REDUCED
MUSCLE PAIN INTENSITY RATING DURING REPEATED CYCLING TRIALS
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School of Human Movement Studies, Charles Sturt
University, Bathurst, Australia
| Received |
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16 January 2004 |
| Accepted |
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20
February 2004 |
| Published |
|
01
June 2004 |
©
Journal of Sports Science and Medicine (2004) 3, 70-75
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| ABSTRACT |
| The
purpose of this study was to investigate muscle pain intensity rating
using a 10-point category-ratio pain intensity scale during self-paced
cycling exercise within three trials. Eleven subjects (age 21.4 ±
2.6 years; VO2 peak 3.3 ± 0.9 L·min-1)
performed a 60-min cycling trial on three occasions. During each trial
subjects cycled at the utmost work intensity for 60-min. To simulate
competitive training, 1-min maximal effort sprints were performed
every 10-mins into the trial. Ambient temperature and relative humidity
were set at 33 ± 0.7 oC and 63 ± 2.0%, respectively.
During exercise, subjects ranked the muscle pain intensity at 5 min
intervals and following each sprint effort. Simple main effects revealed
that muscle pain intensity ratings were significantly lower in trial
3 compared with trial 1 at the 50 min [F = 4.5(2 30); p = 0.015, eta2
= 0.05], 55 min [F = 4.89(2, 30); p = 0.011; eta2 = 0.05], and 60
min [F = 3.6(2, 30); p = 0.034; eta2 = 0.04] time interval. Repeated
measures ANOVA revealed a significant increase in the mean distance
cycled amongst the trials (p < 0001). These results indicate an
attenuation in muscle pain intensity rating with endurance exercise
training when performed over three trials. The reduced pain intensity
rating may be due to adjustments in cadence and gear selection amongst
the trials.
KEY
WORDS: Pain, intensity, training, rating, cycling.
|
| INTRODUCTION |
|
The
experience of pain and discomfort during intense exercise is well
recognised however there is a surprising deficit of research in
this area. Investigations into pain during physical exertion were
first published in the 1960's when Caldwell and Smith (1966)
reported on pain intensity during an isometric endurance task. In
a study by Lloyd (1972)
subjects rated the pain during an isometric muscle contraction from
just 'noticeable pain' to 'intolerable pain' between 10 and 50 seconds
into contraction. In a recent study by Cook et al. (1997)
pain was assessed during a ramped cycle ergometry test to exhaustion.
The study found that the rating of leg muscle pain increased as
a positively accelerating function of relative exercise intensity.
Furthermore, the total pain index reported by subjects following
the exercise test elicited greater sensory and affective variables
compared to pain stimuli typically used in experimental settings
(Cook et al., 1997).
Several methods have been applied to quantify the individual sensation
of pain. Tools such as the category ratio scale can be applied to
assess pain intensity during the performance of dynamic exercise
(O'Connor and Cook, 1999).
The administration of category ratio (CR) scales in measuring pain
has been shown to be valid and reliable. In research by Cook et
al. (1997), a
CR scale was developed by combining the verbal anchors from the
Pain Perception Profile (Tursky et al., 1982)
with features of the easily administered 0 - 10 CR Borg scale (Borg,
1990). The 0
- 10 CR Pain Intensity scale was found to be a valid and reliable
tool in assessing pain intensity and peak pain values during physical
exercise (Cook et al., 1997).
The number of investigations in pain response with exercise training
are limited. In a study by Scott and Gisbers (1981),
tolerance to ischaemic pain in competitive swimmers was found to
differ with the training status of the athletes. The study noted
that changes in pain tolerance during the training season indicated
a short-term adaptation to pain as a result of systematic exposure
to brief periods of intense exercise. In a study by Egan (1987),
it was suggested that training for specific sports may desensitise
athletes to pain.
Few studies have reported on the rating of muscle pain intensity
during vigorous and enduring physical exercise and there is an absence
of research determining muscle pain intensity rating during self-paced
exercise training trials. Therefore the purpose of this study was
to assess muscle pain intensity rating during the performance of
self-paced cycling exercise amongst three repeated trials.
|
| METHODS |
Subjects
Eleven cyclists (eight men, three women) with a range of cycling abilities
were recruited for the study. All participants were apparently healthy,
having completed a health history questionnaire. The participants
were physically active individuals and were familiar with cycling
exercise and the performance of intense physical activity for extended
periods. The study was conducted with the approval of the Charles
Sturt University Ethics in Human Research Committee and all subjects
signed a letter of informed consent.
