PHYSIOLOGICAL RESPONSES AND MOOD STATES AFTER DAILY REPEATED PROLONGED
dissertation presented on the 8th of May 2004 at the the Faculty
of Medicine of the University of Kuopio, Finland, by permission
of LIKES - Research Reports on Sport and Health, Finland. LIKES
- Research Reports on Sport and Health 160.
Department of Physiology, Faculty of Medicine, University of Kuopio, Kuopio
LIKES-Research Center for Sport and Health Sciences, Jyväskylä, Finland
© Journal of Sports Science
and Medicine (2004) 3, Suppl.6, 1 - 43
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review is based on the following orginal publications, which will be referred
to in the text as Studies 1-6:
I., Mäntysaari, M., Huttunen, P., Komulainen, J. and Vihko, V. (1997)
The effects of a 4-day march on the lower extremities and hormonal balance.
Military Medicine 162, 118-122.
I., Vasankari, T., Mäntysaari, M. and Vihko, V. The effects of a 4-day
march on the gonadotrophins and mood states of military men. Military
Medicine 169 (in press).
I., Mäntysaari, M. and Vihko, V. (2001) Soldiers' physiological and psychological
loading during a 4-day march. Annales Medicinae MIlitaris Fenniae
I., Vasankari, T., Mäntysaari, M. and Vihko, V (2002) Hormonal responses
to daily strenuous walking during 4 successive days. European Journal
of Applied Physiology 88, 122-127.
I. and Vihko, V. Physiological and psychological responses to 100 km cross-country
skiing during 2 days. Journal of Sports Medicine and Physical Fitness
I., Vasankari, T., Mäntysaari, M. and Vihko, V. Hormonal responses to
100 km cross-country skiing during 2 days. Journal of Sports Medicine
and Physical Fitness (in press).
purpose of this study was to describe the physiological responses
to daily repeated acute but non-competitive prolonged exercise during
a 4-day march and a 2-day cross-country ski event to the cardiorespiratory,
autonomic nervous, musculoskeletal and endocrine systems. Mood states
were also evaluated after these repeated exercises.
The data of these short-term follow-up (reversal) field trials was
collected from healthy, 23 to 48 year old Finnish male soldiers
in 1993 (n=6) and 1994 (n=15) during the "International Four-Day
Long-Distance March" in Nijmegen, The Netherlands, and from
ten healthy, 22 to 48 year old Finnish male participants in 1995
during a 2-day Finlandia Ski Race in Lahti, Finland.
Acute cardiovascular responses were estimated by measuring the heart
rate during exercise. The responses of the autonomic nervous system
were estimated by measuring the heart rates during the orthostatic
test. The musculoskeletal responses were estimated by measuring
the perceived pains, flexibility, functional strength, use of elastic
energy and oedemic changes of the lower extremities. Hormonal responses
were estimated from the urinary excretion of catecholamines, and
the concentrations of serum cortisol, testosterone, luteinizing
(LH) and follicle stimulating hormone (FSH). Mood states were assessed
with the Profile of Mood States (POMS) questionnaire.
Daily walking time was 7-10 hours while the skiing time was 3 hours.
Average heart rate during walking was 59% and skiing 87% of maximum
heart rate. Morning heart rate in the supine position increased
progressively through the marching period but not through the skiing
experiment. After the first day, perceived pain increased significantly
and remained at a similarly increased level until the end of the
exercise period. Leg measurements showed no signs of oedema, decreases
in flexibility, or functional strength. Catecholamine excretion
rates during marches indicated cumulatively increased sympathoadrenal
stress. The acute increasing effect of a single walking session
on cortisol was seen only after the first day when there was a 60%
increase. Responses after skiing were greater (2.2- and 2.6-fold).
The acute reductions in testosterone concentrations were seen after
the first two marching sessions, when they were decreased by 18-22%.
LH concentration was decreased by 31-44% after the second and third
day. For FSH concentrations suppression was consistently seen after
the second march, but not after skiing. The total mood disturbance
score remained unchanged during the events. The Fatigue-Inertia
affective state was higher after exercise than before the events.
This study demonstrates that the pituitary-gonadal axis, excluding
the secretion of FSH and the adrenal cortex, adapted to four days
of repeated moderate 8 h walking, but not to two days of repeated
strenuous 3 h skiing. However, when using the sensitive IFMA, which
can detect low concentrations of gonadotropins, secretion of FSH
was seen to remain reduced and no adaptation was seen in walking.
This study indicated that daily repeated long lasting acute but
non-competitive walk and skiing of intensity at approximately 60-90%
of the maximum heart rate is well within the physiological capabilities
of individuals with good aerobic capacity.
WORDS: Hormones, functional capacity, lower extremities, muscle
soreness, mood state, adaptation, recovery, walking, skiing.
human organism is in a homeodynamic state. When extrinsic or intrinsic
forces threaten homeostasis, the state is called stress. Stress
is defined as a physical, chemical, or psychological factor or combination
of factors, which pose a threat to the homeostasis, or well-being
of an organism. Stress produces a defensive response of which infection,
physical or emotional traumas are examples (International dictionary
of medicine and biology in three volumes, 1986,
p. 2719). A nongenetic change in an organism, which takes place
in response to an environmental stimulus and a progressive reduction
in the sensitivity of a sense organ following prolonged exposure
to the same sensory stimulus, is defined as adaptation (International
dictionary of medicine and biology in three volumes, 1986, p. 39).
According to Physical Stress Theory (PST) (Mueller and Maluf, 2002) tissue adaptation takes
place in response to physical stress. The level of exposure to physical
stress is a composite value, defined by the magnitude, time and
direction of stress application. Physical activity normally improves
health by increasing the stress threshold on a broad range of tissues,
making them more tolerant of subsequent physical activity and thereby
less likely to be injured. However, if tissues are unable to adapt
to meet the demands of a given posture or task, injury occurs. For
example, injury can occur, if a high- magnitude stress is applied
for a brief duration or a low-magnitude stress is applied for a
long duration, and if a moderate-magnitude stress is applied to
the tissue many times. In exercise loading, attention focuses on
factors such as the frequency and length of workouts, the type of
exercise as well as the speed, intensity, duration and repetition
of the activity. In the recovery phase, homeostasis must be re-established
to allow the body to respond to stress so that adaptation can occur.
The regenerative process still continues after the restoration of
the previous homeostatic state with a resulting overcompensation
or supercompensation (Harre, 1975; Viru, 1984). Ideally, subsequent exercise/training
session should not take place until supercompensation has occurred
(Harre, 1975). Among physiological responses to exercise there
are also psychological responses, which are usually explained by
endorphin, monoamine, thermogenic or distraction hypothesis, or
opponent-process model (Leith, 1994).
The acute effects of a single bout of several types of physical
exertion and the effects of long-term physical training are quite
well documented. Far less is known about the responses to daily
repeated strenuous physical exertion and the loading versus recovery/adaptation.
Physiological responses in professional athletes, of daily repeated
running and cycling are quite well known, however very few investigator,
have attempted to assess both physiological and psychological parameters
during periods of overloading micro-cycle exercising, despite the
demonstrated efficacy of such an approach within recommendations
and within exercise and sport science research (e.g., O'Connor et
al., 1989; Fry
et al., 1991;
Hooper and McKinnon, 1995).
There are countless numbers of sustained extreme exercises to participate
in for cyclists, orienteers, paddlers, rowers, skaters, skiers,
swimmers, walkers and other extreme seekers in the world. Many of
these events are favoured not only by regularly training and competitive
athletes but also by the population at large.
In exercise physiology applied research tends to address immediate
problems, to real-world settings. Quasi-experimental design fits
to settings that are more real world while still controlling as
many of the threats to internal validity as possible. It has less
control over the research settings than traditional experimental
designs, but it gives results that are of direct value to practitioners
(Thomas and Nelson, 1990,
p. 5). Because it is a natural research setting in which the experimental
design is introduced into the data collection procedure, a short-term
follow-up (reversal) field trial was used in this thesis. The general
purpose was to describe the daily physiological responses and to
understand the contextual action during the prolonged daily physical
stress more holistically. Further, psychological loading and responses
to mood states after repeated various (intensity, duration, mode/
type) prolonged exercises of healthy men were estimated.
OF THE LITERATURE
The term load is defined as external forces, which act upon
a body (Nigg et al., 1984)
whereas overload is a load greater than the rated load, which
can cause damage. Overloading is the condition resulting from
excessive sensory stimulation, in which the stimuli are too intense
or too rapid for an individual to respond appropriately. (International
dictionary of medicine and biology in three volumes, 1986,
Homeostasis is the relative stability or constant condition
(homeodynamics) of the internal environment of an organism, which
is preserved through feedback mechanisms despite the presence of influences
capable of causing profound changes and those processes considered
collectively by normal organisms which homeostasis is maintained (International
dictionary of medicine and biology in three volumes, p. 1986,
1331; Guyton and Hall, 2000,
Steady state is any condition which remains constant at a given
point in time because of the presence of opposite forces on processes
which cancel out one another's effects (International dictionary of
medicine and biology in three volumes, 1986,
Supercompensation is a state of improved work capacity, above
the level of which the person has recently been capable. This has
been characterised as a state of balanced homeostasis with homeostatic
markers reflecting either baseline values or improvements, depending
upon the nature of the variable (Fry et al., 1991).
Adaptation is the advantageous change or changes of behaviour,
physiology, or structure by which an organism modifies itself to fit
into a particular environment. A nongenetic change in an organism
which takes place in response to an environmental stimulus and a progressive
reduction in the sensitivity of a sense organ following prolonged
exposure to the same sensory stimulus are also defined as adaptation
(International dictionary of medicine and biology in three volumes,
1986, p. 39).
Physical activity (PA) is defined as any body movement produced
by contraction of skeletal muscle, which substantially increases energy
expenditure. The dose is described by intensity, frequency,
duration, mode/type, and purpose of the PA (Bouchard and Shephard,
1994; U.S. Department of Health
and Human Services, 1996;
Howley, 2001). Frequency is described as the number of
activity sessions per day, week, or month. Duration typically refers
to the length of activity in each session. Intensity describes,
in relative or absolute terms, the effort associated with the PA (Howley,
2001). Physical activity is frequently categorised by
the context in which it occurs (U.S. Department of Health and Human
Leisure-time physical activity (LTPA) is a broad descriptor of
the activities one participates in during their free time (e.g., dance,
gardening, hiking, walking, etc.) based on personal interests and
needs. The common element between these activities is the resulting
increased energy expenditure, although the intensity and duration
can vary considerably (Bouchard and Shephard, 1994, 77). The absolute intensity of LTPA describes the
actual rate of energy expenditure. Common expressions include: oxygen
uptake (l·min-1), oxygen uptake relative to body mass (ml·kg-1·min-1),
kcal or kJ per minute, and multiples of resting metabolic rate (METs)
Occupational physical activity (OPA) is associated with the
performance of a job, usually within the time frame of an 8-h work
day (Howley, 2001).
Training is the result of biological adaptations achieved after
repeated exercise bouts over a period of several days, weeks, or months
of exercise (Edington and Edgerton, 1976, p. 8).
Exercise (exercise training) is usually performed on a repeated
basis over an extended period of time. It is planned, and structured
to improve or maintain one or more components of physical fitness
(Bouchard and Shephard, 1994; U.S. Department of Health And Human Services, 1996).
Different exercises have different biological requirements. These
requirements could be classified according to the speed of movement,
resistance to the movement, and duration or time over which the movement
is repeated (Edington and Edgerton, 1976, p. 4-7). To understand the
suitability of a given exercise, we must understand the specific effects
of that exercise-form from the molecular level to the effects on the
total body (Edington and Edgerton, 1976, p. 4).
Overloading training is the process of stressing an individual
to provide a stimulus for adaptation and supercompensation (Fry et
al., 1991). Training
fatigue/stress is the normal fatigue that is experienced following
several days of this kind of heavy training associated with an overloading
stimulus. This fatigue is reversed and supercompensation occurs by
the end of the last few days of a period of reduced training load
(regeneration microcycle) (Kuipers and Keizer, 1988; Fry et al., 1991). Exhaustion is the
result of the body's inability to meet the exercise demands (Edington
and Edgerton, 1976,
Overtraining and physical overstrain are the non-differentiated
general terms for any short- or long-term condition which indicates
that the individual has been stressed by training and extraneous stressors
to the extent that a person cannot perform at an optimum level following
an appropriate regeneration period (Kuipers and Keizer, 1988;
Fry et al., 1991;
U.S. Department of Health and Human Services, 1996).
Overreaching is the state in which an accumulation of training
stress results in a short-term deterioration of performance capacity
with or without related physiological and psychological signs and
symptoms of overtraining, and in which the restoration of performance
capacity may take anywhere from several days to several weeks (Kuipers
and Keizer, 1988;
Budgett, 1990; Fry
et al., 1991; Fry
and Kraemer, 1997).
Overtraining syndrome and staleness are the states of
the long lasting imbalance between training and recovery. Muscular
overstrain occurs when the muscular stress tolerance is exceeded by
exercise, resulting in transient local fatigue and muscle soreness
thus it may be considered as local overtraining (Kuipers and Keizer,
Training stressors result from the physical, physiological, and
psychological training workloads administered during overload training.
Extraneous stressors are those resulting from activities and
psychological forces related to lifestyle (Fry et al., 1991).
Loading and adaptation mechanisms during physical activity
Load depends on the external and internal influences, as well as movement.
External parameters could be equipment (e.g., backpack), shoe and
surface. Internal factors are the anthropometrical facts and the individual
situation (from both a physiological and psychological point of view).
Movement may influence the load of the human body concerning the type
as well as the frequency of a certain type of movement (Nigg et al.,
1984). A specific
exercise will elicit a specific response in a specific individual
at a specific point in time (Edington and Edgerton, 1976,
p. 7). The attention in exercise loading focuses on factors such as
frequency and length of workouts, type of exercise, speed, intensity,
duration, and repetition of the activity. It also requires that the
progress of the load is observed, as well as the recovery intervals
If the volume of the physical activity is too large or the recovery
is too short, training can lead to problems. There are many risk factors
for training injuries, which could be categorised either as intrinsic
or extrinsic in nature (Jones and Knapik, 1999).
Intrinsic factors are the inherent characteristics of individuals,
anatomical characteristics, physical fitness, lifestyle and behavioural
characteristics. Extrinsic factors are external to the individual,
such as a physical training programme (e.g., high running mileage,
frequent marching and running), equipment, terrain and weather conditions,
which all influence the risk of injury.
The human body is able, to some degree, actively adapt to physical
stress. Adaptation to life conditions, change in the external environment
and any kind of bodily activity are always directed toward maintaining
or restoring the constancy of the body's internal milieu (Viru, 1984; Viru and Smirnova, 1995). In situations which require
the activation of adaptation processes, the main events within an
individual are described by Viru and Smirnova (1995)
in the following manner: "The agent (stressor) acts, by various
pathways, on the structures of the central nervous system. If the
required intensity of the homeostatic reactions is high, or it is
necessary to maintain them for a prolonged duration, the mechanisms
of general adaptation (mobilisation of energy reserves and protein
resources, and activation of defence faculties) will be activated."
