Laterality in Upper Limb Composition and Maximal
Isometric Strength of Elbow Joint ofBaseball Players
Yuichi Hirano* and Shigeki Ikegawa'*
Departmelrt of Sports Sciences, College of Arts and Sciences, University of Tokyo
Department of Physical Education, Japan Women's University

Abstrsct
The purpose of this study was to investigate the laterality in upper limb composition and maximal
isometric strength of elbow joint of baseball players. The professional basebalt ptayers (n = 8) and thehealthy male volunteers (n=10) served as the subjects. The cross-sectional areas of each tissue in upper

limb were measuled on both dominant and nondominant sides by the ultmsonic method. Also, themaximal isometdc strengths of both elbow extensiol and flexion were measuled for each subject.
Comparison of the two goups indicated that the basebalt group was distinguished from the controls
by significantly large corss-sectional area of the extenso! muscle in the dominant forearm. The closssectional alea of the flexor muscle was targer in the dominant forearm both of baseball players and ofcontrols. No sigdficant lateralities were observed in the cross-s€ctional a.reas in the other tissues(muscle, bone and fat) for the baseball group. Furthermore, for both groups, there were no significant
differences in the maximal isometric strengths of the elbow extersion and flexion between the domi-

nant and the nondominant limbs, It was concluded that the baseball players seemed to indicate theinfluence of taining on the muscle hypertrophy in the dominant forearm,
Key Words: baseball, laterality, limb composition, isometric strength

Intloduclion

It has been indicated that the closs-sectional area of muscle nolmally teflects its maximal isometric strength.T'lr'r2) The inoeas"s of cross-sectional alea and maximal isometric strength of themuscle submitted to strength training have aheady been confirmed.3,a,l3) Therefole, it is consideredthat when ar athlete is engaged in one kind of sports for a long time, which is adequate as a stimulus todevelop muscle hypertrophy, he selectively reveals the ircreases of cross-sectional area and maximal
isometdc strelgth of the muscle recruited in his activity. Itl case of tennis, tennfu players were dis.
tinguished from the controls by significantty increased isometric strangth of metacarpophalangeat joint
extension of the fingers on the dominant side.rT) But, there has been few inyestigations on the later-ality in limb composition of the athletes who use striking instrument in their sports activities.

In this study, baseball players were chosen as the subjects because they swing a bat and us€ theirTable , . Comparison of body height, body weight and %fat betweenbas€ballers and controls
helght(cln)welght(kg)baseballers(N=8)

1797■ 17● ホ780■ 63。 ■●11 16■ 387

contlols (N=10)

171 7 ■7 3594■ 57

11 87 ・t263%Fat(%)

Values are mean r SD.

'*p<0.01,'*,p<0.001

The Broiekl) equations werc used to predict %fat and LBM from body density
determined hydroststicaly.

dominant upper limb to throw a ball. It seems a worthwhile problem in baseball players to investigate
the laterality in upper limb composition and maximal isometric strenBth ol elbow joint,

Procedures

Eight professional baseball players, aged l9-24yr, served as the baseball group. They had no
symptom of exercise-induced pain. The control group was complised of l0 healthy male voluntee$,aged l8-20yr. All wele informed of the procedures alld purpose of this study. The charactedstics ofthe subjects studied ale given in Table l.

The crosgsectional area of upper limb tissue of the subject was measured by the ultrasonicapparatus (ALOKA, ECHO-VISION SSD-I20) connected with the circular compound scanner.?)
The 6070 distal point from the acromion for upper arm and the 30% distal ore irom the olecranon
for forearm were adopted as th'e point fo! the measurement of cross-sectional area. Dominant andnondominant limbs of each subject were alternately imme$ed in a water tark to get the cross-sectional
image. The 5MHz frequency of ultrasonic wave was selected to get a clear image on the screen. The
cross-sectiotrel areas of each tissue such as fat, muscle and bone were calculated from photogaphed
image by using a planimeter. The doss-sectional area of each muscle was anatomically classified into
two goups of the extensor and the flexor muscles.
The maximal isometric strengths of both elbow extension and flexion were measured on bothdominant and trondominant sides by means of a strain gauge transducer. Each subject seated on achat and put his upper alm on a specially designed ho zontal rest set above each side edge of the seat,and the forearm was half-plonated at 7Oo flexion in the elbow joint (full extension=Oo).

A paied t-test was used to compare the values obtahed from the dominant and the nondominant
upper timbs in all cases. Difference in laterality betwe€n the baseball and the control groups wastested for significance by ANCOVA. The 0.05 level of confidence was accepted as statistically significant for all statistical tasts. Data in the text and tables are preseflted as mean 1SD.

