Disability Type Influences Heart Rate
Response during Power Wheelchair Sport
J. P. BARFIELD
, LAURIE A. MALONE
, JILL M. COLLINS, and STEPHEN B. RUBLE
Emory & Henry College, Emory, VA;
Lakeshore Foundation, Birmingham, AL; and
Guidant Corporation, Saint Paul, MN
BARFIELD, J. P., L. A. MALONE, J. M. COLLINS, and S. B. RUBLE. Disability Type Influences Heart Rate Response during Power
Wheelchair Sport. Med. Sci. Sports Exerc., Vol. 37, No. 5, pp. 718 –723, 2005. Purpose: The purpose of this study was to determine
the influence of disability type on exercise response during power wheelchair competition. The secondary purpose was to determine
the extent to which heart rate responses during competition meet cardiorespiratory fitness training intensities for the general population.
Methods: Forty-eight athletes who had cerebral palsy (CP, N⫽31), spinal cord injury (SCI, N⫽10), or muscular dystrophy (MD,
N⫽7), and were competing in the 2003 Power Soccer National Tournament, volunteered to participate. Heart rate was recorded every
5 s throughout pregame and game conditions by Polar S610
monitors. Average heart rate (HR) values were determined for GAME
and RESPONSE (change score between GAME HR and pregame HR). The Kruskal–Wallis nonparametric test was used to determine
whether a significant difference among group medians existed on the dependent measure, RESPONSE (P⬍0.05). Results: A
significant difference on RESPONSE (P⬍0.05) existed among athletes with CP (29 bpm), SCI (17 bpm), and MD (26 bpm). The
median RESPONSE for athletes with CP was 12 bpm higher than athletes with SCI, and this difference was significant (P⬍0.01).
Further, 22 athletes with CP (71%), 5 athletes with MD (71%), and 1 athlete with SCI (10%) exceeded 55% of estimated HR
at least 30 min during competition. Conclusion: Disability type influences the heart rate response to power wheelchair sport, and may
affect the ability to sustain training intensities associated with fitness improvement. Key Words: PHYSICAL DISABILITY,
AEROBIC TRAINING, DISABLED SPORT, TARGET HEART RATE
Physical activity is an important lifestyle behavior for
individuals with physical disabilities (23). Specific to
this population, regular physical activity reduces risk
of secondary disease associated with disability (14), im-
proves lipid profiles (13), and increases functional capacity
(5). However, many individuals with physical disabilities do
not regularly engage in physical activity due to various
exercise barriers (18,27,29). Individuals with ambulation
limitations, such as those that rely on electric or power
wheelchairs, are most at risk of a sedentary lifestyle and
reduced opportunities to participate in physical activity.
Wheelchair sport opportunities are increasing for individuals
who rely on power wheelchairs for ambulation. Power wheel-
chair athletes include individuals with a variety of physical
disabilities, including arthrogryposis, cerebral palsy (CP), mus-
cular dystrophy (MD), spina bifida, and spinal cord injury
(SCI). Although the use of an electric wheelchair theoretically
equates the energy demand and limits exercise intensity for
participants, exercise responses to power wheelchair competi-
tion may vary due to mechanisms specific to disability type.
Several authors have documented higher energy expenditure
during low-intensity activity for children and adults with CP
compared with able-bodied controls (16,19,20,22,24,25). Un-
nithan and researchers (25) have documented that total body
work, or mechanical power output, explains 87% of variability
in oxygen cost of children with CP during submaximal walk-
ing. Inefficient movement patterns elicit greater work output
among individuals with CP, and wasteful movements or si-
multaneous contraction of opposing muscle groups may ex-
plain achievement of moderate exercise intensities (i.e., 3–7
METs) during light activity in this population (19 –20). Higher
energy expenditure during rest and low-intensity activity has
also been documented for children with MD compared with the
general population (3,26), but the causes are less understood.
Because balancing and body position adjustments among
power chair users may also elicit elevated work output com-
pared with the able-bodied population, it seems prudent to
document physiological response variations among power
wheelchair athletes to improve the understanding of acute and
chronic training outcomes that are disability specific.
To examine the influence of disability on power wheel-
chair activity responses, a pilot study was conducted on
three power wheelchair athletic teams. Heart rate (HR)
Address for correspondence: J. P. Barfield, Box 947, Emory & Henry
College, Emory, VA 24327; E-mail: firstname.lastname@example.org.