During the recovery period after acute adaptation, and to a lesser
extent during acute adaptation, the dynamic reserves are used extensively
for the adaptative synthesis of the enzymes and structural proteins
to restore the functional capacity of cellular structures that had
been highly active during acute adaptation. Depending on the intensity
of the inductive stimulus of adaptive protein synthesis, it may result
in the production of such an amount of proteins as to warrant further
development of related functional possibilities. The latter is based
on the morphological and metabolic improvement. If the action inducing
such adaptive synthesis of proteins is repeated with sufficient frequency,
a stable adaptation develops together with elevated levels of morphological
and metabolic improvement of related cellular function. (Viru, 1984)
In Edington and Edgerton's (1976,
p. 10) model, daily exercise "sets up" the body so that
subcellular mechanisms are stimulated to bring about those adaptive
changes that characterise the "trained state". In other
words something specific about the act of the exercise stimulates
the cells to adapt so as to become better prepared to protect against
this same exercise stress. It is highly likely that the exercise "sets
up" the cell, while the actual adaptation occurs during the recovery
phase. Both short- and long-term adaptations take place in response
to an exercise stress. Short-term adaptations, which occur during
the actual exercise, mainly involve the conversion of an inactive
component to active chemicals. Long-term adaptations, which account
for the primary training adaptations, are mainly concerned with the
increased amounts of primary proteins (Edington and Edgerton, 1976,
The core principle of the Physical Stress Theory (PST) is the adaptation
in response to physical stress. The level of exposure to physical
stress is a composite value, defined by the magnitude, time and direction
of stress application (Mueller and Maluf, 2002).
Movement can have beneficial (e.g., hypertrophy) as well as detrimental
effects (e.g., overuse injury) on the tissues of the body. Changes
in the relative level of physical stress cause a predictable adaptive
response in biological tissues (epithelial, connective, muscular and
nervous), which combine to form organs (i.e., cardiorespiratory, integumentary,
musculoskeletal, and neuromuscular systems). The PST proposes that
tissues accommodate to physical stresses by altering their structure
and composition to best meet the mechanical demands of routine loading.
Deviations from routine or steady state loading provide a stimulus
for adaptation, which allows tissues to meet the mechanical demands
of a novel environment.
According to the PST, there are five characteristic responses to physical
stress: decreased stress tolerance, maintenance, increased stress
tolerance, injury and death (Mueller and Maluf, 2002).
Tissue homeostasis occurs when tissue degeneration equals tissue production.
The range of stress levels, which promotes tissue homeostasis, is
defined as the maintenance stress range. This steady state or equilibrium
response occurs when tissues are exposed to a level of stress to which
they have become accustomed to. When the maintenance range is exceeded,
it results in an increased tolerance of tissues to subsequent stresses.
Although overload can improve stress tolerance, adequate recovery
between bouts of increased stress is needed for this adaptive response
to occur. Excessively high levels of physical stress can result in
tissue injury. When tissues are unable to adapt to meet the demands
of a given posture or task, injury occurs.
Physiological responses to prolonged exercise
Response is characterised as any organic process elicited by a stimulus,
as a muscular or glandular process or as a biochemical or immunochemical
reaction (International dictionary of medicine and biology in three
volumes, 1986, p.
2471) where reaction is defined as any response to a stimulus or other
event (International dictionary of medicine and biology in three volumes,
1986, p. 2419).
When challenged with any physical task, the human body responds through
a series of integrated changes in function that involve most, if not
all, of its physiological systems (e.g., cardiorespiratory, nervous,
musculoskeletal, endocrine and immune systems) (U.S. Department of
Health And Human Services, 1996).
Physical exercise is a stimulus (stress) to which the body responds
through the so-called alarm reaction: energy yield is increased, requiring
muscles thus functional reserves are mobilized, hormones are secreted,
and defence mechanisms are activated (Selye, 1975;
Viru, 1984). These
responses are mediated by both neural and humoral mechanisms related
to the function of the autonomic nervous system: the activation of
the hypothalamus, hypophysis, sympathetic nervous system and stress
hormone (e.g., catecholamines, cortisol) secretion.
The primary functions of the cardiorespiratory system are to provide
the body with oxygen (O2), nutrients, removal of carbon
dioxide (CO2) and other metabolic waste products, maintain
body temperature and acid-base balance, and the transportation of
hormones from the endocrine glands to their target organs (e.g.,
Guyton and Hall, 2000,
The cardiorespiratory system responds predictably to the increased
demand of exercise. It is directly proportional to the skeletal
muscle oxygen demands where oxygen uptake (VO2) increases
linearly with increasing rates of work (e.g., McArdle et al., 2000,
p. 290-291). The intensity of exercise can be evaluated by recording
the heart rate (HR) (Gilman, 1996).
Calculating the average HR and comparing this to both the maximum
HR (HRmax) and the HR at rest (HRBasal), the
relative HR of the workload can be calculated (Karvonen and Vuorimaa,
Oxygen uptake (VO2, ml·min-1) during walking
with centrally carried load and heavy footwear has been calculated
for men as follows:
VO2 = 4.1mb + 0.367(mb + mload)·v2
+ 2.017mshoe·v2 (Holewijn et al., 1992)
where mb is body mass (kg), mload is mass of centrally
carried load (kg), mshoe is shoe mass (kg), v is walking
Autonomic nervous system
The autonomic system operates at a subconscious level and controls
many of the internal organ's functions, including the pumping activity
of the heart, movements of the gastrointestinal tract, and glandular
secretion (e.g., Guyton and Hall, 2000,
Reduced basal (morning) heart rate is a classic effect of functional
adaptation to endurance exercise training (e.g., McArdle et al.,
2000, p. 200, 370). On the contrary,
elevated morning heart rate may be accompanied in overreaching and
may reflect an early stage in the development of the overtraining
state (Dressendorfer et al., 1985; Kuipers and Keizer, 1988; Dressendorfer et al., 2000).
At rest, the HR depends on complex neurohumoural interactions (Dressendorfer
et al., 1985): afferent nerve traffic from specialized receptors
sensitive to pressure, volume, or chemical changes in the heart,
blood vessels, lungs or kidneys; reflex and tonic discharge of cardiovascular
centers in the brain stem that receive incoming afferent impulses
and higher commands from the hypothalamus and cerebral cortex; the
balance of efferent impulses in sympathetic (adrenergic) and parasympathetic
(cholinergic) nerve fibers to the cardiac pacemaker; activity of
beta-adrenergic and cholinergic membrane receptor sites; the influence
of circulating catecholamines; and the intrinsic rate of pacemaker
discharge. In addition, local temperature and pH, substrate utilization
for energy metabolism could modify heart rate (Roussel and Buguet,
1982; Dressendorfer et al., 1985).
The initial changes in HR after standing up are solely mediated
by withdrawal of vagal tone (Ewing et al., 1980).
The musculoskeletal system consists of the peripheral parts of the
motor system and comprises muscle and the connective tissue elements
that form the skeleton (e.g., Enoka, 1994, p. 241). Its primary purpose is to define and move
the body. To provide efficient and effective force, muscle adapts
to demands. In response to demand, it changes its ability to extract
oxygen, choose energy sources, and rid itself of waste products.
The prolonged and strong contraction of a muscle leads to the state
of muscle fatigue ("nutrient fatigue"), which is almost
in direct proportion to the rate of muscle glycogen depletion (e.g.,
McArdle et al., 1991, p. 377; Guyton and Hall, 2000, p. 77). Therefore, most muscle
fatigue results simply from an inability of the contractile and
metabolic processes of the muscle fibers to continue supplying the
same work output. However, the transmission of the nerve signal
through the neuromuscular junction can diminish after intense prolonged
muscle activity, thus further reducing muscle contraction ("neural
fatigue" e.g., McArdle et al., 1991, 377; Guyton and Hall, 2000,
p. 77). As muscle function becomes impaired during prolonged submaximal
exercise, additional motor-unit recruitment takes place to maintain
the required force output for the particular activity (e.g., McArdle
et al., 1991,
Strenuous physical activity can have diverse effects on muscle,
ranging from the subcellular damage of muscle fibers to stretch-
induced injuries (strains). The subcellular damage frequently produces
an inflammatory response and is associated with muscle soreness
that begins hours after the exercise has been completed (delayed
onset muscle soreness, DOMS). In contrast, strain injuries typically
occur as an acute painful injury during high-power tasks and require
clinical intervention (e.g., Enoka, 1994, p. 277-278).
Delayed onset muscle soreness is characterized by tenderness, stiffness
and pain in the exercised muscles, decreased flexibility, and impaired
neuromuscular performance as well as muscle oedema (e.g. , Armstrong,
1984; Cleak &
DOMS is often observed in subjects unaccustomed to exercise (Ebbeling
and Clarkson, 1989; Appell et al., 1992;
Kuipers, 1994) or related to unusually prolonged
or strenuous (Dressendorfer and Wade, 1983; Miles & Clarkson, 1994)
exertion. Although after four days of 187% increased cycling training
load the muscle soreness level was not changed (Filaire et al.,
2002). The idea that an unusual increase in physical
activity may be associated with muscle tissue damage prevails widely
(e.g., Koplan et al., 1982; Dressendorfer et al., 1991). For example, a marathon
run can cause an acute loss of muscle function (Sherman et al.,
1984; Nicol et
al., 1991a; 1991b;
Kyröläinen et al., 2000) and increased turgidity may be found as a symptom
of overreaching or short-term overtraining (Kuipers and Keizer,
1988). A sensation
of discomfort in skeletal muscles is most evidenced one to two days
following exercise (MacIntyre et al., 1995).
The endocrine system integrates physiological responses and plays
an important role in maintaining homeostatic conditions at rest
and during exercise (e.g., Guyton and Hall, 2000, p. 5, 836). Major endocrine organs are the pituitary,
thyroid, parathyroid, adrenal, pineal, and thymus glands. Several
other body organs contain discrete areas of endocrine tissue, which
also produce hormones. These include the pancreas, gonads, and hypothalamus
(e.g., McArdle et al., 1991, p. 384). Secretion of hormones
rarely occurs at a constant rate. It must be adjusted rapidly to
meet the immediate demands of the changing bodily function. The
concentration of a particular hormone in the blood is a function
of the quantity of hormone synthesized in the host gland and the
amount released into the blood. For a short period, it is possible
for hormone release to exceed its synthesis. The plasma concentration
of a hormone is referred to as the "secreted amount".
In most cases, the rate of removal is measured in the urine and
it is equal to the rate of release (e.g., McArdle et al., 1991,
Endocrine glands are stimulated three ways: hormonally, humorally,
and neurally (e.g., McArdle et al., 1991, p. 388). Responses of circulating hormones to exercise
have been divided into three groups: fast, modest rate and delayed
responses (Viru, 1992). The fast response is characterized by a rapid
increase in the concentration of hormones in blood plasma within
the first few minutes of exercise. Modest responses are characterized
by a gradual increase in the hormone concentration, which may continue
up till the end of the exercise or longer. On the other hand, a
gradual increase during the first period of exercise may be followed
by a levelling-off towards a constant level or by a declining trend
in the hormone concentration (Viru, 1992). The mechanism by which
the endocrine function is rapidly activated is connected with the
functions of nervous centers and a high rate of transfer of the
nervous influences to the endocrine glands.
In response to an episode of exercise, many hormones, such as catecholamines,
are secreted at an increased rate (Richter, 1986; U.S. Department of Health
And Human Services, 1996). This secretion is related
to the cardiovascular and metabolic adjustments of the working tissues.
The increase of epinephrine output is related to the intensity of
effort and causes the constriction of essentially all of the blood.
It also causes the increased activity of the heart, and the inhibition
of the gastrointestinal tract (e.g., Guyton and Hall, 2000, p. 703).
The central nervous system (CNS) maintains and regulates cortisol
production and secretion through the hypothalamus-pituitary-adrenal
axis. Cortisol is secreted in bursts, which are superimposed on
a circadian rhythm that has its peak in the early morning hours
and its nadir at the initial stages of sleep (Kuhn, 1989). The response of cortisol to physical exercise
is caused by a rise in adrenocorticotropic hormone (ACTH) (Schwartz
and Kindermann, 1990) and is best seen 20 to 30 minutes after the stimulus
(Kuhn, 1989). Another theory for the exercise induced changes
in serum cortisol was proposed by Galbo (1981)
who concluded that it is removed from plasma at higher rates during
work loads below 50% of maximal oxygen uptake (VO2max)
than at rest. In a study by Duclos et al. (1997)
neither brief nor prolonged light exercise induced any significant
variation in plasma ACTH or cortisol concentrations. Plasma ACTH
and cortisol concentrations increased only, if the exercise was
intense and prolonged. The training factor did not modify the intensity
or duration thresholds for the activation of the pituitary-adrenocortical
response to exercise. Pestell et al. (1989)
have found as a model of chronic physical stress, a significantly
altered baseline hormonal state as reflected in the primary mediators
of the stress response, the catecholamines and the hypothalamic-pituitary-adrenal
axis. Their response to severe exercise is distinct from that of
untrained individuals in whom conjugated catecholamines decrease
and ACTH increase. This may represent hormonal adaptation to prolonged
After four days of 187% increased cycling training load the testosterone
cortisol ratio decreased, and returned to the control level within
48 h of recovery (Filaire et al., 2002). During three weeks of continuous
intense cycling competition both testosterone and cortisol decreased
(Fernįndez-Garcia et al., 2002). However, no change was detected in serum gonadotropins
using the radioimmunometric assay (RIA), a far less sensitive method
for detecting very low concentrations of gonadotropins than the
immunofluorometric assay (IFMA) (Jaakkola et al., 1990;
Huhtaniemi et al., 1992; Lucia et al., 2001).
Exercise-induced changes in testosterone concentration can be caused
by a change in the production rate and altered binding or change
in clearance (Tremblay et al., 1995). Several other mechanisms (haemoconcentration,
decreased hepatic blood flow) could be involved, as well (Tremblay
et al., 1995). During prolonged exercise, changes in serum testosterone
concentration may be caused by direct testicular suppression or
mediated through the hypothalamus-pituitary level (Aakvaag et al.,
1978b). Tanaka et al. (1986)
concluded that the cause is reduced testosterone secretion, which
occurs in spite of increased stimulation of the hypothalamic-pituitary
Psychological responses to prolonged exercise
Mood is an enduring but not permanent emotional predisposition to
feel (International dictionary of medicine and biology in three
volumes, 1986, p. 1800) and react or
behave in a certain way (Sutherland 1989,
The "feel better" phenomenon after exercise (e. g., Leith,
1994, p. 135)
is often quoted, and a large body of research have demonstrated
a positive link between exercise and affective states. Mood improvements
following acute and chronic bouts of exercise have been reported
(e. g., Raglin, 1990), but controversial results have been found, for
example, when endurance athletes undergo intensified programs of
heavy training. After three days of increased swimming training,
mood disturbance increased (Morgan et al., 1988; O'Connor et al., 1991),
but there was no significant mood response to four days 187% increased
cycling training load (Filaire et al., 2002).
