Vol.2, No.11, 1249-1254 (2010)
Copyright © 2010 SciRes. http://www.scirp.org/journal/HEALTH/
Openly accessible at
Comparison of strength values and laterality in various
muscle contractions between competitive swimmers
and untrained persons
Shinichi Demura1, Hiroki Aoki1, Yuta Yamamoto2, Shunsuke Yamaji3*
1Kanazawa University, Graduate school of Natural Science & Technology, Kanazawa, Japan;
2Kanazawa Gakuin High School, Kanazawa, Japan;
3University of Fukui, Faculty of Medical Sciences, Fukui, Japan; *Corresponding Author: yamaji@u-fukui.ac.jp.
Received 6 July 2010; revised 20 July 2010; accepted 2 August 2010.
Competitive swimmers may gain a specific train-
ing effect as the result of long term exercise in
the water. This study aimed to compare isomet-
ric, non-isokinetic and isokinetic muscle streng-
ths in competitive swimmers and untrained per-
sons. Twelve young male adults without exercise
experience for over three years and twelve swim-
mers with over 10 years of competitive swimming
experience performed various strength tests.
Non-isokinetic tests were evaluated using one
repetition of maximum half squat, vertical jump,
and drop jump. Isometric and isokinetic (60 and
180 deg/s) muscle strengths were measured by
both legs in knee extension and flexion. There
were no significant differences between non-
isokinetic and isometric muscle strengths of
both groups. On the other hand, all isokinetic
parameters in both angular velocities were sig-
nificantly larger in competitive swimmers. There
was significant laterality of isokinetic strength
in untrained persons, but not in competitive
swimmers. In addition, right and left differences
of isokinetic strength tended to be smaller in
competitive swimmers. In conclusion, competi-
tive swimmers tended to be superior only in
isokinetic strength, which is a similar muscle
contraction in the water, and have less right and
left differences.
Keywords: Lsokinetic Strength; Lsometric Strength;
Knee Extension and Flexion; Laterality
The exercise training effect depends largely on the
training method, i.e., training region, muscle contraction
property, and work load as indicated by the principle of
specificity of training [1]. Competitive swimmers gain a
specific training effect which differs from other athletes
as the water training environment requires nearly isoki-
netic muscle contraction [2,3].
Muscle contraction on dry land is unlikely to be com-
pletely isotonic in all ranges of motion. In a narrow
sense, the muscle tension in the latter output phase is
allowed to be smaller based on the acceleration produced
in the initial maximum output phase. However, in water,
maximum muscle tension is also required in the latter
output phase because the drag becomes loads in all
ranges of motion [4]. That is, it is possible that competi-
tive swimmers gain a training effect with superior mus-
cle strength exertion during isokinetic contraction or in
the latter range of motion as compared to other athletes
on dry land or untrained persons. On the other hand,
Taguchi [5] compared the eccentric and concentric mus-
cle strengths of competitive swimmers and untrained
persons and reported that the eccentric strength per body
mass and eccentric/concentric strength ratio were infe-
rior in swimmers. In addition, Tanaka and Swensen [6]
pointed out that the incremental increases of muscle
strength from traditional resistance training on dry land
contributed little to the improvement of competitive
swim performances and suggested that water training
should be more swim-specific.
In short, previous studies [5-7] have examined eccen-
tric and concentric muscle strengths of competitive
swimmers and the influence of resistance training on dry
land on swim performances. However they have not
sufficiently studied the isokinetic muscle strength mainly
used in water training.
Swimming is performed in either a supine or prone
posture with a bilaterally-symmetric motion and is in-
fluenced by buoyancy. In other words, it is nearly unaf-
fected by gravity and requires the same muscle exertion
S. Demura et al. / Health 2 (2010) 1249-1254
Copyright © 2010 SciRes. http://www.scirp.org/journal/HEALTH/Openly accessible at
of both the right and left extremities [8]. On the other
hand, most sports competitors on dry land in games in-
volving balls mostly use the dominant extremities. In
addition, behavior emphasizing the dominant extremity
is performed frequently in daily living [9]. The laterality
of muscle strength in competitive swimmers may be
lower than that in other dry land athletes or untrained
persons because they require the same muscle exertion
in both the right and left extremities. However, this pro
blem has not been thoroughly examined.
Some previous studies [5-7] hold a negative view of
resistance training on dry land for swimmers because the
muscle gains of swimmers differ from those of general
competitors on dry land. If so, swimmer-specific resis-
tance training protocols should be proposed. Moreover,
most competitors using dominant extremities on dry land
develop an imbalance of body alignment or injury [10].
If muscle output in swimmers’ extremities remains bal-
anced, swimming may play an important role in condi-
tioning training to correct an alignment imbalance.