Submitted for publication June 2004.
Accepted for publication January 2005.
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Copyright © 2005 by the American College of Sports Medicine
responses of power soccer athletes were monitored before
and during power soccer scrimmages and official games.
Power soccer is similar to able-bodied soccer, except that
teams are limited to four players using power wheelchairs
(i.e., electric wheelchairs) to score an oversized ball on a
hard-court surface. Participants consisted of six athletes
with spastic CP and involvement in four limbs (i.e., quad-
riplegia). The comparison group consisted of four individ-
uals without CP (e.g., spina bifida and SCI). Mean HR for
pregame and game conditions as well as the change score
between game and pregame HR (RESPONSE) were mea-
sured. Visual inspection of the data substantiated that dis-
ability type influences HR response during power wheel-
chair sport (Fig. 1). The magnitude of the HR increase from
pregame conditions among athletes with CP, 46 ⫾15 bpm,
resembled an exercise intensity associated with physical
training in the general population; however, the HR increase
was not as high among individuals without cerebral palsy
(i.e., 15 ⫾4 bpm). Although factors such as environment
and anxiety can increase HR from resting conditions, a
sustained rise in HR during power wheelchair sport could
indicate achievement of a training threshold and associ-
ated cardiorespiratory fitness benefits for power wheel-
Despite an increase in health promotion literature specific
to individuals with disabilities, research is limited regarding
the physiological responses to exercise among individuals
with physical disabilities (18). Based on pilot study results
and the need for empirical investigations addressing severe
disability, the purpose of this study was to determine the
influence of disability type on HR response during compet-
itive power soccer competition. The secondary purpose was
to determine the extent to which HR responses among
individuals with various physical disabilities meet intensity
recommendations for the general population that elicit car-
diorespiratory fitness benefits. Due to the elevated work
output associated with involuntary movement, our hy-
pothesis was that athletes with CP would demonstrate a
significantly greater HR response during competition
than athletes with alternative disabilities due to disabili-
Participants. Power soccer players participating in the
2003 National Power Soccer Tournament were recruited to
participate in a nonrandomized pretest posttest design. In-
dividuals with CP (N⫽31), SCI (N⫽10), and MD (N⫽
7) volunteered to participate. Athletes with CP reported
spastic, ataxic, or mixed symptoms. Nine athletes with SCI
had injuries ranging from level C4 to C7. One athlete had a
complete injury at the T7 level. Initial recruitment efforts
were made through team coaches, and a project description
was provided to all teams before competition. Methods were
approved by institutional review for both pilot and main
study participants. Pilot data were collected approximately 4
months before the national tournament, but were not in-
cluded in the study sample. Consent was obtained from all
athletes and from parents of those athletes who were under
18 yr of age.
Groups consisted of athletes with CP, MD, and SCI.
Participants with CP were delimited to involvement in all
four limbs (i.e., quadriplegia). Athletes with MD and SCI
were delimited to individuals using power wheelchairs dur-
ing competition. Because variability across disability type
may influence physical responses to activity, secondary
analyses were conducted on experimental groups that were
further delimited based on common symptoms. The sub-
sample consisted of athletes with spastic CP (N⫽13) and
athletes with cervical spinal injuries (N⫽9). No further
delimitations were applied to individuals with MD.
Instrument. Polar S610
HR monitors (Polar Electro,
Inc., Woodbury, NY) were used to record all HR data. The
model enables HR to be measured at intervals of 5,
15, or 60 s, and data to be stored and downloaded. The
has a unique receiver for each transmitter and
prevents multiple unit interference. The investigators fitted
monitors to participants before game activities and attached
the receiver to either the subject’s wrist or armrest.
Procedures. Heart rate was recorded every 5 s through-
out pregame and game conditions, and later downloaded.
Data collection started approximately 10 min before sched-
uled warm-ups and occurred throughout the duration of each
tournament match. Data were collected from two to six
participants during each match, and visual observation of
matches was used to classify scores into the appropriate
category: PRE (lowest 5-s HR before team warm-ups),
GAME (average HR during the match), PEAK (highest 5-s
HR during competition), RANGE (difference score between
PRE and PEAK HR), and RESPONSE (difference score
between mean GAME and PRE HR). Data collection during
GAME conditions occurred over two 25-min halves, total-
ing 50 min. Although the HR instrument is intended to
prevent multiple unit interference, all downloaded data were
visually screened to ensure that scores were consistent and
not affected by extremes due to electrical malfunction (e.g.,
PEAK scores did not exceed maximum predicted values,
PEAK scores were within 5 bpm of subsequent high score).