Descriptive measurements and peak oxygen uptake (VO2 peak)
were obtained during a familiarisation session before participating
in three repeated cycling trials. For determining body fat, skinfold
measurements were collected from triceps and subscapular in duplicate
using skinfold callipers (British Indicators Ltd, England). The percent
bodyfat was determined using the method described by McArdle et al
(1991). Standing
height was measured to the nearest 0.1 centimetre using a precision
stadiometer (Len Blaydon, Lugarno, Australia) while body mass was
measured to the nearest 10g using an electronic precision balance
(HW-100KAI, GEC, Avery Ltd, Australia). The participants diets were
not monitored or restricted however they were requested to abstain
from the consumption of alcohol, caffeine and tobacco for 24 hours
prior to each trial. Subjects were requested to perform the same type
of physical activity for the duration of the study and to refrain
from heavy physical exercise on the day prior to the time trial.
The VO2 peak was determined by an incremental test with
the subjects own bicycle mounted to an electromagnetic trainer (Tacx,
Technische Industrie Tacx BV, Wassenaar, Netherlands). Subjects performed
the test in mild temperature conditions (22-24 oC; humidity
40-50%). During the test subjects breathed through a two-way non-re-breathing
valve (series 2700 large, Hans Rudolph, St Louis, MO, USA). Expired
air was sampled by an automated gas analyser (Quinton Instrument Company,
Bothel, WA, USA). Before each test the pneumotach (Hans Rudolph, St
Louis, MO, USA) and gas analysers were calibrated using a 3 L syringe
and gases of known concentration, respectively. Expired air passed
through a mixing chamber of 5.5 L volume and was sampled at 30 s intervals.
Following a brief low intensity warm up, the incremental test commenced
at a workload of 100 W and increased by 10 W at 30 s intervals until
the subject could not maintain the required workload. Subjects were
required to remain in a seated position during the test. The highest
VO2 that could be maintained for one minute was deemed
to be the VO2 peak.
Exercise
training protocol
Subjects were required to complete three cycling time trials in
warm humid conditions. The aim was to cycle the greatest distance
possible within the allotted 60 minutes, adjusting pedalling speed
and gear ratio as required. A higher temperature and humidity were
established to simulate intense training conditions during cycling
in a warmer climate and to determine the exercise protocol reliability,
as previously published (Marino et al., 2002).
The temperature and humidity was set at 33 ± 0.7oC
and 63 ± 2.0%, respectively. Trials were separated by at
least 5 days to avoid partial heat acclimation through the trials,
and within 14 days. A fan providing a constant wind speed of 2 ms-1
was positioned directly in front of the subject. Subjects were allowed
to drink water ad libitum throughout each trial.
The trial was performed by subjects using their own bicycle mounted
to an electromagnetic cycle trainer. The cumulative distance cycled
and the power output was recorded at 5 minute intervals. The distance
travelled and power output was recorded from the digital display
unit connected to the cycle trainer. The cycle trainer was calibrated
for distance accuracy before each trial by recording the pedal revolutions
required to cycle 5 km. This procedure yielded a coefficient of
variation of 0.7%. During each trial, subjects were permitted to
alter gear ratio and cadence as required. This procedure provided
a self-selected exercise intensity, as is often performed during
exercise training.
In order to provide an additional measure of performance and to
simulate intense training conditions, subjects were also required
to perform 60 seconds of maximal effort 'sprint' exertions every
10 minutes into the trial. During the non-sprint phases, subjects
could return to a self-selected cycling intensity. Subjects were
provided with on-going performance results including elapsed time,
heart rate, and a time count leading into each sprint effort.