The mood of the experienced cadets before a ranger training course
was already reduced before the first day, which indicates the anxious
anticipation before the start of a very strenuous course (Opstad
et al., 1978).
Walking as an exercise mode
Walking is a comfortable exercise type for all adults, and it does
not require special facilities or exercise equipment, except shoes.
Walking campaigns (e.g., Ståhl and Laukkanen, 2000,
p. 35-36) have been arranged to get people involved in physical
activity. Walking is moving in such a way that the full body-mass
has alternate permanent contact with the ground, via the right and
left foot. It is a rhythmic, aerobic activity involving large muscle
groups, confering several benefits for fitness and health with minimal
adverse effects (Morris and Hardman, 1997).
In 1997 68% of the Finnish population was involved in walking whereas
the EU average was 31% (de Almeida et al., 1999).
In 2001-2002 there were almost two million active walkers in Finland
(Suuri kansallinen liikuntatutkimus 2001 - 2002, 2002,
There are several types of walking (Ståhl and Laukkanen, 2000,
p. 5). Soldier's rhythmic walking is marching. Wandering in nature
is called hiking. Load carriage by backpack is common with these.
Pace walking is a walking pattern where the pace varies from slow
to fast, as in interval type training. Power walking has been developed
to increase the intensity of walking by adding weights to the hands,
wrists, ankles, and torso. Arms are kept at a 90-degree angle. Fitness
walking and health walking both refer to a walking programme designed
to enhance fitness or health. Nordic walking exercise uses lightweight
walking poles, similar to those used in cross-country skiing, to
balance and make walking a more effective total body activity. Snowshoe
walking with poles is a popular alternative for those willing to
exercise in natural surroundings during the winter (Ståhl and Laukkanen,
2000, p. 5).
In research, walking has been included e.g., in weight maintenance
and weight reduction programmes (e.g., Fogelholm et al., 2000), and in studies on biochemical
risk factors for ischaemic heart disease (e.g., Huttunen et al.,
1979; Griffin et al., 1988). In several epidemiological
studies (e.g., Manson et al., 1999) brisk walking has been associated
with reduction in the incidence of coronary heart disease among
women. In a golf study (Parkkari et al., 2000) regular walking had many
positive effects on the health and fitness of sedentary middle-aged
men. Golf players were characterised to have high adherence and
low risk of injury and therefore walking was considered a form of
health-enhancing physical activity (Parkkari et al., 2000).
Cross-country skiing as an exercise mode
Cross-country skiing combines the actions of the arms and legs,
which has been proclaimed as one of the best overall aerobic exercises.
It can be performed using different techniques (e.g. classical and
free) (Eisenman et al., 1989). There were 732,000 skiers in Finland in 2001-2002.
Skiing ranked the third when compared to the volume of participants
in other types of activities (Suuri kansallinen liikuntatutkimus
2001 - 2002, 2002,
Classical technique involves the same rhythmic arm and leg movements
observed in walking. The most common classical technique is diagonal
striding. This style consists of alternating arms and legs in a
rhythmic fashion. As a pole is planted, the opposite leg pushes
off. In some terrain conditions higher velocity can be achieved
using a single kick, double pole variation, where a double poling
motion uses both arms to push off simultaneously. A skier can also
double pole without a kick. The classical technique incorporates
a kick, glide and poling phase, which are repeated. The ability
to diagonal stride depends upon technical skill, the ability to
work at a high percentage of VO2max, economy of motion,
and a myriad of motivational factors. Effective classic technique
necessitates sufficient leg strength and balance to permit the weight
to be supported on one leg during the glide, but the actual strength
required is not great. (Eisenman et al., 1989; Smith, 2002).
The two oldest freestyle techniques are the marathon and V-skate.
They incorporate a lateral pushing action with one ski while the
opposite ski maintains a forward glide. In marathon skate style
one ski always remains on the track while the other ski continuously
pushes off with a double-poling action. This style requires classical
tracks, which are not needed in the V-skate. During the V-skate
the legs alternate from side to side with lateral strokes. Double-poling
every other or every kick, and no poling can be used (Eisenman et
al., 1989; Smith,
In cross-country skiing, fatigue may be caused by energy depletion,
metabolite accumulation, inadequate oxygen delivery or disturbances
of homeostatic functions, or it may be of neuromuscular origin (Rusko,
2003a). During prolonged skiing (5-11 h) the measured
mean heart rate levels were 134-165 beats·min-1 (Vuori,
1972). It represented the level
of 80 to 91% of the individual maximal heart rate of subjects. Muscle
enzyme (CK) activities after 42 to 90 km of skiing were minor in
subjects under 30 years, but there was found to be a significant
increase in men over 50 years (Vuori, 1972).
Studies of daily repeated prolonged exertions with men in field
Due to the practical and theoretical interest to understand the
effects of repeated exertions several studies (Table
1) have focused on daily repeated walking exercise with men
in field conditions. However, all of these studies extended only
a limited point of view, e.g., concentration on a few specific physiological
variables. Walking distances have varied from 35 to 630 km and follow-up
time from two to 42 days. The number of the subjects has varied
between 1 to 97 and the oldest subjects have been over 70 years
Shapiro et al. (1973)
studied the relationship between maximal aerobic capacity and changes
in blood enzyme concentrations (creatine phosphokinase, glutamic
-oxaloacetetic transaminase, aldolase, creatine, creatinine and
sorbitol dehydrogenase) in 26 untrained subjects during a 110 km
2-day march. The highest enzyme elevation appeared in subjects with
the lowest maximal aerobic capacity and a moderate elevation in
those with high maximal aerobic capacity, and it was suggested (Shapiro
et al., 1973) that enzyme elevations were
primary related to the intensity of the effort with respect of VO2max
of the individual and not to its duration.
Myles et al. (1979) studied 25 infantry soldiers
who marched 204 km in six days. The daily walking distances were
34, 34, 34, 30, 30.5, and 38.5 km at an average speed of 6 km·h-1
on the first day and at 6. 5 km·h-1 over the next 5 days.
An additional weight (22 to 24 kg) was assigned to each subject
to ensure that all worked at the same percentage of his aerobic
power (40%). The factor limiting performance for many of the subjects
was the condition of their feet as a result of marching on the hard
road surfaces (Myles et al., 1979).
Roussel and Buguet (1982)
examined the effect of six days of moderate prolonged exercise on
nighttime heart rates during sleep in four fit, healthy young men.
The length of the march was 34 km·day-1 and the speed
was 6 km·h-1, with an intensity of 35% of individual
VO2max. After the exercise period the nighttime heart
rates increased by about 10% as compared to the previous control
condition, and returned to normal during the five days' recovery
period. The increase was apparently not related to changes in body
temperature, red blood cell content, sleep patterns, cortical adrenal
or thyroid functions. The most likely explanation for the nocturnal
tachycardia was related to a probable increased sympathoadrenal
activity (Roussel and Buguet, 1982).
In a study by Ross et al. (1983)
after one day of severe exercise (not detailed) and two days' walking
(15 and 20 km, respectively) serum creatine kinase concentration
was seven times higher than the rest level before the exercise.
Davies et al. (1984)
studied one male subject during 338 miles (130 h) of continuous
walking and subsequent sleep deprivation. Creatine kinase and its
isoenzyme levels rose throughout the walk. Catecholamine levels
rose throughout the walk, with lager increases being observed in
noradrenaline and dopamine. During the post-walk recovery phase,
adrenaline concentration remained elevated (Davies et al., 1984).
In a study by Marniemi et al. (1984) ten men hiked 344 km from Jyväskylä to Helsinki
over seven days. The daily walking distances were from 36 to 67
km at an average speed of 3.5 km·h-1. Estimated energy
consumption corresponded to 3.5 kcal·min-1 yielding in
total about 84 MJ (20 Mcal). During the exercise men were allowed
to drink water, mineral drinks, and juices ad libitum. Except for
some natural products, no food intake was allowed. Total caloric
intake during the hike was about 24 MJ (5,700 kcal) and the sleeping
time was 5 h·night-1. The body mass and serum protein
concentrations of the subjects decreased by about 7%, on average.
Serum cortisol in the evening after the daily hiking and plasma
noradrenaline concentrations were significantly increased and serum
testosterone levels decreased, reflecting the immediate daily response
to the combined fasting and hiking. Hormonal stress adaptation was
reached in three days. Decreased testosterone levels indicated the
involvement of the LH- testis pathway (Marniemi et al., 1984).
Greenhaff et al. (1987),
Maughan et al. (1987),
and Griffin et al. (1988)
studied the metabolic responses to prolonged walking on four consecutive
days in fed and fasted men. Six healthy men walked 37 km per day
on two occasions one month apart; during one walk they consumed
a high carbohydrate (CHO) diet and during the other walk an isocaloric
low CHO diet. Each day's walking accounted for about 50% of total
energy expenditure and the workload was equivalent to 17±1% of VO2max.
The first day of each walk demonstrated that the pattern of substrate
mobilisation in response to this type of exercise is highly reproducible.
Circulating glucose, lactate, insulin, and triglyceride concentrations
remained essentially unchanged; alanine fell progressively and glycerol,
free fatty acids and 3-hydroxybutyrate rose progressively. Very
low-density lipoprotein cholesterol decreased and high-density cholesterol
increased when the subjects consumed a mixed diet. The results indicated
that even in the overnight fasted state, substrate mobilisation
during prolonged low intensity exercise is markedly influenced by
the composition of the preceding diet.
studied the treatment of feet abrasions with a hydrocolloid dressing
in a military unit during intensive marching. Abrasions were mostly
(54%) located in the heel region, under the front foot pad (19%),
on the sides of the food (14%), and on the toes (10%). After treatment,
pain relief was good in 92% and moderate in 8% of those who initially
had severe (28%) or moderate (64%) pain.
Faber et al. (1992)
studied the effect of prolonged low intensity hiking over a period
of six weeks on plasma lipids in 11 men. The subjects walked an
average of 15 km per day including resting days. They completed
a seven-day estimated dietary record before and during the expedition.
The authors concluded that increased physical activity during a
hiking expedition together with drastic dietary changes (less protein
and fat, and more carbohydrates as compared to their habitual intake)
and weight loss (73.8 to 68.2 kg) result in significant decrease
in mean plasma total cholesterol level (Faber et al., 1992).
Hellsten et al. (1996)
investigated the effect of seven days of strenuous (150 km) marching
exercise on xanthine oxidase and insulin-like growth factor in skeletal
muscles in 15 men. They observed an elevated expression of xanthine
oxidase, insulin-like growth factor immunoreactivity and plasma
creatine kinase activity after the exercise. They suggested that
the increases resulted from cellular damage.
De Wild et al. (1997)
studied 97 men over 70 years old who completed the 1993 Nijmegen
Four-Day long-distance March (30 km·day-1 on four consecutive
days). The mean velocity was 5 km·h-1, mean relative
exercise intensity was 52% of VO2max and average heart
rate 70% of HRmax. VO2max was the most important
predictor of the variance in self-selected velocity.
Cross country skiing studies
There are only three studies of daily repeated prolonged skiing
exertions with men in field conditions (Table
Vuori et al. (1979)
studied plasma catecholamine concentrations and their responses
to short-term physical exercise during and after a six-day ski-hike.
has reviewed the findings from the 91 days transpolar ski-trac,
which are described also in Aidaraliyev and Maximov's (1990),
Booth et al.'s (1990),
and Panin's (1990)
proceedings. Fellmann et al. (1992)
investigated the interrelationships between pituitary-adrenal hormones
and catecholamines during a 6-day Nordic ski race at 1,120-1,230
m above sea level. They obtained the blood samples before and after
each day's racing.
In the study of Vuori et al. (1979)
the basal noradrenaline plasma levels were increased during the
first days of a ski-hike. However, in four days, a plateau was reached.
The fluctuations in adrenaline concentrations were in the same direction,
although not as striking as those in noradrenaline. Changes in dopamine
concentrations were negligible.
In Shephard's study (1991)
strength increased, body fat decreased by 5% and aerobic power showed
an anomalous decline over the transpolar ski-trek.
Fellmann et al. (1992)
found different control mechanisms for hormones of the pituitary-adrenal
axis and catecholamines.
Most of the studies about the responses to daily repeated prolonged
exercise during a specific effort concern running (Table
3), however, none of them focus on mood.
Sanders and Bloor (1975)
measured heart rate, rectal temperature, haematocrit, plasma hemoglobin,
creatine phosphokinase (CPK), glutamic-oxaloacetatic and glutamic-pyruvic
transaminases, lactate dehydrogenase (LDH), adenylate kinase (AK),
and lactate and pyruvate before and after exercise during five consecutive
days of distance running. Significant increases in heart rate and
rectal temperature were unrelated to enzyme levels. Pre-exercise
CPK levels rose progressively during the five days exercise period
and post-exercise levels were significantly greater than pre-exercise
levels on each running day but were unrelated to the severity of
the exercise. LDH and AK levels did not change with the exercise
stress. They (Sanders and Bloor, 1975)
suggest that CPK is a sensitive index of exercise stress in well-
conditioned runners and elevated CPK and AK levels in such a runners
represent physiological responses.
Dressendorfer et al. (1981),
Wade et al. (1981),
Dressendorfer et al. (1982;
1985), and Dressendorfer
and Wade (1983)
have studied marathon runners during a 20-day Great Hawaiian Footrace
on days 2, 5, 8, 13, 14, 17, and 20. The participants ran every
day, except for a 70-hour rest period following the run on the tenth
day till the morning of the 13th day. Dressendorfer et al. (1981)
found decreased red blood cell counts and haemoglobin levels after
long-distance running that they called "sport anemia".
Wade et al. (1981) studied the renal function, aldosterone, and
vasopressin excretion and their data suggested that in response
to repeated long-distance running normal fluid balance is regained
within 12 hours. Dressendorfer et al. (1982)
measured the plasma mineral levels and found no tendency of persistent
reduction over the 20 day period. Wade et al. (1982)
found no urinary abnormalities (proteinuria, haematouria or cylinduria)
during the Great Hawaiian Footrace. Dressendorfer and Wade (1983)
measured indicators of muscular injury during the race and found
elevated serum creatine kinase levels, mild-to-moderate thigh muscle
soreness or stiffness, and reduced thigh circumference. Dressendorfer
et al. (1985)
found slightly reduced morning heart rates after the first week
of running but thereafter morning heart rates increased progressively.
Blood pressure, oral temperature, body weight, sweat loss, and blood
glucose, lactate, insulin levels, and cortisol levels were not related
to the increase in morning heart rate.
The impact of a 20-day run (from the Baltic Sea to the Alps) on
pituitary, testicular, adrenal and thyroid hormones has been investigated
on the first, fifth, ninth, 14th and 19th day (Schürmeyer et al.,
1984). Results showed that adrenal and thyroid function
soon adapted to the daily strain. Testosterone levels were markedly
decreased throughout the 20 days while LH levels remained unchanged.