Nongame activities (e.g., time outs, half time) were ex-
cluded from data analysis.
FIGURE 1—Individual HR differences from pregame to game condi-
POWER WHEELCHAIR SPORT Medicine & Science in Sports & Exercise姞
Analysis. Based on the Levene test, data did not meet
homogeneity of variance assumptions for ANOVA. There-
fore, to determine the effect of disability type on exercise
response during power soccer competition, the Kruskal–
Wallis one-way analysis of variance by ranks test ((21), pp.
397– 410, represented by the symbol H) was conducted on
the dependent measure, RESPONSE, to determine whether
a significant difference existed among medians for athletes
with CP, SCI, and MD (P⬍0.05). Power analyses, based
on pilot study results, were conducted to ensure adequate
sample size. Using the sample size estimate procedure sug-
gested by Cohen ((4), pp. 380 –390), we concluded that six
participants per group, in combination with the documented
effect size (d⫽2.57), should result in a power greater than
0.80. The power estimate is consistent with an observed
power of 0.89 in the pilot study derived from the general
linear model. The effect size, d, indicates that the RE-
SPONSE for athletes with CP was approximately 2.5 stan-
dard deviations greater than the RESPONSE for athletes
without CP. This index is computed by dividing the differ-
ence score between group means by the pooled standard
deviation ((4), pp. 20 –26). Mann–Whitney U post hoc com-
parisons between groups were conducted after a significant
difference ((21), pp. 181–194). Because Type I error can be
inflated by performing multiple statistical tests, the Dunn–
Bonferroni adjustment was made to experiment-wide alpha
reducing each post hoc comparison to an alpha level of 0.01
(6). An additional Kruskal–Wallis analysis was conducted
to determine whether a significant median difference existed
among athletes with spastic CP, cervical SCI, or MD (P⬍
Current American College of Sports Medicine (ACSM)
recommendations indicate that aerobic exercise ⱖ55%
(i.e., 4.8 METs for young adults) elicits improve-
ment in cardiorespiratory fitness in low-fit individuals (1).
To determine the extent to which HR responses meet ACSM
intensity recommendations, frequencies were conducted on
GAME HR to determine the number of participants that
averaged 55% of predicted HR
for 30 min during com-
petition. Also, GAME HR was used to estimate MET values
sustained during activity from four regression equations
appropriate for the current sample (i.e., children with CP,
adults with CP, children without CP, and adults without
CP). The regression equations for children were developed
on individuals aged 7–17 yr (19), whereas the adult equa-
tions were developed on individuals 18 yr and older (22).
Because participants ranged in age from 8 to 55 yr, partic-
ipant age and disability type dictated the regression equation
selected. All analyses were conducted with SPSS 11.0 (Chi-
Athletes with SCI (mean ⫽32.2 ⫾12.8 yr) and CP (mean
⫽28.4 ⫾11.5) were significantly older (t⫽3.35, df ⫽45,
P⬍0.05) than athletes with MD (mean ⫽14.1 ⫾2.9).
Heart rate increased from PRE conditions across all groups,
and descriptive statistics are presented in Tables 1 and 2 for
the entire sample and subsample, respectively. A significant
difference on RESPONSE existed among athletes with CP,
SCI, and MD (H⫽10.99, df ⫽2, P⬍0.05) with an
observed power of 0.90. This power statistic is based on the
general linear model, and actual power is lower for non-
parametric tests (i.e., Kruskal–Wallis). However, power of
the one-way analysis by ranks approximates the parametric
Ftest (21). The median RESPONSE for athletes with CP
was 12 bpm higher than athletes with SCI. This post hoc
comparison was significant (U⫽49.0, df ⫽1, P⬍0.01)
and represented a large effect (d⫽1.35). No additional post
hoc comparisons were significant; however, the effect sizes
between disability groups were noteworthy. A large effect
existed between MD and SCI (d⫽1.12), and a medium
effect existed between CP and MD (d⫽0.52). It is not
surprising that these group differences were not statistically
significant. Sample size estimates were based on distinct
disability group responses during the pilot study, but greater
functional overlap exists in the current sample (i.e., partic-
ipants from different groups were able to demonstrate sim-
TABLE 2. Heart rate responses (bpm) to power soccer competition among athletes
with spastic CP, cervical SCI, and MD.
