms of disease are detected better
in elderly individuals engaging in physical training than
among sedentary subjects. This is because the symptoms of
the disease tend to become evident during physical exertion.
In no cases among the present subjects were the incidents
directly related to physical effort. In addition, on the basis
of the distribution of the clinical findings in the exercise
tests no adverse effects of exercise training on cardiovascular
response were detected. However one subject in the control
group had to stop the final exercise test suddenly because
of deep ST segment depression. No cardiovascular complaints
during the exercise sessions were detected. When asked by
questionnaire, almost all of the subjects in the training
groups considered the training beneficial to their fitness
and health.
Most of the health problems emerged in the strength training
group. The safety of strength training among healthy individuals
seems to be well established. However, the effectiveness and
safety of strength training among older subjects with low
aerobic capacity has not been clarified (Pollock et al., 2000).
Most of our subjects were slightly hypertensive and suffering
from prevalent or latent atherosclerosis. This may increase
the likelihood of cardio- or cerebrovascular events. An abrupt
increase in aortic pressure due to the reflecting pressure
wave component from the abdominal aorta meeting the systolic
pressure wave has been shown in elderly subjects (O'Rourke
1990).
Holding one's breath when making a physical effort considerably
increases arterial pressure. These factors may have contributed
to arterial wall damage and the incidence of cardio- or cerebrovascular
disease. After one case of heart infarction and death the
strength training programme was modified to exclude training
directed at the trunk muscles. In addition, the subjects were
asked not to hold their breath when performing the strength
training exercises.
At the beginning of the programmes a 2-week orientation phase
was used in which the frequency and intensity of the training
was reduced. The newly revised ACSM guidelines for strength
training in the elderly recommend a minimal resistance for
the first 8 weeks to allow for connective tissue adaptations
(ACSM, 2000).
This is to avoid the kinds to musculoskeletal problems which
also emerged during the training programme. It is unclear
whether this is also of importance in avoiding cardiovascular
problems.
With reference to the dose-response curves (Kallinen and Alen,
1995,
Figure 1) it seems that
among elderly people the beneficial and adverse effects of
exercise emerge at lower doses of exercise than in younger
people. Nevertheless, it is questionable whether a general
dose-response curve could be set for a rather heterogeneous
group of elderly people. The results of the training study
showed that the responses of physical exercise on cardiovascular
fitness, and perhaps on health as well were individually very
variable and non-predictable. It is possible that both genetic,
age- and disease-related factors determine the responses to
physical exercise and that these effects can be quite fortuitous
as far as the individual is concerned.
Value of exercise testing among elderly people (Study 2,
4)
The research results suggest that exercise testing was found
useful from two points of views. At first, high occurrence
of cardiac arrhythmia in relation to exercise testing, especially
in elderly men, calls for cardiac monitoring during exercise
testing and the immediate post-exercise recovery period (study
4). Although the data did not confirm that these cardiac disturbances
were serious manifestations of an underlying cardiovascular
disease, the data neither support the omission of ECG and
blood pressure monitoring during maximal exercise testing
among elderly people. Moreover, in some of elderly subjects,
exercise ECG may reveal complex and life-threatening arrhythmias.
These can be treated with modern medical technology or drugs.
In accordance with the guidelines issued by ACSM and AHA ,
for safety reasons exercise testing with cardiac monitoring
remains a recommendation for elderly people embarking on a
vigorous exercise programme.
The most noteworthy finding in study 2 was that low exercise
capacity in relation to cycle ergometric testing was a strong
and independent predictor of death. Exercise testing provides
prognostic information and is thus useful for elderly people
in risk stratification. The usefulness of this information
is, however, unclear. Whether we can prevent premature death
in elderly people by increasing exercise capacity through
exercise training or more active medical treatment remains
an open question.