Pestell et al. (1989)
have studied the biochemical and hormonal responses to a 1,000 km
ultra marathon. They analysed serum catecholamine, cortisol, and
adrenocorticotrophic and growth hormone (GH) levels after the eight
day race and found a significant increase in cortisol, prolactin
Dressendorfer and Wade (1991)
studied the effects of a 15-day race around the Hawaiian islands
of Oahu and Maui. Race distances varied from 15 to 34 km, averaging
26.7 km·day-1. Plasma testosterone, adrenal steroid and
cortisol levels were measured, and four field tests for leg muscle
fitness were used. Testosterone decreased 31% and the ratio of cortisol
to testosterone 83% but the test scores for leg power did not change.
Dressendorfer et al. (1991)
examined the effects of 7 consecutive days of prolonged running
on aerobic performance and biochemical markers of muscle and red
blood cell damage in moderately fit men, who jogged for 2 h·day-1;
nearly eight times their regular weekly training volume. All subjects
experienced leg muscle soreness, especially in the thigh region,
after three days until the end of the race. There was a 6-fold elevation
in serum enzyme (CK, myoglobin) levels after the fifth day.
Raschka et al. (1994a; 1994b),
and Raschka et al. (1995)
examined the changes of hormone, and serum enzyme values during
an ultra long distance run of 1,000 km. They found decreased insulin,
FSH and LH concentrations after the exercise (Raschka et al., 1994a; Raschka et al. , 1995).
The highest enzyme activities were found after the third day (Raschka
et al., 1994b).
Höchli et al. (1995)
studied the loss of oxiadative capacity after an extreme endurance
Paris-Dakar foot-race. They took muscle biopsies from musculus vastus
lateralis before and after the race and analysed fiber size, capillarity
and muscle ultrastructual composition. Body fat, thigh cross-sectional
area and thigh volume showed tendential reduction immediately after
the race. Fiber size and capillarity were not affected by the race.
Volume density of total mitochondria, and both subsarcolemmal and
interfibrillar mitochondria were reduced.
Oksa et al. (1995)
recorded the heart rates of seven males participating in a 5 day
jogging relay. The jogging speed was controlled at 3.0 m·s-1
on average. During the relay the mean heart rate values were 150
beats·min-1, corresponding to 68% VO2max.
The jogging time above anaerobic threshold heart rate level was
9% of the total jogging time. The results indicated that even in
a leisure oriented jogging event, cardiorespiratory strain can be
Bishop and Fallon (1999)
documented injuries in 16 men during a 6-day track race and compared
these injuries with those incurred during other ultra-marathon track
and road races, and investigated a characteristic ultra-marathon
injury, tendonitis of the ankle dorsiflexors. They reported a total
of 36 injuries in 11 competitors. The ankle and knee were the regions
most frequently injured and the most common diagnosis was Achilles
tendonitis. During the same ultra long distance running Fallon and
studied the changes in erythropoiesis. There were findings of hemodilution
but red cell parameters were relatively unchanged.
In all studies of daily repeated prolonged cycling exertions with
men in field conditions (Table
4.) the subjects were elite cyclists and in only one study the
measurements had been done daily containing only heart rate measurements.
Saris et al. (1989a)
looked at food intake and energy expenditure while Saris et al.
the adequacy of vitamin supply during the Tour de France. Energy
expenditure values of the cyclists ranged from a mean of 25.4 MJ·day-1
to peak values of 32.7 MJ·day-1. The contribution of
macronutrients to energy intake was: 62% from carbohydrates, 23%
from protein and 15% from fat. No changes over the 22-day period
were observed in mineral or vitamin parameters.
Palmer et al. (1994)
and Lucia et al. (1999)
have monitored heart rate responses during cycling races. On consecutive
days Palmer et al. 's (1994)
subjects competed in a 16 km individual time trail, a 110 km mass-start
road race, a 5.5 km individual hill climb, and a 105 km mass-start
road race. Despite similar racing speeds, the heart rate responses
to the longer mass-start races were reduced. Lucia et al. (1999)
evaluated the heart rate response to professional road cycling during
a 3-week Tour de France (4 400 km) competition as an indicator of
exercise intensity. They used two reference heart rates (corresponding
to the first and second ventilatory thresholds) to establish three
phases of exercise intensity. The relative contributions of each
phase were 70%, 23%, and 7%.
Lucia et al. (2001),
Fernįndez-Garcia et al. (2002),
and Filaire et al. (2002)
have evaluated the hormonal responses during cycling races. Lucia
et al. (2001)
measured morning urinary levels of 6-sulphatoxymelatonin, and morning
serum levels of testosterone, follicle stimulating hormone, luteinizing
hormone, and cortisol before the competition, and at the end of
each week during the three weeks Tour de France. Urine samples were
also evaluated in the evening at the end of each of the three weeks.
They found decreased 6-sulphatoxymelatonin, cortisol and testosterone
levels after consecutive days of intense, long-term exercise.
Fernįndez-Garcia et al. (2002)
studied the response of sexual and stress hormones of male professional
cyclists during the three weeks of Vuelta a Espańa. They found a
decrease in the plasma testosterone and cortisol, but no changes
in LH or FSH during the race.
Filaire et al. (2002)
measured hormones during the four days of increased training (+187%)
in cyclists. They assessed the overall mood and muscle soreness
levels, as well. A decrease in testosterone and an increase in cortisol
levels were observed but the overall mood and muscle soreness were
not affected by the training.
Table 5 provides a summary
of the studies of daily repeated prolonged swimming exertions with
men in field conditions.
Kirwan et al. (1988)
examined physiological responses to ten successive days of intensive
training in competitive swimmers. Morning resting heart rates, and
blood pressure were measured daily. Cortisol, catecholamines, creatine
kinase, glucose, lactate and plasma volume were determined in the
beginning, middle and at the end of the training period. Serum cortisol
and creatine kinase were elevated, haemoglobin and haematocrit increased,
with no other significant changes observed.
Morgan et al. (1988)
studied 12 male swimmers psychologically before, during, and after
ten days of increased training. Daily training distance was increased
from 4,000 to 9,000 m·day-1, and intensity was maintained
at 94% of VO2max. They found significant increases in
the ratings of muscle soreness, depression, anger, fatigue, and
global mood disturbance, along with a reduction in the sense of
O'Connor et al. (1991)
studied the physiological effects of 3 days of increased training
in swimmers. Training volume of 22 male college swimmers was increased
from 8,800 to 12,950 m·day-1. Salivary cortisol, heart
rate, stroke mechanics, as well as overall and local ratings of
perceived exertion (RPE) were measured in conjunction with the two
swim tests. Mood states and ratings of perceived muscle soreness
were assessed daily. Elevations of fatigue, mood state data, and
muscle soreness levels occurred in association with the increased
All studies (Table 6), where
the responses to prolonged physical strain during military training
courses have been followed, include sleep deprivation or low energy
diet, or both.
Aakvaag et al. studied the effect of prolonged physical and psychological
stress on the testicular function during a combat course; high caloric
consumption with limited caloric intake, lack of sleep, strong discipline
with occasional irrational punishment (1978a),
and the endocrine response (1978b).
They found a marked suppressive effect on plasma testosterone and
no changes in LH or FSH levels.
Opstad et al. (1978)
studied the shooting, command memory and reaction time task, visual
vigilance, code and sorting test, and mood in men exposed to prolonged,
severe physical work and sleep deprivation during four and five
day combat courses. The subjects were tested and clinically examined
each morning. They observed substantial impairment in all tests,
as well as clinical symptoms toward the end of the courses.
Opstad and Aakvaag (1982),
and Opstad (1994)
studied the hormonal responses during military training course involving
heavy and continuous physical activities with almost total lack
of food (less than 1,500 kcal·day-1) and sleep. Testosterone
(Opstad, 1994; Opstad and Aakvaag, 1982)
was strongly reduced and cortisol increased (Opstad, 1994) during the course. Opstad
(1994) investigated the mental
performance, as well, which decreased.
AIMS OF THE STUDY
aim of this work was to examine the magnitudes and time courses of
the physiological and psychological responses to various (intensity,
duration, mode/type) daily repeated prolonged exercise. The specific
problems were to describe in healthy men the responses of the cardiovascular
(Study 1, 3, 5), autonomic nervous (Study 3, 5), musculoskeletal (Study
1, 3, 5), and endocrine systems (Study 1, 2, 4, 6), and mood states
(Study 2, 3, 5).
The focus was on the quantification of possible disadvantages caused
by daily repeated physical activity differing in intensity, duration
Acute cardiorespiratory response was measured by the heart rate during
the exercise. Responses of the autonomic nervous system were estimated
by measuring the heart rates in an orthostatic test. Musculoskeletal
responses were estimated by measuring the perceived pains, flexibility,
functional strength, use of elastic energy and oedemic changes of
the lower extremities. Hormonal responses were assessed using the
urinary excretion of catecholamines, and serum cortisol, testosterone
and gonadotropins. The mood state was evaluated using the Profile
of Mood States (POMS) test.
The hypothesis of this study was that prolonged strenuous exercise
would decrease the functional capacity of the lower extremities, disturb
the balance of the autonomic nervous system and the secretion of hormones
from the adrenal cortex and pituitary-testicular axis, also negative
mood states were postulated.
A total of 28 healthy physically active fit men volunteered for
these studies after they had been fully informed and their signed
informed consent was obtained. Three of the subjects were involved
in two different study designs (Study 3-4 and 5-6). In the first
marching studies (Study 1-2) the subjects were army officers representing
the Finnish Military Sports Federation. In the two other marching
studies (Study 3-4) nine subjects were army officers representing
the Finnish Military Sports Federation and six were cadets from
National Defence College; First Degree Division (Military Academy,
In the skiing studies (Study 5-6) the subjects were three army officers
and seven recreational endurance athletes. None of the subjects
were taking any prescribed medication or had a history of cardiovascular,
renal or skeletal muscle diseases. Their level of physical fitness
was high and body mass was in normal proportion to their height,
and they had relatively low subcutaneous fat content. The subjects
of studies 1-2 had, preceding the march, 10 weeks of a common preparatory
training program consisting of an average of 9.3h of exercise during
2 to 4 h sessions, and their training background was 414 ± 197 h·year-1.
This training amount did not differ from their habitual physical
activity and it was performed almost solely by walking. The subjects
of studies 3-6 had no specific preparatory training program for
the events. Some physical characteristics of the subjects are summarized
in Table 7.
The data of these short-term follow-up (reversal) designs (Cook
and Campbell, 1979;
Thomas and Nelson 1990,
p. 311-313) were collected in 1993 (Study 1, 2) and 1994 (Study
3, 4) during the "International Four-Day Long- Distance March"
in Nijmegen, The Netherlands, and in 1995 during the Finlandia Ski
Race (Study 5, 6). The track profile of the Finlandia Ski Race is
presented in Figure 1.
Characteristics of the events are summarised in Table
8. The Ethics Committee of the University of Jyväskylä, Finland
and the Defence Staff, Finnish Defence Forces, Department of the
Health Care approved the arrangements of this study.
The "International Four-Day Long-Distance March" in Nijmegen,
The Netherlands is open to both civilian and military participants
who march over 40 km on each of the four days. Walking during the
march was determined as follows: "moving forward in such a
way that the full body-weight has permanent contact with the ground,
alternately via the right and the left feet" (Program- Magazine
De 4 Daagse, 1994).
As the intention of the march was not to cover the total distance
within the shortest possible time, the competitive element can be
considered to be minimal. Detachments marched together, two abreast.
In order to avoid dehydration and energy deficit, water and standard
food (soup, meat, potatoes, bread, salad, dessert) were provided.
At the three main resting stops soft drinks, milk and snacks were
for sale. The surface of the routes was mostly hard (asphalt or
stone) and the route was almost totally flat, except on the third
day. The average air temperature during the marches in 1993 almost
totally flat, except on the third day. The average air temperature
during the marches in 1993 and 1994 was 12 to 15°C early in the
morning and 18 to 30°C at noon. The subjects wore ordinary army
uniforms and combat boots (1,400 g). The last 10-km of the fourth
day march was walked without the backpack because of the final parade.
The walkers were required to carry a backpack weighing at least
10 kg. Apart from the participants, only one support person on bicycle
was permitted per detachment. Night rest in tents commenced between
08.00 - 10.00 p.m., and ranged from 5 to 7 h in length. Consumption
of food and beverages was not limited. Medical care was provided
through subjects' self-medication and by the organizers. No exercise
was performed two days before, or one week after the march.
In studies 5-6 the distance skied daily was 50 km on both days,
starting at 11:00 a.m. On the first day the skiing technique to
be used was classical and on the second free. The weather conditions
were similar on both days: air temperature +1°C and cloudy. In order
to avoid dehydration effects and an energy deficit, water and small
snacks were provided during the event. One of the subjects (n=10)
had to leave the study because of a fall.
The protocol of the physiological measurements and collections are
shown in Tables 9, 10,
11. The measurements consisted
of body mass, heart rate during the exercises, orthostatic test,
perceived pain and functional capacity of lower extremities. Blood
samples were also taken and urine was collected during the study.
The mood state was evaluated using the Profile of Mood States (POMS)
test (McNair et al., 1971).
The best result of subjects in the Cooper's 12-minute running test
(Cooper, 1968) within the last two years was used to evaluate
the endurance capacity of the subjects in studies 1-4. Maximal oxygen
uptake and the related variables were measured during an incremental
uphill walking test on a treadmill to subjective maximal effort
from seven subjects of the studies 3-4 and all subjects (n=10) of
studies 5-6. Expired air was collected and analysed continuously
with an automatic metabolic analyser (Beckmann MMC, Beckman Instruments,
Illinois, USA) for successive 30-second periods. The electrocardiogram
was monitored continuously and heart rate was recorded at the end
of each two-minute stage.
Body mass was measured, and the percentage of body fat was estimated
from the thickness of four skinfolds (Durnin and Rahaman, 1967). Body mass index (BMI) was
calculated according to the height and mass of the subjects (Keyes
et al., 1972).
Alcohol consumption and the use of analgesic drugs during the exercises
were questioned in studies 1-4.
Cardiorespiratory and autonomic nervous system
Each subject wore a heart rate monitor (Sport Tester PE 3000, Polar
Electro OY, Kempele, Finland). Heart rates were recorded at 60-s
intervals during the exercises. Orthostatic heart rate recordings
(Study 3, 5) were taken firstly in the supine position after the
night sleep and secondly at 30 seconds after getting up by a heart
rate monitor (Sport Tester PE 3000, Polar Electro OY, Kempele, Finland).
Heart rates were recorded at 15-s intervals.
Responses to the musculoskeletal system were evaluated by questions
on perceived pain, assessment of functional capacity of lower extremities
(the range of movement, muscle strength and the use of elastic energy,
circumferences), and measurements of creatine kinase activity (CK)
in serum (Study 1, 5).
Intensity of overall perceived pain was assessed using a visual
analogue scale (VAS) (Haynes and Perrin, 1992). The scale was a 10-cm horizontal line ranging
from "no pain" (on the far left) and "unbearable
pain" (on the extreme right). The following descriptors were
spread at even intervals along the line from left to right: "dull
ache", "slight pain", "more slight pain",
"painful", and "very painful". Pain was quantified
by measuring the length of the line from the extreme left of the
scale to the subject's mark. The location of pain in the lower limbs
(muscle, joint, feet) as well as other pains, abrasions and blisters
were indicated on body charts and pain intensity was estimated with
a score of descriptors ranged from 0 to 6 with terms alike in the
To assess the flexibility of the lower extremities, the range of
movement (ROM), was measured with a standard plastic goniometer
(Wang et al., 1993).