Pain
Intensity data collection
During each cycling trial, a category ratio pain intensity scale
with verbal anchors was displayed in front of the subject for viewing
during exercise. The scale was numbered 0 - 10. The verbal anchors
and numerical vales for the scale are as follows; 0 no pain at all,
½ very faint pain, 1 weak pain, 2 mild pain, 3 moderate pain, 4
somewhat strong pain, 5 strong pain, 7 very strong pain, 10 extremely
intense pain (almost unbearable). Subjects were instructed to view
the scale and apply it to rank the intensity of pain in the thigh
muscles at each moment of report during cycling exercise. The verbal
ranking of the pain intensity was acquired every 5 minutes into
the trial. The pain rating for the sprint phases were obtained immediately
after each sprint effort. The ratings at 10, 20, 30, 40, 50, 60
min represent the pain intensity during the sprint phases of the
trial. The ratings at 5, 15, 25, 35, 45, 55 min represent pain intensity
for the non-sprint phases during self-paced exercise.
Statistics
The data for pain intensity were analysed by a 2-way repeated measures
ANOVA (TIME x TRIAL). Significant interactions were analysed by
simple main effects and Tukey's HSD post-hoc procedure was used
where appropriate. When appropriate, the eta2 was used
as a measure of the magnitude of association among variables. Rough
estimates for the strength of association for a given eta2
value are that 0.01 is considered a small effect, 0.09 medium, and
0.15 large. The data for cycling distance were analysed by 1-way
repeated measures ANOVA for trial. The data for power output were
measured by 2-way ANOVA (TIME x TRIAL). All data are presented as
mean ± SD and the level of significance was set at p < 0.05.
|
| RESULTS |
Descriptive
characteristics of subjects
The mean age of the subjects was 21.4 ± 2.6 years, height 176.3
± 10.8 cm, weight 74.9 ± 10.0 kg, body fat % 14.2 ±
5.0, VO2 peak 3.3 0.9 L·min-1, peak power output
322.8 ± 86.3 watts.
Muscle
Pain Intensity ratings during three cycling trials
The muscle pain intensity ratings during the three cycling trials
are presented in figure 1.
There was a significant main effect for exercise time [F = 118(2,
30); p < 0.001; eta2 = 0.54], indicating a significant
increase in muscle pain intensity rating during exercise. There
was a significant exercise time by trial interaction [F = 6.3(2,
30); p = 0.005; eta2 < 0.01]. Post hoc comparisons
revealed that muscle pain intensity ratings were significantly lower
in the third trial compared with trial 1 at the 50 min [F = 4.5(2,
30); p = 0.015, eta2 = 0.05], 55 min [F = 4.89(2, 30);
p = 0.011; eta2 = 0.05], and 60 min [F = 3.6(2, 30);
p = 0.034; eta2 = 0.04] time interval.
Cycling
performance in three cycling trials
Repeated measures ANOVA revealed a significant increase in the mean
distance cycled amongst the trials (F = 14.163(2, 32); p < 0001;
eta2 = 0.01). The mean distance cycled for trials 1, 2 and 3 were
26.3 ± 5.0, 27.7 ± 5.7 and 28.1 ± 5.6 km, respectively. The distance cycled
in trial 1 was significantly different from trial 2 (p < 0.01)
and 3 (p < 0.001). The mean power output for trial 1, 2 and 3
were 229 ± 48, 241 ± 74, 224 ± 53 W, respectively. There was no main effect
for power output by exercise time (F = 1.9; p = 0.176) or exercise
time by trial interaction (F = 1.9(2, 30); p = 0.161).
|
| DISCUSSION |
The
main finding in the present study was that muscle pain intensity rating
decreased over the three endurance cycling trials during exercise.
The rating of muscle pain intensity was significantly attenuated in
the final stages of the third trial. Vecchiet and Galletti (1979)
reveal that a reduction in the intensity of the sensation or an increase
in the latency to onset or, an increase in the level of the workload
at which pain appears for the first time are apparent with training.
Several studies on pain have assessed pain ratings in the acute post-exercise
phase by assessing pressure pain threshold (Koltyn et al., 1996;
Perrsson et al., 2000).
Previous research reveals that pressure pain responses are also effected
by exercise training (Scott and Gijbers, 1981).
In a study by Waling et al. (2000),
pressure pain responses were significantly reduced in groups that
performed strength and endurance training over ten weeks. However,
the present results indicate that there is a reduction in the rating
of muscle pain during cycling exercise with repeated trials. This
is in contrast to research by O'Brien and O'Connor (2000),
showing a consistent muscle pain intensity rating with repeated trials.