Elderly people are not a homogenous group in their physical
capacity and health. A considerable proportion of the elderly
cannot be tested (28% in study 2) by the usual methods of
exercise testing. Those subjects excluded from exercise testing
were found to be at increased risk for death (study 2). Thus,
clinical assessment prior to exercise testing was also found
useful in risk assessment. The preventive measures should
be directed first to those people excluded from the exercise
test. On the other hand, more sophisticated methods are needed
to assess physical capacity in elderly people. The selection
of the method of functional or physical capacity should be
individualized in elderly people. The physical capacity of
those with poor health and impairment in the management in
activities in daily living can be assessed by questionnaires,
interview, by direct observation in daily living or by simple
functional capacity tests (Spirduso, 1995).
When diagnostic procedures are needed pharmacologic testing
is a method of choice among the elderly people who cannot
be tested by conventional methods of exercise testing.
Plasma C-ANP and N-ANP as markers of cardiac load during
exercise tests (Study 1)
Plasma N-ANP concentration has been found to be an accurate
measure of symptomless left-ventricular cardiac dysfunction
(Lerman et al., 1993).
Both the C-ANP and N-ANP increased by physical loading in
study 3. This is well in line with earlier studies (Freund
et al., 1988;
Baker et al., 1991;
Mandroukas et al., 1995).
The percentage increase in C-ANP correlated with a few physiological
variables e.g. cycling power in W·kg-1 body weight.
A corresponding association with N-ANP was not found. It is
suggested that C-ANP may be more sensitive to acute response
than N-ANP which has 5-10 times longer half-life than C-ANP
(Thibault et al., 1988).
The differences in the C-ANP and N-ANP responses may be due
to postsecretory mechanisms.
The basal N-ANP concentrations in study 1 were highest in
those physically active elderly whose exercise test was prematurely
terminated. Does a high basal N-ANP level predict a premature
exercise termination? Variable reasons were, however, associated
with high basal levels of N-ANP in this group. Also in the
control women a corresponding association with high basal
levels of N-ANP and prematurely terminated exercise test was
not found. To clarify the reason for this need further studies
with more precise evaluation of cardiac function.
Methodological considerations
A population-based approach was taken to study the beneficial
or possible harmful effects of exercise on the health of elderly
people. In studies 2, 3, 4 the basic study group comprised
of a representative sample taken from a population register.
In study 1 the sedentary control women were randomly taken
from a population register of the rural municipality of Jyväskylä.
Physically active women in study 1 were selected from a sample
of 600 members of Finnish sport organisations on the basis
of physical activity questionnaire. The most physically active
were invited to further studies. The subjects of this study
are thus representative of either the normal population or
the subset of physically active persons. Such a method of
subject recruitment forms a good basis for generalizing the
results.
Our criteria for exclusion or from stopping the exercise test
were based on the guidelines issued by American College of
Sports Medicine (American College of Sports Medicine, ACSM,
1986).
These guidelines have remained largely unchanged the past
14 years (American College of Sports Medicine, ACSM,
2000).
The relative exclusion criteria and indications for stopping
the test in the ACSM 2000
guidelines were all incorporated in the guidelines used in
this research. Some differences, however, existed between
our and the ACSM 2000
guidelines. Electrolyte abnormalities and chronic infectious
disease (mononucleosis, hepatitis, AIDS) are listed in the
contraindication list as relative contraindications but were
absent in our list (ACSM, 2000).
Subject refusal, left bundle branch block and anaemia (hemoglobin
under 100 g·l-1) were listed in our list of contraindications
but are missing in the ACSM 2000
guidelines. Furthermore, in the ACSM 2000
recent myocardial infarction (within 2 days) or other cardiac
event is an absolute contraindication for the exercise test.
In our list recent (under 3 months) or suspected myocardial
infarction is an absolute contraindication (Table
10). Acute pulmonary embolus or pulmonary infarction is
an absolute contraindication in the ACSM 2000
guidelines, but the time after which the exercise test can
be performed is not defined. In our guidelines this was within
6 months of the incidence (Table
10). Technical difficulties, ST segment elevation (>
1mm in other leads than V1 and aVR) were listed as absolute
indication for stopping the test but were missing in our list
(Table 11). R on T premature
ventricular beats and severe pain in musculoskeletal system
were included in our list of indications for stopping the
test but are missing in the ACSM 2000
guidelines.