This study aimed to compare isometric, non-isokinetic
and isokinetic muscle strengths of competitive swim-
mers and untrained persons.
2.1. Participants
A group of 12 male competitive swimmers, experi-
enced in competitive swimming 5 days a week for over a
decade (mean ± SD, age: 20.0 ± 1.4 years, height: 172.8
± 4.3 cm, body mass: 67.7 ± 6.6 kg) and a group of 12
male individuals who had not exercised for the past three
years (mean ± SD, age: 23.0 ± 0.6 years, height: 171.9 ±
3.2 cm, body mass: 64.6 ± 6.4 kg) participated in this
study. There were no significant differences of age, height,
and body mass between both groups. Participants received
an explanation of the aims and methods of this study and
signed an informed consent form. This study was appro-
ved by our University Committee on Human Research.
2.2. Measurements Procedures of Muscle
Strength Parameters
Muscle strength was evaluated from non-isokinetic
(one repetition of maximum half squat (1 RM half SQ),
vertical jump, and drop jump), isometric and isokinetic
knee extension and flexion muscle strength. Isometric
and isokinetic muscle strength were measured in both
the dominant and non-dominant legs. The dominant leg
was defined as the leg used to kick a ball.
2.3. Non-Isokinetic Muscle Strength
1) One repetition of maximum half squat (1 RM half
Regarding the non-isokinetic muscle strength, par-
ticipants performed one repetition of maximum half
squat (1 RM half SQ). A barbell was placed on a power
rack at about 10 cm below the participants’ shoulder
height at the beginning of the test. The participants posi-
tioned themselves under the barbell, stood up, stepped a
few steps back, squatted down (90 degree knee flexion)
and stood up. Their feet position and grip width were
self-selected. They placed the barbell on their upper tra-
pezius muscle immediately below C7. They started the
warm-up with sets of 1-5 repetitions with the bar only
(20 kg). They then added weight of 20-40 kg in each set
until the load became about 60% of the estimated 1 RM
and then added 5-10 kg until the load was 90% of the
estimated 1 RM. After completing these sets, the weight
was increased by 2.5 or 5 kg each set until their 1 RM
was determined. They were allowed to take as much rest
as needed between sets to minimize the effects of fa-
2) Vertical Jump
The distal vertical jump meter (Jump distal MD, TA-
KEI, Japan) was used to measure the participant’s verti-
cal jump height. Participants performed two counter-
movement vertical jumps with arm-swing movements,
and the higher value was used for statistical analysis.
3) Drop Jump
The distal vertical jump meter (Jump distal MD, TA-
KEI, Japan) was used to measure the participant’s verti-
cal jump height during the drop jump. Participants were
asked to step off a 40 cm box and jump immediately
after the landing, aiming to produce the maximum height
while minimizing ground contact time. During this jump
movement, their hands were kept on their hips. They
performed the drop jump twice, and the higher value was
used for statistical analysis.
2.4. Lsometric Muscle Strength
Isometric muscle maximum strength was measured at
a knee angle of 1.309 rad (75 degree) using an isokinetic
dynamometer (Cybex-325, Lumex, USA) at 0 degs-1.
The participants performed this movement twice, and the
larger value was used for statistical analysis.
2.5. Lsokinetic Muscle Strength
An isokinetic dynamometer (Cybex-325, Lumex, USA)
was used to measure isokinetic maximum strength. Peak
torque during knee extension and flexion at two angular
velocities, 60 degs-1 (five trials) and 180 degs-1 (thirty
trials) was measured as described previously [11]. The
largest value was adopted as the peak torque for each
angular velocity. In addition, the sum of total work in 30
trials was measured at180 degs-1.
S. Demura et al. / Health 2 (2010) 1249-1254
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2.6. Data Analysis
The mean differences of non-isokinetic muscle strength
parameters between the two groups were revealed with
the student’s t-test. Two-way repeated measures ANOVA
(groups [swimmers and untrained persons] × measures
[dominant and non dominant leg]) were used to compare
mean differences of isometric and isokinetic muscle
strength parameters. A Tukey HSD post-hoc test was
used to localize differences. In addition, the mean dif-
ference of abmodality between both legs was examined
with the student’s t-test. In all statistical analyses, the
0.05 level of significance was adopted.
There were no significant differences between non-
isokinetic muscle strengths for swimmers and untrained
individuals (Table 1).
