Comparison of strength values and laterality in various muscle contractions between competitive swimmers and untrained persons

doi:10.4236/health.2010.211185

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Vol.2, No.11, 1249-1254 (2010)

doi:10.4236/health.2010.211185

Health

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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: [email protected].

Received 6 July 2010; revised 20 July 2010; accepted 2 August 2010.

ABSTRACT

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

1. INTRODUCTION

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

1250

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. METHODS

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

SQ).

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-

tigue.

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 deg･s-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 deg･s-1 (five trials) and 180 deg･s-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 deg･s-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.

3. RESULTS

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 deg･s-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 deg･s-1: F1,22 = 5.20, P =

0.03, 180 deg･s-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).

4. DISCUSSION

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

M SD M SD

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

M SD M SD M SD M SD

Isometric

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

M SD M SD

Isometric

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.

100

150

200

250

300

Extension Flexion

Untrained

Swimmer

(N)

Figure 1. Isometric strengths by dominant (■) and non dominant (□) leg during knee exten-

sion and flexion in untrained persons and competitive swimmers.

100

150

200

250

Isokinetic 60 deg /sIsokinetic 180 deg /s

†

††

†

Extension PT

Flexion PT

Extension PT

Flexion PT

Exte nsion

Total work

Flexio n

Total work

500

1000

1500

2000

2500

3000

3500

deg/s

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

S. Demura et al. / Health 2 (2010) 1249-1254

1253

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

studies.

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

1254

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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