The subjects were instructed to relax the muscles during the procedure.
The tightness of the knee flexors (KF) was determined by passive
hip flexion with the knee extended. Subjects were positioned supine
on a table with their opposite thigh and the knee to be measured
stabilised. The goniometer was placed with the stationary arm parallel
to the midline of the trunk, the moving arm along the lateral midline
of the thigh, and the axis over the superior half of the greater
trochanter. The leg to be measured was raised to the point in the
range where a small amount of pelvic movement was elicited by the
investigator. The tightness of the knee extensors (KE) was measured
by hip extension. Subjects were positioned supine on the table with
the leg to be measured hanging over the table. The opposite hip
and knee were flexed to the point where the investigator palpated
that the subject's lumbar spine was flat on the table. The subjects
were instructed to maintain this hip and knee position with the
fingers of both hands interlocked over the anterior tibia to assist
in the maintenance of the posterior pelvic tilt. The goniometer
was placed with the stationary arm parallel to the lateral midline
of the thigh, the moving arm along the lateral midline of the tibia,
and the axis over the lateral side of the knee joint. The tightness
of the hip flexors (HF) was measured with the hip extended. The
procedure was the same as for the measurement of the knee extensors,
except that goniometer placement was the same as that for the measurement
of the knee flexors.
Functional muscle strength and the use of elastic energy of the
lower extremities were evaluated according to Komi and Bosco (1978)
on an electric contact mat (Digitest OY, Muurame, Finland) with
maximal voluntary vertical jumps. The first jump, called a squat
jump (SJ), was performed from a static semisquatting position (a
knee angle of 90 degrees) with no allowance for preparatory counter-movement.
In a second jump, called a counter-movement jump (CMJ), the subject
started from a standing position with a preliminary counter movement
followed by an immediate jump upwards. The isolated jumps (SJ, CMJ)
were repeated three times and the average flight time was calculated.
Oedemic changes of the lower extremities were estimated by measuring
the greatest circumference of the calves (CC), as well as circumference
of the thighs (CT) 25 cm above the middle part of the patella.
Urinary collection and catecholamine analyses
All daily urine was collected in study 1. Urine prior to the first
march, during each march and between the marches was collected separately.
Urinary volume and collection time were measured and used to estimate
urine excretion. Four ml of 6 M hydrochloric acid was added to the
urine to decrease pH, and the samples were kept frozen at -20°C
until assayed within six months at Department of Forensic Medicine,
University of Oulu. Urinary catecholamines were purified by an Al2O3-extraction
procedure. The catecholamines were extracted at a pH of 8.6 from
25 µl urine into 30 mg Al2O3 with 3.4 - dihydroxybenzylamine
hydrobromide as an internal standard. After washing four times with
2 ml H2O, the catecholamines were released into 100 µl
0.2 M HClO4 - solution. A high pressure liquid chromatograph
with an electrochemical detector (Esa Couluchem Multi- Electrode,
model 5100 A, ESA, Inc., Chelmsford, MA, USA) was used for the determination
of free noradrenaline and adrenaline. The column was an Esa Catecholamine
HR-80 and a mobile phase Esa Cat-A-Phase reagent. The flow rate
was 1.0 ml·min-1. The ratio of the peak height of each
catecholamine standard to the peak height of the internal standard
was used as the basis for concentration calculations.
Blood samples and biochemical analyses
In studies 1-2 blood samples were taken in the afternoon (between
1:30 and 5:30 p.m.), except PreI sample, which was taken in the
morning (between 2:00 and 4:30 a.m.). In studies 3-4 blood samples
were taken at 11 time points in time and in the same order with
respect to each subject on each day (variation ± 1 h), following
a systematic time pattern: 1) a day before the first exercise session
between 2:00 and 5:00 p.m. (0 sample), 2) in the morning (between
2:00 and 5:30 a.m.) within 2 hours preceding each walking session
(Study 1 - 4), 3) in the afternoon (between 2:30 and 6:30 p.m.)
within 60 min after each walking session, and 4) one and nine days
after the last day of the walk (between 7:00 and 8:00 a.m. and between
1:00 and 2:00 p.m., respectively). In studies 5-6 blood samples
were taken between 9:45 and 10:15 a.m. and between 1:30 and 3:00
p.m. after both event, and after one week's recovery at 2:00 p.m.
Blood was drawn from the antecubital vein. Serum was separated and
kept frozen at -20ŗC until assayed.
Serum creatine kinase (CK) activity (Study 1, 5) and total protein
concentration (Study 4, n=10) were analysed according to standard
laboratory methods: Serum creatine kinase (Boehringer, Mannheim,
Germany) and protein (Reagena, Kuopio, Finland) in LIKES-Research
Center, Jyväskylä. The normal value of CK provided by the kit manufacturer
for men was CK µ190 U·l-1.
Concentrations of serum cortisol and testosterone were measured
using radioimmunometric assay (RIA) kits purchased from Farmos Diagostica
(Turku and Oulunsalo, Finland) in LIKES-Research Center, Jyväskylä
(Study 1) and in Research Institute of Military Medicine, Helsinki
(Study 4, 6). Concentrations of serum immunofluorometric LH and
FSH were measured using time-resolved immunofluorometric assay (IFMA)
kits (DELFIA hLH Spec, DELFIA hFSH) provided by Wallac OY (Turku,
Finland) in Department of Physiology, University of Turku (Study
2, 4, 6). The intra- and inter-assay coefficients of variation were
below 5 and 10%, respectively. The reference ranges for men provided
by the kit manufacturer were as follows: cortisol 244 - 727 nmol·l-1
between 7:00 and 10:00 a.m. and 110 - 418 nmol·l-1 between
3:30 and 5:30 p.m., testosterone 9 - 38 nmol·l-1, LH
1.0 - 8.4 IU·l-1, and FSH 1.0 - 10.5 IU·l-1
In study 6 one subject with resting LH value lower than the reference
range was excluded when calculating the means of LH and the standard
deviations of the means.
Mood states were assessed with the Profile of Mood States (POMS)
questionnaire "How you have been feeling today?" (McNair
et al., 1971),
which measures six identifiable moods of affective states: Tension-Anxiety
(T), Depression-Dejection (D), Anger-Hostility (A), Vigour-Activity
(V), Fatigue-Inertia (F), and Confusion-Bewilderment (C). A total
mood disturbance (TMD) score was also obtained from the POMS by
summing the scores across all six factors (weighting V negatively),
and adding a constant of 100 to eliminate negative values. The higher
the TMD score, the worse is the mood. Possible ranges of the POMS
raw scores are as follows: Tension-Anxiety 0-36, Depression-Dejection
0-60, Anger-Hostility 0-44, Vigor-Activity 0-32, Fatigue-Inertia
and Confusion-Bewilderment 0-28. Factor T is defined by adjective
scales descriptive of heightened musculoskeletal tension. The defining
scales include reports of somatic tension, which may not be overtly
observable (Tense, On edge), as well as observable psychomotor manifestations
(Shaky, Restless). Factor D appears to represent a mood depression
accompanied by a sense of personal inadequacy. It is best defined
by scales indicating feelings of personal worthlessness (Unworthy),
futility regarding the struggle to adjust (Hopeless, Desperate),
a sense of emotional isolation from others (Blue, Lonely, Helpless,
Miserable), sadness (Sad, Unhappy), and guilt (Guilt, Sorry for
things done). Factor C appears to represent a mood of anger and
antipathy towards others. Factor V is defined by adjectives suggesting
a mood of vigorousness, ebullience, and high energy. It is negatively
related to the other POMS factors. Factor F represents a mood of
weariness, inertia, and low energy level and factor C appears to
be characterized by bewilderment and muddleheadness. In study 2
(n=5) mood states were measured one week prior and immediately before
the first march, within 1 hour after each march session. In study
3 (n=8) mood states were measured the day before the first march,
and during the evening of each day of marching and nine days after
the last march. In study 5 (n=6) mood states were measured one day
before the event, daily after the event, and after a one-week recovery
The results are presented as means (± SD or SE). Statistical analyses
were performed using the Statistical Package for Social Sciences
(SPSS, Version 9.0 for Windows, SPSS Inc., USA). A one-way ANOVA
with repeated measures was employed to examine the response to repeated
exercise. In the case of a significant repeated exercise response
in ANOVA, the other time points were compared to the baseline, further
analysis was then performed with the Student's t-test for matched-pairs.
A separate ANOVA for morning and afternoon hormone samples (Study
4) was used because of the circadian rhythm. An a priori p-value
of < 0.05 was selected to indicate statistical significance.
main findings from the experiments are presented below. For more
details consult the original papers (Study 1-6).
Physiological responses to daily repeated prolonged exercise
The average heart rate during walking was 109 ± 9 (Study 1-2) and
108 ± 6 (Study 3-4) while during skiing it was 157 ± 13 beats·min-1
(Study 5-6). The mean heart rate level during walking was 57-61%
(Study 3-4) and skiing 86-87% (Study 5-6) of maximal rate (Table
Autonomic nervous system
Morning heart rate in the supine position increased progressively
throughout the marching period being highest (p = 0.042)
on the day after the last march compared to the pre-exercise control
(Study 3). Heart rate in the standing position was first elevated
(p = 0.045) on the morning of the second day, and a highly
significant rise (p = 0. 006) was seen before the fourth
march compared to the pre-march control. The difference between
the standing and supine heart rates increased before the last march
and the day after, respectively, compared to the pre-march control
(p = 0.001 and 0.003).
There were no significant differences in the supine and standing
heart rates or in the difference between them before the first (Pre
I) and second (Pre II) skiing days (Study 5).
Summary of the musculoskeletal responses to daily repeated prolonged
exercise is presented in Table
The total pain index already increased by the first day of marching,
and reached its highest values on the third and fourth day (Study
1, 3). After the first march, pain was mainly (50-66%) focused on
the musculature of the calves, thighs and buttocks. The intensity
of the muscle pain varied from one to three (out of six) ("dull
ache" - "more slight pain"). During the last three
days, the pain was almost completely (60 to 91%) localised to the
feet. The pain intensity of abrasions and blisters of the feet varied
from two to six ("slight pain" - "very painful").
Joint symptoms in the lower extremities varied from 25 to 43% of
the subjects after the marches (Study 3). Almost all subjects (83-100%)
reported pain on the scoring scale "more slight pain"
on days III and IV, which was due to abrasions and friction blisters
of the feet (Study 1). "Other" pain was mostly caused
by abrasions from the straps of the backpack on the shoulders and
the intensity was one ("dull ache") (Study 1, 3).
Before the event skiers experienced no pain. After the first event,
however, pain increased (p = 0.04) and remained at a similar
elevated level (p = 0.013) after the second day. After skiing,
pain was focused mainly in the neck, shoulders, back and buttocks
and the intensity varied from one to three ("dull ache"
- "more slight pain"). One week later the perceived pain
had disappeared (Study 5).
Functional capacity of lower extremities
ROM measurements showed no impairment in the flexibility of the
hip flexors, knee extensors or flexors of either leg. The exercise
periods did not affect the results gained from maximal voluntary
vertical jumps. The circumferences of the calves and thighs remained
also unchanged in all studies (Study 1, 3, 5).
On the first and last day of the march serum total protein concentration
increased by 4% (p = 0.02) after the first march compared
with the pre-exercise level (Pre I) and by 3% (p = 0.04)
compared with the baseline (0) measurement (Study 4). After the
final march there was also a 4% increase in serum protein (p
= 0.007) compared with the pre-session (Pre IV) level.
A highly significant repeated exercise response was seen in serum
CK activity (p < 0.001) in all studies (1, 5). After the first
day's march, CK was increased when compared to the one-week or day
before measured baseline (p = 0.022 and 0.038, respectively), and
remained elevated (mean increase from 400 to 650%, p = 0.003-0.043)
until the end of the marching period. On the recovery day CK activity
returned to control levels. After the first day's skiing race, CK
was 62% higher than the pre-race level (203.8 vs. 125. 8 U·l-1,
p = 0.001). After the second day's skiing race, CK had increased
to 196% above pre-race level (371.9 vs. 125.8 U·l-1, p < 0.001)
and 42% above the level before the second race (371.9 vs. 262.1
U·l-1, p = 0.003). One week later, CK activity had declined significantly
(p = 0.014) below the post-race activity.
Table 13 contains a summary
of the endocrinological responses to daily repeated prolonged exercise.
In ANOVA a significant repeated march response was not seen in the
urinary excretion of catecholamines (Study 1). The acute response
to a single march was seen on the third day when excretion of noradrenaline
during the march was significantly increased by 233% (p = 0.027)
when compared to the exertion during the first march. Further, compared
to the preceding night it was 300% (p = 0.025). Also the excretion
of noradrenaline in the night tended to increase during the experiment
being 2.1-fold (p = 0.08) during the last night compared to the
night prior to the first march. On the fourth marching day there
was no more increase when compared to the excretion of the first
day (p = 0.17).
During the night preceding the first march the urinary excretion
of free adrenaline was below the method's detection limit. It increased
to 3.2 nmol·ml-1·h-1 (p = 0.018) during the night prior to the last
march. During the first three days the excretion of adrenaline during
the march was significantly (p = 0.02, 0.40 and 0.001, respectively)
greater than the previous rest excretion. In the case of adrenaline
the largest individual increase in the daily excretion during the
march was 10-fold, occurring during the third 24-h period of the
experiment. The difference between the previous rest excretion and
march excretion was not significant (p = 0.09) after the third day.
In the evening one week and one day prior to, as well as during
the first morning of the exercises (Study 1, 2, 4, 6), all hormone
concentrations were within the normal range for adult men, except
for the LH value in one subject (Study 6).
In the case of cortisol, the early morning value in study 1 was
significantly higher (p = 0.019) than the afternoon control value.
After the second march, cortisol was significantly lower (p = 0.020)
than the early morning value. As in the case of testosterone, ANOVA
showed no statistically significant differences between the afternoon
samples in study 1, but in study 4 a highly significant repeated
marching response was seen in the morning and afternoon (ANOVA,
p = 0. 01 and 0.0011, respectively). The acute response to a single
march on serum cortisol was only seen during the first day when
there was a 60% increase (296 vs. 474 nmol·l-1, p = 0.003) after
the first march. After that a downward trend was seen in the afternoon
samples (mean decrease from 8 to 19%, p = 0.09, 0.34 and 0.22, respectively)
compared with the previous Post sample.
During skiing (Study 6) there was a significant response to repeated
exercise in serum cortisol levels (p < 0.001). An acute response
was seen after both events when cortisol increased by 2.2- and 2.6-
fold, during the first and second days respectively (p < 0.001).
One week later (Rec) the C-level had returned (p = 0.028) to the
Pre I level.