CP (Nⴝ13) SCI (Nⴝ9) MD (Nⴝ7)
Mean 86 68 89
Median 88 70 89
SD 17 14 12
Range 63–121 54–99 74–109
Mean 119 87 115
Median 123 83 120
SD 21 15 12
Range 75–148 70–115 99–129
Mean 150 118 152
Median 154 116 148
SD 27 22 21
Range 89–186 91–151 122–189
Mean 33 19 26
Median 32 17 26
SD 14 6 8
Range 9–60 10–32 15–37
Data reflect delimited sample responses.
TABLE 1. Heart rate responses (bpm) during power soccer competition for athletes
with CP, SCI, and MD.
CP (Nⴝ31) SCI (Nⴝ10) MD (Nⴝ7)
Mean 88 69 89
Median 90 71 89
SD 15 13 12
Range 63–121 54–99 74–109
Mean 120 87 115
Median 117 86 120
SD 19 14 12
Range 75–154 70–115 99–129
Mean 154 118 152
Median 154 117 148
SD 23 21 21
Range 89–206 91–151 122–189
Mean 32 19 26
Median 29 17 26
SD 13 6 8
Range 8–60 10–32 15–37
Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
ilar limb and trunk function); therefore, power for post hoc
comparisons is probably lacking.
A significant median difference on RESPONSE existed
among athletes with spastic CP, cervical SCI, and MD (H⫽
7.91, df ⫽2, P⬍0.05) with an observed power of 0.85.
Athletes with spastic CP demonstrated a median RE-
SPONSE score 15 bpm higher than athletes with cervical
SCI. This post hoc comparison was significant (U⫽20.0,
df ⫽1, P⬍0.01) and represented a large effect (d⫽1.35).
A large effect existed between MD and cervical SCI (d⫽
1.06) and a medium effect existed between spastic CP and
MD (d⫽0.60), although these post hoc comparisons were
Twenty-two athletes with CP (71%) exceeded a cardio-
respiratory fitness training threshold for a minimum of 30
min despite use of a power wheelchair for competition (i.e.,
predicted). Nineteen of these 22 athletes
exceeded this threshold for the entire 50-min competition
and specific types of CP (e.g., spastic, mixed) did not
distinguish responders from nonresponders. Based on
GAME HR, athletes with CP averaged an exercise intensity
of 4.2 METs during competition. Five athletes with MD
(71%) exceeded 55% HR
for 30 min. Based on the
prediction equation for children without CP, athletes with
MD averaged 3.8 METs during competition. One athlete
with cervical SCI (10%) surpassed 55% HR
for a min-
imum of 30 min.
Disability type influences the HR of athletes during
power soccer competition (Fig. 2). Findings from the cur-
rent study reveal higher HR responses for athletes with CP
than athletes with SCI, potentially suggesting increased
activity demands for athletes with CP compared with SCI
during power wheelchair sport. Athletes with CP reached
and maintained higher HR intensities during competition
than athletes with SCI, as indicated by PEAK, GAME, and
RESPONSE scores. Results were similar for athletes delim-
ited into subsample groups based on symptoms. Responses
for athletes with spastic CP were reflective of athletes with
CP as a whole (i.e., spastic, athetoid, and mixed), indicating
that type of CP may not prohibit an increased HR response
to activity. These findings have important implications rel-
ative to the understanding of acute and chronic physiolog-
ical adaptations to disability sport.