Results

The crosssectional areas of each tissue in the upper limb are presented in Table 2. The baseballgroup indicated significantly greater values ir the crosssectional areas of the extensor (p<0.01) andTeble

2. Cross-scctional areas ol esch ti$a in upper titnb
conttol groupbaseball 8loup

forearm

dominant

nondomfuunt

068

478■ 058
1711■ 2,4 s
2291■ 308903± 159

348■ 036
1474■ 246
1940■ 122。 ■715■ 146349■ 051 (cln')
1399■ 205
1790■ 172714■ 143

429■ 061
2460■ 416
1817± 244

365■ 050
1582■ 318
1473■ 196●
1218■ 400

364■ 076
1648■ 287
1346■ 246
1153■ 359

bone

4 81■

extensor m

18 75 ■191拿 拿

nexor m25 16■ 217●

fat

8 65

uplr"t arm tone

exte or m.
flexor m-fat■324

471 11041
2395■ 312
1841■ 287
1674■ 597

164411503

dominant

nondominant

I p<0.05, **p<0.01; difference between the dominant and the nofldominant limbs$ p<0.05; diflerence in laterality between the baseball and the control 8loups.

@f]]

(N)

dominant
nondominant

21Xl

extension

flexionbaseball group
F,S.

I

extension flexion
control group

Maximal isometlic atentth of.lbow joint

the flexo! (p(0.05) muscles in the dominant forearm than those in the noldominalt. Significant
lateralities were not consistently observed between the dominant and the nondominart upper limbs inthe other tissues for the baseball goup. The control group showed significantly geater values in thecross-sectional areas of the flexor muscle in the domiaant forearm (p(0.01) and upper arem (p<0.05).

Additionaly, the diffetence in the cross-sectional area of the extensor muscle between the dominant
and the nondominant forearm was gteater (p(0.05) for the baseball group than for the controls.
The maximal isometric strengths of the clbow extension and flexion for the baseball group averaged, in 224.1 129.2 N (meant SD) and 198.2 ! 25.7 N on the dominant side, zr.d 22O.5 i 34.8 N and

196.1 ! 22.8 N on the nondominant side, respectively. The coresponding values for the contlol
group were 2O1.2 ! 3'7.8 N and 190.8 t 30.2 N on the dominant side, and 202.1 ! 38.'7 N and 176.5 i
20.8 N on the nondominant side, lespectively (Figure l.) For both goups, there were no significant

23

differences in the maximal isometric sttengths of the elbow extension .nd flexion between thedominaot and the nondominart limbs.

Di!culrion
There was no sigrificant diffelence in %fat between the baseball and the control groups, althoughbody height and body weight for the baseball group wele significantly greater than those for thecontrcls (Table l). The value of Vofat for the baseball group (lt.l6 ! 3,'l%) werc approximately
similar to that of previous studies.2'5) The baseball goup in the present study seems to be replesentative of the chsracteristics of general baseball players.

It has been pointed out that when the dominant limb with a ball is accel€rated forward in spsce
during the pitching motion, the extensor muscle in the dominalt upper arm is notably active.E'10'r4)

It indicates the possibility of the hypertlophy in the extensor muscle. No significant difference,
however, was observed in the cross-sectional area of the extensor muscle between the dominant and thenoldominant upper alms for the baseball group (Table 2). And as a c4nsequence of the same amountof the extensoi muscle, there was also no significant difference in the maximal isometric strength ofthe elbow extension between both uppe! arms (Figure l). According to the comparative study between the little league$ and the professional baseball playe$, there was no signilicant difference
between them in the percentage of the crosesectional area of the triceps muscle to that of the whole
upper arm muscle.9) It might be considered that the strength exerted by the extenso! muscle in thedominant upper arm during the pitching molion was small as compared with the maximal isometricstrength of it, fot the elbow joint of the dominant limb was mpidly extended. It was also leported
that socce! playe$ did not indicated the increase in muscle strength of the knee extension by soccet
training alone.ls) The present results on the elbow extension seems to support the opinion that theactivity of ball game is inadequate for increase in maximal isometric strength measuled by regularstrength test.lE)

The baseball playeN were disthguished from the controls by significantly larger cross-sectional
area of the extensor muscle in the dominant forearm. This result is also supported by the previous
investigation that there was a strong corelationship between the wrist extension and throwing
speed.r6) Furtheremore, the basebalt players indicated targer cross-sectional area of the flexor muscle
in the dominant forcarm than that in the nondominant, although there was no significantly different
laterality in this area between both groups. As the angular velocities of the wrist extension and flexion
dudng the pitching motion are smaller than that of the elbow extension,s) it may be possible toconsider that the wrist joint owed the role for fixation of the hand against the forearm during thepitching motion, especiaUy during follow through movement. Another factor for this result thatshould be considered is that the baseball players swing a bat many times. Metacarpophalangeal joint
extension strength is reported to be significantly greater in the domhallt arm of tennis players.rT)
Similar to the tennis rac4uet, the mass of the baseball bat might be adequate to incrcas€ the crosssectional area and the maximal isometric strength of the peripheral muscle in the upper limb.

24
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