In study 1, during the first morning, the serum testosterone level
was significantly higher (p = 0.030) than in the afternoon one-week
prior the march. After the first, second and fourth day of marching
testosterone significantly decreased (p = 0.029, 0.049 and 0.010,
respective) to less than 80% of the starting value. However, using
ANOVA, no statistically significant differences existed between
the afternoon samples (p = 0.5) in study 1. In study 4 a highly
significant repeated marching response was seen in the morning (ANOVA,
p = 0.001), but not in the afternoon (ANOVA, p = 0.21).
In testosterone serum levels a significant difference was seen in
study III after the second day of walking when testosterone was
reduced by 18% (p = 0.006) compared with the morning level for the
same day. After the first march, testosterone levels tended to decrease
by 15% (p = 0.06) from the preceding morning concentration. However,
pre- and post-march testosterone levels did not differ significantly
on the third and fourth day of the walk (p = 0.86 and 0. 50, respectively)
in study 3, and a plateau was reached by the third day.
A significant decrease due to repeated skiing in testosterone was
seen during the two- day's skiing (p = 0.001). An acute drop in
concentration in response to each exercise session was seen: testosterone
level was reduced by over 20% (p = 0.016 and 0.002, for the first
and second days respectively) compared with pre-race levels. One
week later (Rec) the testosterone level was restored (p = 0.031)
back to the Pre I level.
There was no significant response to repeated marching on serum
LH in study 2. Serum LH in study 4 revealed a highly significant
repeated march response in the afternoon (ANOVA, p = 0.0002), but
not in the morning samples (ANOVA, p = 0.12). The acute response
to a single march on LH was seen after each of the first three days
of walking. After the first march there was a slight upward trend
(3.9 vs. 5.0 IU·l-1, p = 0.07) and after the second and third march
LH was reduced by 31% (p = 0.04 and 0.001, respectively) compared
to the level after the first march. After the third march LH was
reduced by 37% compared with the pre-march sample (p = 0.001). However,
after the fourth march the acute response was no longer observed
(p = 0.11).
In serum LH there was a significant (p =0.020) response to repeated
skiing (Study 6). LH decreased after the first race by 37% and after
the second race by 44% (p = 0.028, both).
There was no significant response to repeated marching on serum
FSH concentrations in study 2, but in study 4, a highly significant
repeated march response on both morning and afternoon samples (ANOVA,
p = 0.01 and 0.0002, respectively) was found. After the first
march there was no acute response (p = 0.43). The acute response
to a single march in FSH was seen after the last three days of walking.
After the second, third and fourth march FSH was significantly lower
compared to the concentration the day before the march (0) (p
= 0.02, 0.02 and 0.03, respectively). Concentration of serum FSH
was reduced by 19% (p = 0.02) in the morning sample before
the fourth march when compared to the morning before the first march.
During skiing (Study 6) there was no significant response to repeated
exercise on serum FSH concentrations. After the second race there
was a decreasing trend in FSH by 13% (p = 0.064, ns.).
Mood states after daily repeated prolonged exercise
The total mood disturbance score was unchanged during all exercise
periods (Study 2, 3, 6).
The responses to repeated exercise (Table
14) were found in Fatigue-Inertia affective state (study 3 p
= 0.02, study 5 p = 0.01). In study 2 the Fatigue-Inertia
affective state was the highest after the first and in study 3 after
the last march. In the study 5 the Fatigue-Inertia affective state
was the highest after the second day of skiing.
15, and 10, male subjects were followed in this study during daily
repeated prolonged exercises under true field conditions. The subjects
were healthy and they marched 163 to 185 km over four days, corresponding
to a total of 200,000-250,000 steps (Sekiya et al., 1996)
or skied 100 km over two days. The purpose was to describe the responses
of cardiorespiratory, autonomic nervous, musculoskeletal and hormonal
systems, and mood states after daily repeated acute but non-competitive
prolonged walking and skiing during four days' of marching or two
days' of skiing events. The focuswas on the quantification of the
amount of possible disadvantage caused by physical activity. The
hypothesis of this study was that strenuous prolonged exercise during
consecutive days would decrease the functional capacity of the lower
extremities, disturb the balance of the autonomic nervous system
and the secretion of hormones from adrenal cortex and pituitary-testicular
axis. Further, negative changes in mood states were expected to
occur in concert with physiological responses.
Study design - strengths and limitations
The strength of this study is in its uniqueness: no similar multi-disciplinary
field study of daily repeated prolonged exercise has been published.
Vuori et al. (1979)
followed skiers daily, but collected data only after the first and
fourth days of skiing, not after the second and third. In the study
by Shephard (1991)
the daily skiing speed was very low, only 3.5 km·h-1,
and data were not collected daily. Furthermore, only hormonal responses
were followed in these studies.
Applied research, carried out in so-called real-world settings,
such as this, tends to address immediate problems, which limits
the control over research settings but yields results that are of
direct value to practitioners (Thomas and Nelson, 1990,
A field trial is not without limitations. The preliminary marching
study (1-2I) before conducting the primary marching data (Study
3-4) was carried out to reduce the methodological problems (Thomas
and Nelson, 1990,
p. 155). Studies 5 and 6 initially included only ten skiers out
of 5,692 Finlandia Ski Race participants, and one of these withdrew
due to a fall. These results were therefore obtained from a small
sample and may not be representative of the population of skiers
who participate in long-distance events.
The purpose of this kind of design is to fit the design to settings
that are more real world-like while controlling as many of the threats
to internal validity as possible. The purpose in reversal design
with time series is to determine a baseline measure, evaluate the
treatment (e.g. exercise), its return to baseline, evaluate the
new treatment, its return to the new baseline, and so on (Thomas
and Nelson, 1990,
p. 297-319) as follows:
O1 O2 T1 O3 O4
T2 O5 O6 (Thomas and Nelson, 1990,
p. 313), where O signifies observation or test (subscripts refer
to the order of testing) and T (treatment) signifies applied exercise.
A repeated measures design of this type has many advantages (Cook
and Campbell, 1979;
Thomas and Nelson, 1990,
p. 154-155). First, they provide the experimenter with an opportunity
to control for individual differences among subjects, probably the
largest source of variation in most studies. Secondly, inter-individual
variation differences can be identified and separated from the error
term, thereby reducing it and increasing the power of the analysis.
Thirdly, they are more economical in that fewer subjects are required,
and finally, they allow a phenomenon to be studied across time,
which is of particular importance in studies of change. However,
a repeated measures design is not without problems (Cook and Campbell,
1979; Thomas and
p. 155-156). Carryover (treatments given earlier influence those
given later), and practical effects (the dependent variables get
better as a result of repeated trials in addition to the treatment;
also called the testing effect), fatigue (subject's performance
is adversely influenced by fatigue or boredom), and sensitisation
(subject's awareness of treatment is heightened because of repeated
In experimental and quasi-experimental studies internal validity
means controlling all variables so that rival hypothesis as explanations
for the observed outcomes can be eliminated. External validity means
a generalisation of the results (Cambell and Stanley, 1963;
Cook and Campbell, 1979;
Thomas and Nelson, 1990,
There are eight variables, which are relevant to internal validity
and which might produce effects that confound with the effect of
the experimental stimulus if not controlled in the experimental
design (Cambell and Stanley, 1963):
1) history, the specific events occurring between the first and
second measurement in addition to the experimental variable, 2)
maturation, processes within the respondents operating as a function
of the passage of time, 3) testing, the effects of taking a test
upon the scores of a second testing, 4) instrumentation, in which
changes in the calibration of a measuring instrument or changes
in the observers or scores used may produce changes in the obtained
measurements, 5) statistical regression, operating where groups
have been selected on the basis of their extreme scores, 6) biases
resulting in differential selection of respondents for the comparison
groups, 7) experimental mortality, or differential loss of respondents
and 8) selection-maturation interaction, etc., which in certain
multi-group quasi-experimental designs might be mistaken for the
effect of the experimental variable.
The factors jeopardising external validity are: 1) the reactive
or interaction effect of testing, in which a pre-test might increase
or decrease the respondent's sensitivity or responsiveness to the
experimental variable and thus make the results obtained for a pretested
population unrepresentative of the effects of the experimental variable
for the unpretested universe from which the experimental responders
were selected, 2) the interaction effects of selection biases and
the experimental variable, 3) reactive effects of experimental arrangements,
which would preclude a generalisation about the effect of the experimental
variable upon persons being exposed to it in nonexperimental settings,
4) multiple-treatment interference, which is likely to occur whenever
multiple treatments are applied to the same respondents, because
the effects of prior treatments are not usually erasable (Cambell
and Stanley, 1963; Cook and Campbell, 1979).
If the number of subjects is small, as it especially was during
in the preliminary study (1-2), only the analysis of variance (ANOVA)
for repeated measures test can be used (Thomas and Nelson, 1990, p. 155). Repeated measures
ANOVAs have been thought to require the assumption (termed compound
symmetry) that all variables within a group must have equal variances,
all correlations among variables must be equal, and covariance matrices
of all groups must be equal. These assumptions are seldom met in
repeated measures studies, and they have been shown to be unnecessarily
strict (Cook and Campbell, 1979; Thomas and Nelson, 1990,
In this study the lack of a control group meant that many other
factors (e.g., the test environment, substance use, nutritional
status, stress level, sleep deprivation, previous activity, age,
sex, diseases) apart from the exercise may have had a confounding
effect for example on the hormone results. In addition, the data
collection and handling procedure (specimen collection, data manipulation,
and analysis) may admit confounding factors such as posture, circadian
and rhythmical variation, specimen collection and storage, choices
of specimens, analytical and biological variation, descriptive statistics
and inference (Tremblay et al., 1995). Most of these factors were partly standardised
in this design. The fact that no rest trial was used in this study
makes it difficult to draw conclusions about the responses to exercise
because the circadian rhythm of the hormones, the small variation
(± 1 h) in taking the post-exercise blood sample, and the systematic
time pattern between the days, could have influenced the results.
Anyway, during prolonged physical stress the circadian rhythm of
testosterone has been found to extinguish below the minimum and
that of cortisol abolish above maximum level of the control experiment
(Opstad, 1994). Nevertheless, what was interesting about this
study was that it took place during a prolonged real situation that
could not have been reproduced in a laboratory.
It is easier to establish reliability of measurement in research
than validity (e.g., stability, alternate forms, and internal consistency)
(Thomas and Nelson 1990,
p. 352). The coefficient of stability was determined by the test-retest
method on separate days. The alternate- forms method of establishing
reliability involves the construction of two tests, which both supposedly
sample the same material. An internal consistency reliability coefficient
can be obtained by e.g., the same-day test-retest, the split-half
method, the Kuder-Richardson method of rational equivalence, and
the coefficient alpha technique (Thomas and Nelson, 1990, p. 353). For instance, the error of testing jumps,
when compared with film analysis has been reported to be in the
order of ± 2% (Komi and Bosco, 1978) and the reliability coefficients for the repeated
measures of flexibility of the lower extremities have been reported
to vary from 0.90 to 0.98 (Wang et al., 1993). Also the circumference
measurement has been evaluated to be a reproducible method which
has been validated (Perrin and Guex, 2000). However, it is not always
correlated with leg (including foot) volume measurement (e. g. water
displacement method) and it measures the perimeter at a single level
(Perrin and Guex, 2000). To diminish the errors, the same technicians performed
all the field measurements in this study. Serum hormone concentrations
were measured using the commercial radioimmunoassay kits. The gonadotrophins
were assayed by immunofluorometry, which is a sensitive method for
detecting very low concentrations of gonadotrophins (Jaakkola et
al., 1990; Huhtaniemi et al. , 1992).
Physiological responses to daily repeated prolonged exercise
Cardiorespiratory loading in studies 1-4 were at the same level
as had been measured during a brisk walking speed (4.8-6.4 km·h-1)
when the heart rate of middle-aged men on a level surface had been
estimated to be 40 to 60% of maximal aerobic power and 50 to 70%
of maximal heart rate (Vuori, 1982; Rodgers et al., 1995). Energy consumption during
the marches in the present study, estimated by average walking speed,
body mass of the subjects, and the weight of the boots, was ca.
1,220-1,360 kJ·h-1 (290-324 kcal·h-1) (McArdle
et al., 2000,
p. 170), which means a total energy cost of 9.7-11.6 MJ (2,320-2,754
kcal) during 8-8.5 hours of daily activity. Oxygen uptake was approximately
17-20 ml·kg-1·min-1 (4.8-5.7 METs) (Holewijn
et al., 1992) which was 27% of VO2max
and 23% of oxygen uptake reserve (VO2R = [(VO2exercise-
1 MET)· (VO2max - 1 MET)-1] (Howley, 2001). The mean heart rate level was ca. 60% of the maximal
heart rate. At this level energy is produced aerobically, especially
through the oxidation of fatty acids. The intensity of endurance-type
exercise has been defined to be light if the percentage of VO2R
is between 20 to 39, percentage of HRmax 50- 63, and
VO2max 27-44 ml·kg-1·min-1 (3.2-5.3
METs) (Howley, 2001). The physiological threshold
of 'comfort' represents 70% of the maximum heart rate (Morris and
Hardman, 1997). De Wild et al. (1997) studied 97 over 70-year-old
men, who completed the 1993 Nijmegen Four-Day long-distance March
(30 km·day-1 on four consecutive days). The mean velocity
was 5 km·h-1 and the mean relative exercise intensity
was 52% of VO2max and 70% of HRmax. VO2max
was the most important predictor of the variation in self-selected
The skiers maintained the same mean heart rate in both days but
the mean skiing velocity during the free technique race (second
day) was 12% faster (5.0 vs. 4.4 m·s-1) than during the
classical technique race (first day). The effect of skiing technique
(diagonal stride or skating) at similar heart rate on the skiing
velocity was consistent with previous studies (Karvonen et al.,
1989; Bilodeau et al., 1991), in which the skating technique
has been determined to be 11-14% faster than classical skiing. The
mean heart rates during skiing indicated quite a high level of overall
cardiovascular strain (86-87%). This observation is in agreement
with that of other long-distance exercises lasting under 5 hours.
The metabolic and cardiac loads caused by a 42 to 90 km ski-hike
have varied from 64 to 85% of VO2max (Vuori, 1972)
and during a 90-km skiing event the respective heart rate represented
72. 8 ± 7% VO2max (Oja et al., 1988). During a 55-km cross-country ski race, heart rate
was maintained at 77% of the maximum for a mean duration of 4.4
hours (Kennedy and Bell, 1996), while in cycle races of 105 km and 110 km (2 h
35 min and 2 h 45 min, respectively), the heart rate was reported
to be 79% and 82% of the maximum (Palmer et al., 1994). Luurila et al. (1994) reported
that the highest mean hourly heart rates during 75 to 90 km race
skiing were 150 beats·min-1 and the maximum heart rate
was 161 beats·min-1, which occurred in most skiers (who
were in healthy middle-aged men) during the first hour of the race.
During strenuous cycling (Tour de France) 70% of the heart rate
has been measured to be under the first ventilatory threshold, 23%
between thresholds, and only 7% above the second ventilatory threshold
(Lucia et al., 1999). The energy expenditure of the cyclists for a period
longer than seven days has been reported to be from a mean of 25.4
MJ·day-1 to peak values of 32.7 MJ·day-1 (Saris
et al., 1989a) and 62% of energy was derived from CHO, 15% from
protein, and 23% from fat.