For isometric knee extension and flexion, there were
no significant differences (Figure 1). On the other hand,
for isokinetic knee extension peak torque, there were
significant interactions in both angular velocities (60 deg
s-1: F1,22 = 9.45, P = 0.01, 180 degs-1: F1,22 = 4.49, P =
0.05) (Figure 2). In addition, there were significant
group effects in both angular velocities for isokinetic
knee flexion peak torque (60 degs-1: F1,22 = 5.20, P =
0.03, 180 degs-1: F1,22 = 12.65, P = 0.00) and the sum of
total work in both motions (Extension: F1,22 = 7.98, P =
0.01, Flexion: F1,22 = 4.40, P = 0.05) (Table 2). The
post-hoc test revealed that all isokinetic parameters were
significantly larger in the swimmer group and that peak
torques by the dominant leg for extension (60 and 180
deg/s) and flexion (60 deg/s) were larger in the untrained
persons group.
For abmodality between both legs in isometric pa-
rameters, there were no significant differences between
both groups. However, for isokinetic parameters, there
were significant differences between both groups in ex-
tension peak torque at both angular velocities and in
flexion total work (Table 3).
Muscle cross-sectional area, neural adaptations, and
the ratio of fast twitch fibers are the main determinants
of maximum muscle strength and power [12]. Of them,
the ratio of fast twitch fibers varies only slightly with
acquired factors, such as training. Therefore, resistance
training is conducted to improve other factors. Although
the improvement of these physiological factors enhances
strength performance, it is not always true that strength
performance in all contraction types (isometric, isoki-
Table 1. Non-isokinetic strengths in untraiened persons and competitive swimmers.
Untrained personsa Swimmersa
T(22) p ES
1RM half SQ (kg) 107.5 21.6 97.9 19.9 1.130 0.271 0.46
Vertical jump (cm) 59.5 4.0 60.4 5.3 0.478 0.638 0.20
Drop jump (cm) 55.6 5.2 56.2 3.5 0.320 0.752 0.13
Note: a: n = 12, M: mean, SD: Standard diviation, ES: Effect size
Table 2. Isometric and isokinetic strengths by dominant and non dominant legs in untrained persons and competitive swimmers.
Untrained persons (n = 12) Competitive swimmers (n = 12)
Dominant Non dominant Dominant Non dominant
Extension 216.3 40.4213.8 41.9234.0 41.6 230.1 41.9
Flexion 89.3 18.189.6 19.293.3 10.0 90.3 13.5
Isokinetic 60 deg/s
Extension (peak torque) 167.8 25.0150.8 33.2186.8 14.8 183.2 17.8
Flexion (peak torque) 103.3 20.393.6 21.9113.8 14.8 113.3 8.7
Isokinetic 180 deg/s
Extension (peak torque) 103.6 14.897.8 17.7121.0 15.0 118.9 16.3
Flexion (peak torque) 76.2 7.6 75.3 11.591.5 18.9 93.3 12.6
Extension (Sum of total work) 2554.8 432.02489.3395.92966.3340.7 3013.2486.6
Flexion (sum of total work) 1925.1 325.71912.3172.62148.3457.4 2252.3390.0
S. Demura et al. / Health 2 (2010) 1249-1254
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Table 3. The abmodality between both legs about isometric and isokinetic parameters.
Untrained personsCompetitive swimmers
Extension 14.912.617.315.3 0.41 0.687
Flexion 7.3 6.9 6.6 5.2 0.30 0.767
Isokinetic 60 deg/s
Extension (peak torque) 16.913.16.8 4.3 2.55 0.018*
Flexion (peak torque) 13.39.1 7.9 6.4 1.67 0.110
Isokinetic 180 deg/s
Extension (peak torque) 6.3 5.1 2.3 1.5 2.59 0.017*
Flexion (peak torque) 9.9 7.8 11.17.6 0.37 0.714
Extension (Sum of total work) 198.8138.4103.8100.5 1.93 0.067
Flexion (sum of total work) 265.2172.2118.3143.3 2.27 0.033*
*: p < 0.05, M: mean, SD: standard deviation.
Extension Flexion
Figure 1. Isometric strengths by dominant () and non dominant () leg during knee exten-
sion and flexion in untrained persons and competitive swimmers.
Isokinetic 60 deg /sIsokinetic 180 deg /s
Extension PT
Flexion PT
Extension PT
Flexion PT
Exte nsion
Total work
Flexio n
Total work
Figure 2. Isokinetic strengths by dominant () and non dominant () leg during knee exten-
sion and flexion in untrained persons and competitive swimmers. *: the peak torque was sig-
nificantly larger in dominant leg. †: the torque was significantly larger in competitive swim-
mers. U: untrained persons, S: competitive.
Openly accessible at
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netic, isotonic, and eccentric contractions) are enhanced
to the same degree [13]. In addition, the improvement
ofstrength performance based on cross-sectional area
may deteriorate swim performances because they are
determined by the relationship between the propulsion
produced by strength performance and passive drag [14].