The secondary purpose of the study was to determine the
extent to which competition heart rate met exercise intensity
recommendations for cardiorespiratory fitness. The ACSM
promotes that a training intensity of 55% HR
to elicit improvement in fitness for the general population
(1). Seventy-one percent of athletes with CP and MD ex-
ceeded this threshold for 30 min during competition. GAME
intensity ranged from 3.5 to 6.9 METs for athletes who
surpassed the HR criterion (mean
⫽4.9 ⫾1.0; mean
⫽4.4 ⫾0.5). GAME intensity ranged from 1.0 to 3.2 METs
for athletes that did not meet the target HR criterion
⫽2.4 ⫾0.7; mean
⫽2.3 ⫾0.1). Maximal HR
among individuals with complete cervical SCI typically
does not exceed 120 bpm due to sympathetic nervous sys-
tem impairment, and therefore predicted heart rate values
based on age are inappropriate. However, training intensi-
ties from 30 to 80% heart rate reserve among individuals
with quadriplegia may approximate 50 – 85% in the general
population (12). If the lower threshold is viable, eight of the
nine participants with cervical SCI exceeded this threshold
based on PRE, PEAK, and GAME HR.
The efficacy of ACSM training recommendations for
individuals with CP, SCI, and MD has been documented (7).
Regular training at moderate intensities improves submaxi-
mal exercise efficiency, improves maximal power output
and peak aerobic power, and reduces functional decline due
to inactivity in study populations ((7), pp. 237–294). Al-
though fewer longitudinal training studies for individuals
with physical disabilities are present in the literature com-
pared with the able-bodied population, empirical evidence
supports the use of these guidelines. Training at 135 bpm
over a 9-month period resulted in a 35% aerobic
capacity increase among children with CP (28). The current
participants were able to reach and sustain this intensity,
indicating the ability to obtain significant functional gains
through competition. The current findings also support the
use of ACSM intensity guidelines for individuals with CP
and MD based on the ability of GAME HR to distinguish
between individuals that did or did not maintain moderate-
intensity MET values. Despite the inability of all partici-
pants to sustain a training intensity, it is important to doc-
ument the ability of power wheelchair athletes to reach
training thresholds associated with important health benefits
through disability sport.
PEAK HR values obtained in the current study on athletes
with quadriplegic CP were similar to peak HR values re-
FIGURE 2—Heart rate response variability by disability. RESPONSE
scores represent the difference score between GAME and PRE (bpm).
This variable represents the increase in HR from pregame conditions.
Box plots represent the 25th to 75th percentile of RESPONSE scores.
The median score is denoted by the single horizontal line within the
box, and high/low scores are denoted by lines above and below the box,
respectively. An outlier is represented by the symbol X.
POWER WHEELCHAIR SPORT Medicine & Science in Sports & Exercise姞
ported among non–power wheelchair users with CP. Tobi-
matsu and colleagues (22) investigated the cardiorespiratory
responses to arm ergometry in 12 men with CP. Five indi-
viduals were community ambulators and seven were manual
wheelchair users. The mean peak HR for participants (spas-
tic, athetotic, and ataxic symptoms) was 154 bpm, identical
to the current study. Unnithan and colleagues (24) re-
ported a mean HR of 142 bpm at 90% of the fastest
walking speed among nine children with spastic CP
(seven with diplegia), and Rose and colleagues (19) re-
ported a mean HR of 160 bpm at maximum walking speed
in a similar sample. A HR of 154 bpm was reported as the
anaerobic threshold in one group of boys with spastic CP
that used elbow crutches (15), and the ability of athletes
to reach this intensity reinforces the possibility of a
training effect during power wheelchair sport.
Despite similar PEAK HR responses to non–power
wheelchair users, RESPONSE scores in the current sample
were lower than HR increases reported in samples with
diplegia and hemiplegia that performed continuous exercise.
Unnithan and colleagues (24) reported an increase of 56
bpm from rest to 90% of the fastest walking speed. This
increase is approximately 20 bpm higher than in the current
study (Table 1). Rose and associates (19) reported a 69-bpm
increase from rest to the fastest walking speed in four
children with hemiplegia and nine with diplegia. This re-
sponse was almost identical to a follow-up study that in-
cluded the difference between resting HR and the most
economical walking speed (20). Within the literature, To-
bimatsu and colleagues (22) reported the highest increase in
HR (74 bpm) from rest to peak physical working capacity on
an arm ergometer. Important to note, the current study
design necessitated the use of pregame HR values rather
than true resting HR to determine RESPONSE. Because net
increases in HR are typically evaluated by the change from
true resting conditions, it is possible that RESPONSE is
actually underestimated in the current study.