In study 1 some technical difficulties were encountered in
measuring oxygen uptake directly in all of the subjects. The
mouthpiece felt uncomfortable to some of the subjects, so
we had to use an air-cushioned mask, which had to be positioned
very carefully to avoid leakage of air from the mask. In spite
of these precautions, it was impossible to measure the direct
oxygen uptake in seven of the physically active women and
nine of the control women.
The dose and duration of the strength and endurance exercise
training used in this study (study 3) was sufficient for the
improvement of cardiovascular fitness and muscular strength
on the basis of the earlier studies (Charette et al., 1991;
Shephard 1997b;
McCartney et al., 1995;
Taaffe 1996).
The large variation in responses and the small number of subjects
may limit the statistical power of these exercise effects.
Furthermore, the subject's initial exercise capacity and physical
activity level can modify the gain in exercise capacity. In
the present study no significant correlation was in fact found
between relative increase in aerobic capacity and initial
exercise capacity or physical activity level. The effects
of strength and endurance training on cardiovascular fitness
may be influenced by differences in the level of loading of
the initial and later exercise tests. The peak RER values
were, however, comparable during the initial and later cycle
ergometer tests. The RER values suggest that many of the exercise
tests were submaximal and prematurely terminated because of
abnormal cardiovascular responses. It is probable that low
effort tolerance and decreased health hinder elderly women
from being prescribed a sufficient exercise dose.
Strengths
and weaknesses of the research
One of the main strengths of the present research is that
a population-based approach was taken. Effort tolerance and
cardiovascular responses to acute exercise were studied in
relation to the whole-population study in the selected age-group.
Few population-based studies have been performed to confirm
the safety, substantial and consistent beneficial effects
of physical exercise on cardiovascular functions and fitness.
Earlier studies have been performed among selected populations
with few or no health problems. Ageing, diseases, medications
and physical activity level evidently modify the acute and
prolonged effects of exercise on cardiovascular functions.
There are, however, a number of factors which may complicate
the interpretation of the results in population level studies.
The heterogeneity of the population group means wide variation
in the response, leading to loss of statistical significance.
The drop-out rate in the training study raises doubts about
the feasibility of the physical exercise among elderly populations
even though the over-all effects of the present exercise were
beneficial.
The mortality analysis in study 2 suffers from several methodological
limitations. First, the low number of study subjects did not
allow us to utilise other kinds of information, such as socio-economic
factors, severity of disease, dietary factors, and alcohol
consumption as cofounders influencing mortality. In addition,
non-medical reasons for excluding subjects from the exercise
test or for terminating the test render the interpretation
of the data difficult. The subjects were representative only
of a one-year birth cohort living in a small geographical
area. Studying more people across a broader age range and
over a larger geographical area would have allowed us to generalise
the findings among elderly people with more certainty.
In the exercise intervention study we used a control group
with randomisation. This is essential if the true effects
of exercise are to be established in an elderly population
in which decline in physical performance with ageing may occur
in a relatively short period of time. The randomisation of
the subjects was successful, because the groups did not differ
significantly from each other at the baseline in relation
to the variables used. Furthermore, no major changes in overall
physical activity level were found in the control group. The
controls simply continued to function at their habitual physical
activity level and did not increase it.
Common standard exclusion criteria (ACSM) for physical exercise
were used in this research. Efforts were made to ensure thorough
medical supervision and careful monitoring of the subjects
during the exercise test and training program. The adverse
effects of exercise were detected by direct immediate monitoring,
by ambulatory 24-hour monitoring, repeated clinical examinations,
and also by checking the patient registers in the local hospital.