It is recognized that the characteristic body shape of top
competitive swimmers (slight build) is different than that
of dry land athletes [15]. Therefore, competitive swim-
mers are a specific group that performs little resistance
training on dry land and trains mainly in water using
isokinetic contraction.
The improvement of strength performances depends
strongly on muscle contraction type, intensity, and con-
traction velocity during training as indicated by the prin-
ciple of specificity of training. Isokinetic contraction is
required for maximum muscle exertion throughout the
range of movement because the velocity of limb move-
ment is constant, and the resistance is equal to the ex-
erted muscle forces [16]. It was reported that isokinetic
training improves the isokinetic output, such as the peak
torque and the total work [17]. On the other hand, the
relationship between isometric and isotonic strengths is
very high, but these strengths are relatively low when
compared to isokinetic strength [18]. Aagaard et al. [19]
suggested that intraindividual differences of various
muscle contraction types may be affected by training
history or physical activity.
In this study, there were no significant differences of
non-isokinetic (1 RM half SQ, vertical jump, and drop
jump) and isometric knee extension and flexion
strengths between both groups. Vertical jump and drop
jump relate not only to lower limb strength and power,
but also to the stretch-shortening cycle (SSC). Taguchi
[5] reported that eccentric/concentric strength ratio was
inferior in competitive swimmers than in untrained per-
sons and suggested that competitive swimmers were
inferior in muscle output using the SSC. Swimming,
which is low intensity compared to muscle contraction
and has few eccentric contraction phases, uses little
muscle output during the SSC [5]. Therefore, competi-
tive swimmers are not considered to gain a training ef-
fect on SSC output.
However, all isokinetic strength parameters in both
angular velocities were superior in competitive swim-
mers. This suggests that maximum strength (peak torque)
and muscle endurance (the sum of total work) in isoki-
netic contraction may be improved by swimming. It is
unlikely that the difference of isokinetic strength in both
groups was caused by organic differences of muscle
(muscle fiber composition, cross-sectional area) because
there was no significant difference in isometric strength.
It may be the result of the lack of isokinetic contraction
in the daily activities of untrained persons.
Kovaleski et al. [20] reported that isokinetic training
enhanced the peak torque of isokinetic muscle output in
low, moderate, and high angular velocities, but the im-
provement of isotonic strength was more suitable in iso-
tonic training than in isokinetic training. This means that
the training method to improve muscle performances
depends largely on the aimed contraction type. Tanaka
and Swensen’s report [6] supported the above findings.
They found that resistance training on dry land for com-
petitive swimmers and untrained swimmers did not con-
tribute to the improvement of swimming performances,
despite substantially increasing upper body strength. In
addition, they also reported that combined swim and
swim-specific “in-water” resistance training programs
improved the swimming velocity up to 200 m in com-
petitive swimmers. Moreover, Neufer et al. [21] reported
that muscle strength was maintained after reducing
training volume or lack of training in competitive
swimmers for 4 weeks, but the ability to generate power
during swimming significantly decreased by 13.6 %.
In short, competitive swimmers are considered to have
improved isokinetic strength for swim performances
rather than non-isokinetic and isometric strengths. How-
ever, from the present results, we can not infer that
isokinetic strength training improves swimming per-
formances. This issue should be examined in further
We also compared the difference between dominant
and non-dominant legs in isometric and isokinetic
strengths. In untrained persons, isokinetic strength was
significantly larger in the dominant leg than in the
non-dominant leg. However, there was no significant
difference in competitive swimmers. Previous studies
[22,23] reported that the laterality of leg strength was
found not only in soccer players which use mostly the
dominant leg but also in untrained persons. It should be
noted that the laterality appeared only in isokinetic
strength of untrained persons. Because they were not
accustomed to isokinetic contraction, during which loads
are imposed maximally in all ranges of motion, the dif-
ference of the operability of the dominant and non-
dominant legs may have appeared as a difference of
force output.
Swimming performances do not place disproportion-
ate emphasis on an extremity and require similar muscle
exertion by both the right and left extremities. Therefore,
there is no laterality of muscle strength. Rather, laterality
of muscle strength may have a negative effect on swim-
ming performances.
Also in the comparison of abmodality between right
and left legs, competitive swimmers tended to decreased
isokinetic muscle performances than untrained persons.
S. Demura et al. / Health 2 (2010) 1249-1254
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Openly accessible at
Fine right and left balance of muscle strength is the re-
sult of swimming training.
In conclusion, competitive swimmers are superior to
untrained persons in isokinetic strength at 60 deg/s and
180 deg/s. There is a significant laterality of isokinetic
strength in untrained persons but not in competitive
swimmers. In addition, right and left differences of iso-
kinetic strength tended to be smaller in competitive
swimmers. These findings reflect the strength properties
of competitive swimmers gained in training.
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