In cross-country skiing, fatigue may be a result from energy depletion
(e.g., glycogen, blood glucose), inadequate oxygen delivery (e.g.,
total haemoglobin mass) or disturbances in homeostatic functions
(e.g., fluid balance) (Rusko, 2003a). The study of Oja et al. (1988) suggests a trend of decreasing heart rate over
time in long-distance skiing. It was contented to relate to the
depletion of glycogen stores and the consequent shift towards fat
utilization as the energy source (Oja et al., 1988). This phenomenon would lead to a slower pace, but
unfortunately such changes were not followed in this study. Nevertheless,
skiing 50 km requires 15 MJ of energy, 99% of which is produced
by the aerobic breakdown of fats and carbohydrates (Rusko, 2003b).
The share of carbohydrates is 50 to 60% on average, but it can vary.
During the first 10 km, carbohydrate breakdown may provide 70 to
80% of the energy needs, but during the final 10 km this figure
may be lower than 20 to 30%. During 50 km of skiing, muscle glycogen
stores decrease to 10 to 15% of the starting level (Rusko, 2003b). An average weight reduction
of 2% after both skiing sessions in this study indicated probably
both muscle glycogen depletion and slight dehydration, which was,
however, compensated for by the next morning. However, there was
no haemoconcentration after the second day of skiing and the haematocrit
remained unchanged (Study 5).
In endurance events, especially in mass starts, it is possible to
pace up with another participant, which can result e.g. in skiing
a 6% reduction in total mechanical power output with speeds of 5.5
m·s-1 and no head wind (Street, 1990). The heart rate responses to skiing have been found
to be significantly lower (5.6%) when drafting than when leading
(Bilodeau et al., 1994) and in mass-start road races in cycling the HR
responses have been found to be more a function of tactical bunch
riding than of terrain (Palmer et al., 1994). Although the effect of
drafting on the heart rate could not be determined in this study,
the opportunity to draft during skiing could have influenced the
heart rate results. However, a reduction in total mechanical power
output caused by drafting cannot induce increased heart rate levels.
On the contrary, it could only have resulted in decreased heart
rates. Although many mass sporting events like the Finlandia Ski
Race emphasise participation rather than performance, the levels
of cardiorespiratory strain observed were indeed high and therefore
presented an increased risk of serious complications for subjects
with overt or latent cardiovascular disease (Vuori et al., 1983). Luurila et al. (1994)
found significantly increased arrhythmias in middle-aged men during
exhaustive prolonged exercise as compared to those observed during
a similar period of time of normal daily life. In 2003, for example,
two participants (both middle-aged men) in the Finlandia Ski Race
died. In men aged 50 to 59 years the incidence and relative risk
of sudden death in cross country skiing has been estimated to be
one per 0.7 million sessions or per 31,000 skiers per year (Vuori
et al., 1983).
has exemplified eventual precipiting factors analysing the situation
some minutes after the start of a ski race. First, most of the participants
are older middle-aged men and there are a number of persons who
are not completely healthy. Second, the excitement, lack of sleep,
smoking or alcohol use before the event. Third, the combination
of cold weather, full speed and an unprovided warm-up. Fourth, stumbles,
collisions, the competitive spirit and dehydration. Surely, all
these elements were present during the Finlandia Ski Race, but the
starts have been limited nowadays to groups of 500 skiers at one
time so that the rush and jam are reduced. The skiers are staggered
into the start groups according to their previous year's results.
Thomas et al. (1995)
have studied the physiological and perceived exertion responses
to six modes of submaximal exercise. On the 14-RPE trial, oxygen
consumption and oxygen pulse were significantly higher during jogging
than during other exercise modes. Ratings of perceived exertion
were significantly higher during cycling than during jogging. These
results indicated that different exercise modes have different cardiorespiratory
Oja et al. (1988)
recorded heart rate during mass events of 132-km cycling, 35-km
rowing, 33-km running, and 90-km cross-country skiing over one year.
The mean event time of the subjects was 4 h 58 min for cycling,
4 h 20 min for rowing, 3 h 30 min for running, and 8 h 29 min for
skiing. The respective mean heart rates represented 79.3, 72.9,
85.7, and 72.8% VO2max. The proportion of event heart
rates above the level representing the 90% event-specific maximal
heart rate was 31.2% in cycling, 17.9% for rowing, 59.7% for running,
and 21.6% for skiing. A statistical comparison of the mean event
heart rates indicated that the heart rate was lower in rowing than
in jogging and cycling and also lower in skiing than in jogging.
Their results showed that the cardiorespiratory strain of middle-aged
nonathletic men during long-distance mass events of cycling, jogging,
and skiing is high and relatively comparable to that of well-conditioned
Autonomic nervous system
In this study the significant elevations were observed in the morning
heart rate test after four days marching but not after two days
skiing. Dressendorfer et al. (1991)
found no changes in heart rate at rest after seven days of increased
training. During a 20-day Great Hawaiian Footrace the averaged morning
heart rate decreased during the first eight days and then progressively
increased, with significant elevations on days 17 and 20 compared
to day eight (Dressendorfer et al. 1985).
At rest, the heart rate setting depends on complex neurohumoural
interactions (Dressendorfer et al., 1985).
Dressendorfer et al. (2000)
suggests that a valid marker of insufficient physiological recovery
during excessive training is the elevated morning heart rate that
is persistently more than 10% above the normal baseline, as occurred
in this study. During six days of a moderate prolonged exercise
period heart rates increased by about 10% in the night, compared
to the previous control condition (Roussel and Buguet, 1982).
It was apparently not related to changes in body temperature, haematocrite,
sleep patterns, cortical adrenal or thyroid functions. The most
likely explanation for the nocturnal tachycardia was related to
the increased sympathoadrenal activity (Roussel and Buguet, 1982).
During physical activity musculoskeletal problems arise from external
(equipment, shoes and surface) and internal (anthropometric facts
and individual situation) variables as well as movement characteristics
(frequency), which influence the load and may be connected to pain
and injury (Nigg et al., 1984).
Further, the intensity and the amount of exercise are important
factors affecting the loading.
In 1993 and 1994, 35,101 and 33,834 walkers started Four-Day March
in Nijmegen, and 2,747 and 2,858 (7.83 and 8.45%) did not finish
it. The overall dropout rate in 1993 for first time participants
was 15.4% (Program-Magazine De 4 Daagse, 1994).
In Finlandia Ski Race (1995) 3% of 3,850 participants did not finish
the first day's race. During the second day 6% did not finished
the race (Finlandiahiihto, 2004),
which is more than in Vuori's (1972)
study. None of the subjects in the present study perceived musculoskeletal
or other health problems serious enough to discontinue marching
or skiing, or to necessitate medical attention during or immediately
after the event, except one individual who fell during the second
day of skiing and dislocated a finger. According the organizer's
statistics (unpublished data) there were 68 contacts to the first
aid during 2002 Finlandia Ski Race representing 1.6% of the participants.
Abrasions (n=26) and muscle cramps (n=15) were the greatest reasons.
In studies 1 and 3, the level of perceived pain (VAS-scale) was
already significantly higher after the first marching day, and more
pronounced after the last two marches. A similar time profile was
also separately found for lower limb pains, which focused on musculature,
joints and feet. Unfortunately the pain data was collected only
on the first and seventh/ninth day after the exercise, and not for
example 48 h after the last exercise. It is known that delayed onset
muscle soreness is greatest 1 to 2 days after the exercise (e.g.,
Clarkson and Tremblay, 1988; Enoka, 1994, p. 277), and with this protocol of the physiological
measurements that information was insufficiently received.
In a six-day track race the majority of musculoskeletal injuries
presented on the second day (Bishop and Fallon, 1999). Joggers, whose daily running
session lasted two hours, had persistent leg muscle soreness after
the third day (Dressendorfer et al., 1991). The rest of the perceived
pain in studies 1 and 3 were mainly due to abrasions on the shoulders
caused by the straps of the backpacks. When these two studies (1
vs. 3) are compared, slightly more acute muscle pains were reported
in study 3. This could be explained by subjects' lower training
background (6.0 vs. 9.3 h·week-1) and higher body mass
(79.4 vs. 74.4 kg). The proportion of subjects suffering from leg
muscle pain remained approximately the same (50%) but the mean scoring
of pain increased (score ranges "slight pain - painful")
until the end of the last march. Unfortunately pain scoring and
location data were collected using only a structured questionnaire.
Therefore the pain cannot be exactly located to specific muscles
as only muscle groups were indicated. The majority (ca. 65%) of
muscle soreness was experienced in the anterior and posterior thigh
muscle groups (quadriceps femoris and hamstrings) with the rest
(ca. 35%) located in the calf and gluteus muscles.
Anti-inflammatory analgesic drugs (acetylsalicylic acid, ibuprofen,
ketoprofen, indomethacin, naproxen) were used by four subjects in
study 1 during all marching days and in addition by one subject
during the last day. The average daily number of tablets (Burana®
400 mg, Ketorin® 50 mg) consumed per subject was 2, 3,
3, and 4 during the effort. In study 3 no one used anti-inflammatory
analgesic drugs during the first day. During the second day there
were three subjects and during the last two days seven who used
the drugs. The average daily number of tablets (Aspirin®
500 mg, Burana® 400-600 mg, Ketorin® 50 mg,
Ibusal® 200-400 mg, Orudis® 100 mg) consumed
during the last three days was 2, 3, and 3 in study 2. Beer was
used by some of the subjects after finishing the daily marches (half
to one litre per subject). In study V the use of analgesic drugs
or beer was not recorded.
Blisters and abrasions on the feet were some of the major problems
usually encountered during walking. For example, during the Exercise
Fastball in France, where soldiers marched 204 km in six days, all
of the injuries were due to foot disorders, such as blisters (Myles
et al., 1979).
The factor limiting performance for many of the subjects who marched
on the hard road surface has been the condition of their feet (Myles
et al., 1979).
The pain located in the hip, knee and ankle area might be of such
types as tendonitis, periostitis, or hydropsis, which are very common
medical problems during marching (Hedman, 1988;
Feet pain originating from friction blisters and abrasions were
experienced by almost every subject in studies 1 and 3. The locations
of the abrasions were those areas, which were evidently most exposed
to pressure and strong friction. The most important factors for
producing abrasions were the constant repetitive pressure on the
sole of the foot during walking as well as the frictional forces
exerted between the skin, socks and shoe soles. These shearing forces
generate mechanical fatigue in epidermal cells, leading most probably
to the loss of cell-to-cell integrity hence the development of blisters.
Tobacco use, ethnicity, foot type (pes planus), a sickness in the
last 12 months and no previous active duty military service experience
are blister risk factors in cadet basic training (Knapik et al.,
1999) but e.g.,
abnormalities of the foot were not significant factors in the development
of injury during recruit training (Rudzki, 1997c).
The subjects in studies 1 and 3 wore similar boots (weight 1,400
g) and cushioned them individually. Hard surfaces (asphalt and stone
covered roads) provide soft, cushion-soled footwear the ability
to allow mobility of the foot and ankle, as well as to dampen the
thight, prominent impact forces. On hard ground a boot is inferior
to running shoes in preventing problems due to walking or running
In addition, the temperature inside black boots will rise to very
high levels while marching in sunshine and this effect, especially
when combined with limited perspiration, is probably an additional
factor responsible for abrasions, especially at high speeds (Hedman,
1988). For example,
has studied the treatment of foot abrasions during a 160-km march
(four days), and he conjectured that about 50% of the treated cases
(n=39) would probably have been forced to stop the march if they
had not had access to hydrocolloid treatment. Of the 527 soldiers,
150 (28%) consulted a doctor in the course of the Four-Day March
in Nijmegen in 1996 (Hysing and Fretland, 1997).
Discomfort in the hip and shoulder areas could be reduced by adding
more padding to the pack harness surrounding the areas of the iliac
crest and shoulders. The pelvis rotates in the frontal plane opposite
to the shoulder girdle during most of the stride cycle. When walking
at a speed of 6.5 km·h-1, each foot will be lifted about
30 cm, and accelerated to twice the average velocity of the body,
and then decelerated to zero velocity again (Holewijn, 1990;
Holewijn et al., 1992).
When this movement is impeded due to the 10.4-kg load supported
by the shoulder, the trapezius muscle has to generate a 17 N extra
absolute force level (above walking with no load) per shoulder in
order to overcome this (Holewijn, 1990).
Lightening and reconfiguring the load to move it closer to the body
and improving load distribution have been recommended in an attempt
to alleviate symptoms associated with carrying heavy loads (Johnson
and Knapik, 1995).
In contrast to a previous study of strenuous road marching (Knapik
et al., 1997),
low back problems were not a major issue in studies 1 and 3. The
reason for this difference may be the lightweight load carried and
the non-maximum walking speed. When biomechanical and metabolic
effects of varying backpack loading on simulated marching was studied
(Quesada et al., 2000)
notable declines were observed for knee extension moment peaks suggesting
that the knee may be effecting substantial compensations during
backpack loaded marching. On the contrary, kinetic data indicated
that such knee mechanics were not sustained, and suggested that
excessive knee extensor fatigue may occur during prolonged loaded
walking (Quesada et al., 2000).
An optimum method of load carrying should induce stability, bring
the center of gravity of the load as close as possible to that of
the body and rely on the use of large mass muscles (Legg, 1985).
The concept of distributing the load mass more evenly around the
center mass of the body has both positive and negative aspects (Knapik
et al., 1997).
Feet and shoulder problems could most probably be completely eradicated
by means of considerations and technical solutions. The musculoskeletal
loading during prolonged exercise could be adjusted by changing
the gait and carrying technique. For example, Bishop and Fallon
(1999) argued that
there might be another reason beside the onset of blisters for the
gait changes. This second possible factor is "favouring"
injuries, which are present already at the start of the race or
those that develop during the race, and lead to gait changes and
increased stresses elsewhere.
Military basic recruit training is known to be associated with an
increased risk of overuse injuries (e.g., Ross, 1993a;
1993b; Jordaan and Schwellnus, 1994).
The overall incidence of injuries in military recruits undergoing
basic training was 1.8/1000 training hours (Jordaan and Schwellnus,
1994), but a much
higher rate of injuries (13-15/1000 h) was found in Rudzki's (1997a)
study where field training was not included. Overall, most injuries
treated in US Army outpatient clinics were lower extremity training-related
injuries (Jones and Knapik, 1999). The highest incidence of injuries was recorded
in weeks one to three and week nine of training, which were weeks
characterised by marching (> 77% of the training time). The amount
of overuse injuries may be diminished, if the possible overpronation
is diagnosed with orthoses (Lehti and Rehunen, 1992), and training is modified
(Jordaan and Schwellnus, 1994). The lower marching volume did not lessen morbidity
(Giladi, et al., 1985).
In cross-country skiing the most common overuse injuries to the
upper extremities are tendonitis/tendinosis of the rotator cuff
and of the distal triceps or brachii of the proximal biceps, impingement
syndrome or subacromial bursitis, and epicondylitis (Ronsen, 2003).