By this way any immediate or prolonged adverse effect could
be detected. Every exercise dose was also individually tailored
according to commonly used guidelines. It is difficult to
see improvement could in relation to the exclusion criteria
and safety monitoring. However, our studies were performed
a few years ago and the guidelines and methods used today
are not exactly the same (see methodological considerations
above). Different cohorts of elderly people may be different
in health, medication, and levels of physical activity and
thus show different responses to physical exercise.
A further weakness in this research concerns the relatively
narrow age range (76 to 78 years) in the exercise intervention
study. The responses to exercise training may differ between
subjects under 70 years and those 80 years or older. The effects
of physical training may also differ between the sexes. The
effects of exercise training were studied only among elderly
women.
Practical implications and suggestions for further research
Physically active elderly women had a markedly higher cardiovascular
fitness and effort tolerance in the cycle ergometer test than
their physically less active controls. This finding supports
the argument that prolonged physical training together with
better trainability results in improved cardiovascular performance
and effort tolerance. The percentage increase in plasma C-ANP
had a significant association with watts per kg body weight
in the cycle ergometer tests among both the physically active
and control women. C-ANP may be a useful measure of cardiac
load in the context of exercise tests in elderly people.
High cycling power in the ergometer test was found to be strongly
and independently associated with decreased mortality in both
elderly men and women. The non-exercise test subjects were
at an increased risk for death. The subjects with premature
exercise test termination did not have excessive mortality
compared to those with non-terminated tests. Exercise testing
thus provides information on the risk for death that is incremental
to clinical data and traditional risk factors in elderly people.
The 18-week endurance and strength training programmes resulted
in a small and individually variable increase in cardiovascular
fitness (peak oxygen uptake). It is noticeable that both endurance
and strength training resulted in a significant increase in
cycling power (watts per kg body weight) compared to the change
in the control group. Strength training was directed at increasing
the strength of the lower extremities, which is one of the
important factors that determinants of performance in the
cycle ergometer test. Strength training also resulted in a
significant decrease in body fat compared to the corresponding
change in the control group. Although the beneficial effects
of strength and endurance training were quite small, both
training methods are considered useful mean of resisting the
deleterious effects of ageing on body composition and physical
performance.
A considerable number of the exercise tests were terminated
for cardiac arrhythmia and deep ST segment depressions. Although
most of the cardiac disturbances were benign in nature, medical
supervision and cardiovascular monitoring is recommended among
people older than 65 years during maximal exercise tests.
The ambulatory ECG recordings showed that the progressive
exercise tests did not have a long-lasting increasing effect
on cardiac disturbances among these elderly subjects. In some
of the subjects, however, cardiac disturbances tended to occur
within a period of 2 hours before and after the exercise test.
Exercise-tested elderly persons should therefore remain under
supervision during the immediate and late recovery period.
No serious complications were found in these studies in relation
to the progressive cycle ergometer tests. Elderly subjects
relatively seldom reach their peak aerobic capacity in exercise
tests, which may be one factor protecting them against serious
complications during such tests. During the strength and endurance
training programmes all of the cardio- or cerebrovascular
problems occurred unexpectedly in subjects who initially did
not manifest that particular health problem. Are elderly people
more prone to health problems with repeated physical loading
than we have thought so far? How can such events be prevented
and what are the optimal dose-response relationships in elderly
people with low cardiovascular fitness and health problems?
What factors influence individual responses to physical exercise
in relation to physical performance and health? These are
important questions that remain to be addressed in future
studies.
|
CONCLUSIONS |
1.
Forty-eight percent of the exercise tests among physically
active women and 14% in the less active control women continued
to the objective maximum. In the maximal exercise tests mean
peak oxygen uptake was 26.2 and 18.7 ml·kg-1·min-1 among the
physically active women and control women, respectively. A
markedly higher effort tolerance and aerobic capacity was
found among the physically active compared to less active
control women.
2. High physical capacity in the cycle ergometer test
was independently associated with decreased mortality among
elderly people. Exercise testing provides prognostic information
that is incremental to clinical data and traditional risk
factors for death.