Our findings are consistent with previous studies that
documented increased heart rate and energy expenditure
among individuals with CP during various forms of ambu-
lation (3,9,17,19,20,24,25). Both the current findings and
literature support that power wheelchair exercise responses,
and therefore benefits, may be disability specific. Unnithan
et al. (24) revealed that simultaneous contraction of agonist
and antagonist muscles, or “cocontraction,” contributes to a
higher energy cost among individuals with CP. Use of an
electric wheelchair would not prevent cocontraction from
occurring, and therefore would not prevent elevated energy
expenditure during competition. It seems reasonable that in
an effort to balance and position oneself in a power wheel-
chair, energy expenditure and HR are higher than would be
expected due to mechanisms specific to CP.
Different mechanisms may explain the acute response
among individuals with spinal cord injuries. Figoni (8)
noted that oxygen extraction is greater among individuals
with spinal cord injuries than the able-bodied population.
Because exercise performance does not appear to be limited
by central factors such as reduced maximal stroke volume
(11), compensatory mechanisms such as greater oxygen
extraction by working muscles may explain the ability of
athletes with SCI to reach a training threshold. Specifically,
Hooker and Wells (10) documented that a training intensity
of 50% HR
resulted in a 10% increase in peak aerobic
capacity for an individual with a cervical SCI injury. If
minimal overload thresholds exist for individuals with
severe physical disabilities, power wheelchair sport may
provide a meaningful physical activity for individuals
Few researchers have addressed the acute responses of
exercise among individuals with MD. Increased energy ex-
penditure has been documented for a variety of muscular
dystrophies, and it seems plausible that energy costs are
greater due to muscle weakness (3). High energy costs may
also contribute to muscle deterioration (26). Individuals
with MD demonstrate autonomic dysfunction that worsens
over time (30), resulting from a reduction in parasympa-
thetic activity, accompanied by an increase in sympathetic
activity. Coupled, this mechanism results in sympathetic
overdrive and likely blunts heart rate response to mild and
moderate activity due to desensitization of
receptors. In heart failure, another condition in which sym-
pathetic overdrive exists,
-receptors downregulate to pro-
tect cardiac myocytes from harmful adrenergic stimulation
(2). Thus, it seems plausible that a similar physiological
adaptation may occur in individuals with muscular dystro-
phy. However, further study relating to physical activity
responses is needed in this population.
The major limitation of the current study is nonassess-
ment of endocrine influences on heart rate responses. It is
important to determine the extent that cardiac acceleration is
driven by psychological arousal. Stress in the current sample
of athletes with CP and MD was similar to competition
responses of able-bodied athletes. Heart rate increased be-
fore the start of competition, continued to increase at the
onset of competition, and incrementally increased during
competition before reaching a plateau. Figure 3 provides a
FIGURE 3—Heart rate responses (HR) for an athlete with CP, SCI,
and MD. The graph is a smoothed representation of HR scores for
three athletes collected every 5 s across the entire data collection
period. Competition started at the 5th minute, half time started at the
30th minute, the second half started at the 35th minute, and play
concluded at the 60th minute.
Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
visual representation of HR consistency across competition.
The stress response was distinct in the sample of athletes
with spinal cord injury. Unlike changes associated with
exercise, heart rate decreased at the onset of competition,
and continued to decline during competition until reaching
a plateau. A variety of stressors can cause a temporary rise
in HR (e.g., anxiety, temperature). However, the neutral
climate environment, consistent elevation of responses, and
consistency of results with pilot findings leads one to hy-
pothesize that exercise intensity was the predominant stim-
ulus of HR changes. Nonetheless, future investigations
should control for nonactivity influences on HR by utilizing
a repeated measures design to compare competition re-
sponses to observational responses.
In conclusion, disability type influences acute HR re-
sponse to power wheelchair sport. Athletes with CP dem-
onstrated higher heart rate responses during competition
than athletes with SCI or MD, and 71% of athletes with CP
and MD were able to sustain a training intensity associated
with improved cardiorespiratory fitness in the general pop-
ulation. Further, 88% of athletes with cervical SCI exceeded
adjusted HR intensities reflective of moderate training.
Findings from the current study substantiate the importance
of training studies on power wheelchair sport and associated
acute and chronic adaptations that may occur through dis-
The authors thank the 2003 National Power Soccer Tournament
athletes and organizing committee for their participation, and Ken
Linna for assistance with figures.
Equipment funding was made possible through Lakeshore
Results of the present study do not represent endorsement for
any products and/or services.
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