In lower extremities the most common overuse injuries in cross-country
skiers are inflammation of the hip adductors, external rotators
or flexors, tibialis anterior, plantar fascia and Achilles' or flexor
hallucis tendon, minor tears or spasms in the hip or leg muscles,
iliotibial band friction syndrome, patellofemoral pain syndrome,
and medial tibial stress syndrome/shin splint (Ronsen, 2003).
The most common injuries to the trunk/spine are inflammation of
muscles, tendons, ligaments and joints, spondylolysis and spondylolisthesis,
lumbar disc degeneration, protrusion and herniation, and scoliosis
or Scheuermann's disease in the thoracic spine (Ronsen, 2003).
In cross-country skiing, fatigue may also be of neuromuscular origin
(decreased central recruitment and peripheral force production)
No significant changes in the functional capacity of the lower limbs
(vertical jumps, range of motion, circumferences) were observed
in the present study. The high volume of walking was assumed to
decrease the functional capacity of the lower extremities, because
for example, even a single marathon run has caused an acute loss
of muscle function (Sherman et al., 1984; Nicol et al., 1991a; 1991b;
Kyröläinen et al., 2000). Hence, the discrepancies between our results and
those seen after marathon running are evidently caused by the extremely
heavy and competitive nature of those events. Walking compared to
running causes 3.6-fold lower ground reaction forces (Voloshin,
similar to the present results, no significant changes in the leg
muscle fitness test results (e. g., vertical jump test) have been
found after 20-days of running (Dressendorfer and Wade, 1991). Limitations of the range
of motion of any lower extremity joints will disrupt gait mechanics
and have been found to be associated with an increased risk of ulceration
In the present study, a relatively moderate increase (400 to 825%)
was observed in serum CK throughout the marching periods. An increase
of this magnitude can well be caused by facilitated protein transfer
via the lymphatics from muscle interstitium, and not necessarily
from the myocellular compartment into intravasal compartments (Komulainen
et al., 1995).
Therefore, great care must be taken when interpreting such small
changes in serum CK as in this study (max. increase 9.2-fold) and
e.g. , in the study done by Ross et al. (1983;
seven fold increase), to mean serious pathophysiological phenomena
in a muscle, in contrast to, for instance, changes after eccentric
bench-stepping exercise, when CK increases may be 350-fold (Newham
et al., 1983).
In study 5, CK activity increased only about 3 times from the initial
value. This is in accordance with an earlier 90 km skiing study
(Refsum et al., 1972).
Urinary catecholamines were assayed in order to quantitatively estimate
sympathoadrenal stress. Both adrenaline and noradrenaline excretion
rates showed cumulative sympathoadrenal stress during marching period,
seen not only as cumulatively increasing excretion during the successive
marches, but also, interestingly, as a tendency for cumulatively
increasing night excretion. Due to a lack of reference data, the
evaluation of the usefulness, especially during night excretion,
of catecholamines as an estimate of general sympathoadrenal stress
remains open. A similar type of cumulative sympathoadrenal loading
response was found in the skiing study of Vuori et al. (1979)
where the basal noradrenaline plasma levels were increased during
the first days of a ski-hike. In four days, they reached a plateau.
The only acute increasing response of the adrenal cortex to marching
was measured after the first exercise session in study 3, despite
the peak value accruing in the morning (Marniemi et al., 1984). Either overall hormonal
stress adaptation occurs in about a day for the present type of
prolonged walking or fatigue induced by the prior exercise may have
modified the hormone response by provoking a feedback suppression
as demonstrated by Brandenberger et al. (1984).
The suppressed response reported here was more rapid than that seen
in earlier studies (for example, Marniemi et al., 1984; Fellmann et al., 1992) in which stabilisation occurred
over three days. During the last three days both pre- and post-concentrations
of serum cortisol levels gradually decreased towards normal resting
values. Serum cortisol was no longer elevated after the last walk
or on the following morning after, when compared with the baseline
samples taken before the first march. A significantly elevated cortisol
level was still detected after nine days of recovery, but this could
have been due to the circadian rhythm of cortisol secretion since
the recovery sample was taken earlier than the Post samples following
the marches (1:00 to 2:00 vs. 2:30 to 6:30 p.m.).
It is generally accepted that during prolonged severe exercise the
secretion of cortisol and therefore blood levels as well are progressively
increased (Marniemi et al., 1984). Lowered or suppressed cortisol responses to subsequent
exercise have been speculated to represent a maladaptation or pathology
in the athletes (Lehmann et al., 1998; Hackney and Styers, 1999).
Viru et al. (2001)
found two different types of resetting of the regulation of pituitary-adrenocortical
activity to subsequent exercise after prolonged (2 h) continuous
running: one involved an intensified mobilisation of pituitary-adrenocortical
function while the other reflected the inhibition of activity within
this system produced by the fatigue.
After the first and second days of walking, the concentration of
serum testosterone decreased when compared with the pre-march baseline,
but not after the third and fourth days. There was also a significant
decrease after the second day compared with the morning level. Hence,
secretion of testosterone appears to adapt to repeated prolonged
(8 to 11 h) low intensity (57 to 61%) walking within three days.
Although the concentrations of anabolic hormones (testosterone,
LH, FSH) before the event were within the reference limits i.e.,
they were quite low. Therefore it is presumable that changes in
initially lower hormone concentrations will be smaller than in higher
levels. Endurance trained men, such as the subjects of the present
studies, who had trained for six to nine hours per week, have been
reported to have a lower basal serum testosterone concentration
than control subjects (Wheeler et al., 1984; Hackney et al., 1990; Gulledge and Hackney, 1996).
LH tended to increase during the first day and significant decreases
were seen after the second and the third day when compared to the
pre- march baseline. The decrease was also seen after the third
day compared to the morning level, but there were no changes during
the fourth day. Hence, the acute response at the pituitary level
of the hypothalamic-pituitary-testicular axis (excluding secretion
of FSH) also seem to disappear within four days. No acute march
response on FSH was seen during the first day, but thereafter FSH
declined during the last three days and the pre-march concentration
of FSH did not rise significantly between the end of the third and
the beginning of the last exercise session. Thus, no adaptation
to repeated low intensity prolonged walking was seen in FSH. The
difference in these results compared with studies that have detected
no decrease in gonadotropins after prolonged exercise (Dessypris
et al., 1976; Schürmeyer et al. , 1984;
Lucia et al., 2001)
may partly be explained by the improved precision and accuracy of
the analytical method (IFMA) used in this study (Jaakkola et al.,
1990; Huhtaniemi et al. , 1992).
Earlier studies have reported a higher concentration of serum FSH
in trained subjects, which is considered to be a sign of compensating
hypogonadism due to several years of physical training or dysfunction
of the Sertoli cells (Vasankari et al., 1993). These conclusions are in accordance with the present
results. The secretion of FSH is unlikely to adapt to repeated prolonged
The results of the body mass and haematocrit in study 6 was similar
to marathon runners during a 20-day road race (Dressendorfer et
al., 1981). An
average body mass reduction after each walking session (1 to 2%)
indicated slight dehydration, which was, however, compensated for
by the next morning. However, possible haemoconcentration caused
by dehydration could not induce the reduction of postexercise serum
concentration of testosterone, LH or FSH. On the contrary, possible
haemoconcentration could result instead in increased concentrations.
Sleep deprivation or a low-energy diet, which could have a major
influence on the hormonal results, were not included in this study,
and all subjects were healthy adult men. The hormonal comparisons
were made with the baseline samples (PreI samples and 0 p.m. samples),
which make the interpretation of the change possible.
Mood states after daily repeated prolonged exercises
Although significant increases in mood disturbance within a period
of 3 to 4 days following the onset of increased loading may be provoked
(Morgan et al., 1988), no significant changes in mood states were found
in this study. After the daily marches the soldiers felt tired,
listless and sluggish but not totally exhausted or fatigued. The
mood factors (Fatigue-Inertia and Vigor-Activity), which contain
an obvious somatic component, are found to display the greatest
alterations (Raglin et al., 1991). The increase in the Fatigue-Inertia and the decrease
in the Vigor-Activity affective state during the 4- day march represented
a mood of weariness, inertia and low energy level. The increase
in the Tension-Anxiety affective state represented a heightened
musculoskeletal tension. It included the reports of somatic tension,
which may not be overtly observable (tense, on edge), as well as
observable psychomotor manifestations (shaky, restless). Overall,
the present results indicate that the participants could cope with
the psychological stress and repeated monotony of prolonged exercise
over 4 days without notable mood changes.
Also after two days of skiing the subjects felt tired, listless
and sluggish but not exhausted or fatigued. The increase in the
Fatigue- Inertia affective state represented a mood of weariness,
inertia and a low energy level.
Usually improvements in mental health are associated with aerobic
exercise, but the results of a study by Hale et al. (2002)
indicate that combined sessions of aerobic and resistance exercise
reduced anxiety, and that the order in which the exercise is preformed
does not influence this response. The same kinds of results have
been found in acute resistance training (Hale and Raglin, 2002).
Anxiety has been found to decrease following different intensities
(40-70% VO2peak). However, this reduction was delayed
somewhat following exercise at a high intensity (Raglin and Wilson,
1996). When O'Connor et al. (1991)
studied the effects of 3 days of increased training in swimmers;
significant reductions in vigor were observed as a consequence of
the greater training load.
Recommendations for future research
Exercise stress elicits varied responses in different subjects,
and frequently identical exercise stress will elicit varied responses
in the same person at different times. This is called individual
specificity of exercise (Edington and Edgerton, 1976,
p. 4). Therefore the results of field studies are situational and
the background of the subjects and exertions must be well described.
Different exercises have different biological requirements. Exercises
could be classified according to the speed of movement, resistance
to the movement, and duration or the time over which the movement
has to be repeated. These three classification components are simultaneous
and additional variables affecting the activity or environmental
factors must be taken into consideration. Mental and social pressures
and dietary considerations must be added to the total consideration
for exercise classifications (Edington and Edgerton, 1976,
In this study the types of exercises were walking and skiing, but
many other endurance exercise types could also be very prolonged,
for example cycling, golf, orienteering, paddling, rowing, running,
skating, and swimming, and provide fields of investigating. The
physiological responses of these long lasting aerobic exercises
should also be studied within the normal population (both men and
women, young vs. older people) and not only in regularly training
and competing athletes because the responses could be different.
It would be important to find the limit beyond which signs of over-dosage
may develop. This may be the reason why many discontinue their training
programs, which they have started with great hopes. The critical
borderline to physiological overload during daily repeated exercise
still remains open and further investigations are needed.
The present findings can be generalised partly to the army and other
physically strenuous occupations. In the soldier's action competence
model (Toiskallio, 1998) four elements can be distinguished, i. e. 1) physical
fitness/performance, 2) psychological, 3) social, and 4) ethical
competence. A soldier in action forms part of the situation and
the environment where he acts. The soldier's action is contextual.
Mental strength is an important ability, and can be seen as stamina,
determination, bravery and the will to win (Defence Staff, Finnish
Defence Forces, Department of Education 1999).
From the holistic perspective, the same elements could also be seen
in sports. When functional capacity and working ability or the athlete's
training state are under evaluation or research in the field environment,
components other than physical fitness/performance are worth remembering
main findings and conclusions of the present series of studies
on fit male volunteers can be summarised as follows:
The cardiorespiratory response to daily repeated walking over
8 hours was moderate (60% of maximum heart rate) and to daily
repeated 3 hours skiing it was strenuous (90%).
The increased orthostatic heart rates were found after four
days of very long, and moderate walk, but not after the shorter
but more strenuous ski race.
Muscle pain was perceived during and after the two different
exercise series, but neither very long, moderate walking nor
long, strenuous skiing induced any changes in the functional
capacity of the lower extremities.
Catecholamine excretion rates during marching indicated cumulatively
increased sympathoadrenal stress. A daily repeated prolonged,
moderate walk and a strenuous, long lasting ski event evoked
the hormonal secretion of the adrenal cortex (cortisol) and
pituitary-gonadal axis (testosterone, LH, FSH), but the response
disappeared within four days of repeated prolonged exercise
(excluding the secretion of FSH after maching) and no dramatic
long lasting changes occurred.
Fatigue was perceived after the two different exercise series,
but total mood state was stable.
Incorporation of multidisciplinary research allows for the
collection of holistic information during field studies where
physical as well as psychosocial competencies are present.
study was carried out in LIKES Research Center for Sport and
Health Sciences in Jyväskylä, Finland, during the years of 1993-2003.
There are several persons who have contributed to my work and
whom I want to express my gratitude:
First, I would like to acknowledge my supervisors: Docent Veikko
Vihko, PhD, LIKES-Research Center, Jyväskylä, Professor Osmo
Hänninen, MD, PhD, Department of Physiology University of Kuopio,
and Docent Matti Mäntysaari MD, Research Institute of Military
Secondly, I thank my co-authors: Docent Pirkko Huttunen, MD,
PhD, Department of Forensic Medicine, University of Oulu, Docent
Tommi Vasankari, MD, Paavo Nurmi Center and Department of Physiology,
University of Turku and Finnish Sports Institute, Vierumäki,
and Docent Jyrki Komulainen, PhD, LIKES-Research Center, Jyväskylä.
I am grateful to Emeritus professor Ilkka Vuori, MD, PhD, and
Professor Urho Kujala, MD, the rewievers of this thesis, for
their valuable suggestions and criticism, and to Ms. Irene Koutsoukis,
BScH, for the revision of the English language.
In addition, I would also like to thank Dr. Jan A. Vos, MD,
University of Nijmegen, The Netherlands, Ms. Anneke Geurts,
Radboud Hospital, Nijmegen, The Netherlands, Dr. Henri Tuomilehto,
Dr. Heikki Mustonen, the Finnish Military Sports Federation,
National Defence College; First Degree Division (Military Academy),
the Central Support Command Military Personnel of The Netherlands,
and the Finlandia Ski Race Organizing Committee for their valuable
help in organizing this study. I am also grateful to Ms. Ulla
Hakanen, Mr. Eino Havas, MSc, Ms. Pirjo Tolvanen, and Ms. Leila
Vilkki in the LIKES-Research Center for their assistance and
help during this study.
My warm thanks belong to the members of "thirtysomething".
Finally, I thank my wife Sirpa and my son Ville, and I dedicate
this book to the loving memory of my other son, Aleksi. The
greatest question of the world is the mystery of the life!
This study was financially supported by the LIKES-Foundation
for Sport and Health Sciences, the Scientific Consultation Board
of the Defence Forces (MATINE), the Research Institute of Military
Medicine, the Foundation of Pajulahti Sport Institute, Lahti
Polytechnic, and the Finnish Genealogical Väänänen-Family. The
original papers are reproduced by the permission from the Association
of Military Surgeons of U.S. (Bethesda, USA), Association of
Military Medicine in Finland (Helsinki, Finland), Springer-Verlag
GmbH & Co. KG (Heidelberg, Germany) and Minerva Medica (Torino,
Research interests: Exercise physiology