The contrast in results may be associated with differences in the
exercise duration. The exercise duration in the present study was
40 min longer than the study by O'Brien and O'Connor (2000),
and significant differences in pain rating in the present study were
revealed in the later stages of the third trial.
Muscle pain rating during exercise has been shown to positively accelerate
with the relative leg power output and oxygen consumption during ramped
cycle ergometry (Cook et al., 1997).
This suggests that the rating of muscle pain intensity is associated
with exercise work intensity. However, the present results reveal
a diminution in muscle pain rating between trials with no significant
difference in leg power output. Although the power output remained
consistent, there was a significant increase in cycling distance covered
between trials. It would be expected that an increase in distance
performance would also result in an increase in power output. The
disparity in results may be associated with the measurement procedure.
The present study applied a flexible work intensity protocol which
permits the subject to modify gear ratio, cadence and power output
during exercise, as is often performed during training. This allowed
for dynamic variations in power output within each exercise trial.
Moreover, the measurement of power output was recorded at the moment
of report and the distance covered was a continuous cumulative measure
over the time trial. The disparity between power output and cycling
distance could be minimised with more frequent recording of power
output during exercise. Other limitations within the present study
may have also effected the results to some extent. The small sample
of subjects, absence of monitoring the intake of substances such as
caffeine (Motl et al., 2003)
or medications, and the limited supervision of the subjects training
schedule apart from the trials, could have effected the outcome. Subjects
were briefly informed to maintain their regular training schedule
and to abstain from caffeine and heavy exercise 24 h prior to each
trial. However, the present data indicate that with endurance cycling
trials there is a reduction in muscle pain intensity rating despite
a significant increase in the cycling distance performance.
It is possible that the reduced pain rating in the present study may
be associated with a training induced hypoalgesia. However, previous
research indicates that alterations in cycling cadence (pedalling
frequency) can significantly effect muscle pain intensity rating (Jameson
and Ring, 2000).
Local sensations such as muscle and knee pain during cycling exercise
are increased at lower cadences for similar power output. This is
probably associated with an increase in muscle force production required
at lower cadences. The variable intensity protocol in the present
study permitted subjects to alter the cadence by changing the pedalling
frequency and gear ratio throughout each trial. Since our participants
were not competitive cyclists and presented a significant increase
in cycling distance performance over the trials. It is probable that
adjustments in cadence and gear selection (anecdotal observations)
improved the cycling distance performance and reduced the intensity
of muscle pain amongst the trials.
|
| CONCLUSIONS |
The
present study provides evidence that the rating of muscle pain intensity
during exercise is attenuated with endurance cycling training. Furthermore,
the attenuation in muscle pain intensity with training is apparent
despite an increase in cycling distance performance. The decline in
muscle pain rating and increased cycling performance maybe associated
with adjustments in cadence and gear selection amongst the endurance
trials.
|
| ACKNOWLEDGMENTS |
| The
assistance of Nathan Serwach, Matthew Hilder, and Jack Cannon in facilitating
the collection and recording of data is gratefully acknowledged. |
| KEY
POINTS |
- Muscle
pain intensity rating was significantly reduced with three repeated
cycling endurance trials.
- Attenuation
in muscle pain intensity rating appeared at 50, 55, 60 mins into
exercise within the third trial.
- The
attenuation in muscle pain intensity with training is apparent
despite an increase in cycling distance performance.
- The
decline in muscle pain rating and increased cycling performance
may be associated with adjustment in cadence and gear selection
amongst the endurance trails.
|
| AUTHORS
BIOGRAPHY |
Peter
S. MICALOS
Employment: Lecturer, School of Human Movement, Charles
Sturt University, Bathurst, Australia
Degree: MEd
Research interests: Exercise induced analgesia
Email: pmicalos@csu.edu.au
|
|
Frank
E. MARINO
Degree: Associate Professor
Research interests: Physiological and neurological responses
to exercise in hot and cool conditions
Email: fmarino@csu.edu.au
|
|
Derek KAY
Degree: PhD
Research interests: Physiological and neurological responses
to exercise in the heat and the effects of hydration status.
Email: dkay@csu.edu.au
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