3. The 18-week strength training resulted in a 9.4%
increase in peak oxygen uptake while the endurance training
improved peak oxygen uptake by 6.8%. A statistically significant
increase in cycling power in watts per kg body weight was
found in the strength training group compared to changes in
the control group. A corresponding increase was also found
in the endurance training group. Both endurance and strength
training increased performance in the cycle ergometer test.
The effect of the 18-week endurance and strength training
programmes on peak oxygen uptake could, however, considered
small in comparison to levels found in earlier studies.
4. Twenty-three percent of the cycle ergometric testing
in the elderly men was stopped because of cardiac arrhythmia
or ST segment depressions. In the elderly women the corresponding
proportion was 7%. A considerable number of exercise tests
in elderly people, especially among elderly men, are prematurely
terminated because of cardiac disturbances. Cardiovascular
monitoring is recommended in relation to exercise testing
in elderly people for safety reasons.
5. Five cases of cardio- or cerebrovascular health
problems emerged in the exercise training groups. These health
problems were not directly related to physical exertion. Nevertheless,
the adverse effects of repeated physical exercise cannot be
ruled out.
6. The overall dose-response relationships of physical
exercise need further clarification among elderly people in
population-based, randomised controlled trials.
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ACKNOWLEDGMENTS |
The
present research project was carried out in the Department of
Health Sciences, University of Jyväskylä, Research Centre for
Interdisciplinary Gerontology, and LIKES-Research Center for
Sport and Health Sciences.
I owe my deepest gratitude to my supervisors Professors Eino
Heikkinen, the former Head of the Department of Health Sciences,
Rainer Rauramaa, Head of the Kuopio Research Institute of Exercise
Medicine, and Harri Suominen, Head of the Department of Health
Sciences, University of Jyväskylä.
I express sincere thanks to Professors Arthur S. Leon and Archie
Young who reviewed the manuscript of the thesis and gave me
valuable criticism and suggestions for the completion of the
work.
I gratefully acknowledge Professor Markku Alen, Kuopio Research
Institute of Exercise Medicine and Professor Veikko Vihko, Head
of the LIKES- Research Center for their material and mental
support during my studies. Drs Pertti Era and Sarianna Sipilä
are warmly acknowledged for their contribution as co-authors
and for practical work in the experimental part of the studies.
I thank Markku Kauppinen, Jouni Mutka and Tommi Salmela for
their work in the statistical analysis of the data.
I thank physiologists Ensio Hakala, Eino Havas, Tapani Keränen,
Raija Leinonen and Paavo Rahkila for their advice, technical
support or assistance during the ergometry tests. I also thank
Markku Pirnes for analysing the ambulatory ECG recordings. Tuija
Luokkanen, Eva Mannila, and Hanna Tuominen are greatly acknowledged
for their conscientious work in the exercise intervention study.
Michael Freeman has carefully checked the language of my manuscripts
and also taught me different ways to express my thoughts in
English.
Without financial support from the Academy of Finland, Ministry
of Education, Finland, Ministry of Social Affairs and Health,
Finland, City of Jyväskylä, Peurunka Rehabilitation foundation,
and Central Finland Health Care District this research project
would never have been realised.
The research project has taken not only money but also a lot
of time. In the short story entitled "Tulitikkuja lainaamassa"
("Borrowing matches" ) by the famous Finnish writer
(Lassila, 1910) a man goes out into the neighbourhood to borrow
matches. The man forgets what he has gone out for because of
the many interesting people he meets and the things that happen
to him. The same thing has happened to me during this long research
project. Producing a thesis is not my primary goal in life.
It is to find new and interesting things.
Jyväskylä
, November , 2004
Mauri
Kallinen
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AUTHOR
BIOGRAPHY |
Mauri KALLINEN
Employment: Central Finland Health Care District
Degree: MD
Research interests: Exercise medicine in the elderly
Email: mauri.kallinen@fimnet.fi
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