Muscular Characteristics of the Dominant Upper Arm

in Japanese Little League Baseball Pitchers
Yuichi Hirano
Department of Sports Sciences, College of Arts and Sciences, University of Tokyo
Abstract
The purpose of this study v/as to investigate the characteristics of the triceps muscle in thedominant arm in little league baseball pitchers in comparison with that o{ professional baseball pitchersin Japan. The cross-sectional area and the maximum isometric strength of the triceps muscle and thepitched ball speed were measured on 6{teen little leaguers and five prolessional ones. Results were as
follows :1) The cross-sectional area of the triceps muscle in the little leaguers increased with the irrcrementof the body weight.

2) There was no significant difierence between the little leaguers and professional ofles in thepercentage of the cross-sectional area of the triceps muscle to that of the whole upper arm
muscle.

3) No signifrcant difference in the maximum isometric strcngth per unit cross-sectional area ofthe triceps muscle was observed between the little leaguers and the professional ones.

4) There was no significant correlatio[ between the pitched ball speed and the maximum
isometric strength of the triceps muscle.

5) The pitched ball speed per maximum isometric strength of the triceps muscle for the little
leaguers was significantly greater than that of the professional ones.

Key Words: baseball, little league, tricePs muscle, ball speed.
Introduction
Various reports with regard to the incidence of the throwing injury have been publishedo''z'1e).

And it has been said that excessive pitching places abnormal stress ort the shoulder and/or the elbow
and gradually leads to the throwing injury. Especially, clinical and roeotgenographic studies on thelittle league baseball pitchers(5,7,e,10) revealed that young and growing Pitchers tefld to sufier thisinjury. Therefore, with a preventive purpose against the throwing injury, it must have somemea[ing to iDvestigate physiological nature of pitching motion ifl youngsters.
The pitching motion consists of three phases such as cocking, acceleration and follow-through.
The acceleration phase is coosidered to be the most important in decidiog the speed ol the ball, because
the ball gets its speed owing to the drastic elbow exteflsion(rr'r6'r7). EMG analyses of the functionsof the muscles on the shoulder and the upper arm in pitching(1r'1'z) have also indicated that the ball
speed was dependent upon the magnitude of contraction of the tiiceps muscle.

In order to clarify the characteristics of the throwing arm of young pitchers, it was intended
to investigate the characteristics of the dominaot triceps muscle in Japanese little league baseball pitchersin comparisoo with that of Japanese professional ones.
Procedure

Subjecte: Filteen little leagte and five professional baseball pitchers in Japan served as the
subjects for this study. Preliminary descriptive data for each group are presented in Table 1. All
pitchers (right handed) were active as competitive baseball players aod had no symptom of exerciseinduced pain. After receiving a detailed explanation of the intent of the study, they submitted theirinformed consents for participation.
Muscle Cross-eectional Area: The length of the right upper arm of each subject, from theacromion to the olecranon, was measuld and the 60% distal point from the acromion was marked on

the skin. Each subject immersed his right arm perpendicularly irt a water tank to get the crosssectional image of his upper arm, which was obtained by use of the ultrasonic apparatus (ALOKA,
Echo-vision, SSD-120) connected with the circular compound scanner. The SMHz frequency ofultrasonic wave was selected to get a clear image of each muscle bundle and the image was photographedby a 35 mm camera. The cross-sectional area oI each muscle bundle was obtained from this photographby using a planimeter. In this study, the precentage of the cross-sectional area of the triceps muscle
to that of the whole muscle on the upper arm was calculated.

Maximum Isometric Str€ngth: The maximum isometric strength of the triceps muscle in theright arm was measured by means of strain gauge force transducer. Each subject seated on a chair
afld put his upper arm on a specially designed horizontal rest set above the right edge of the seat, andthe forearm was pronatd at 60o flexion in the elbow joint (full extension:0'). Additional stabilization
was achieved with a seat belt.

Pitched Ball Speed: Each sub.iect was asked to pitch the oficial basebalt (141.7-148.8g) withhis best efiort from the stretch position. His pitching motion was filmed by a 16mm cinecamera(Photosonics 16-l P, 200 frames/sec), which was located perpendicular to the line from pitchet's moundto home plate. The 6lm was analyzed with the aid of a film motion analyzer (SPORTIAS model-200,

Nac). Pitched ball speed was obtaifled by dividing the horizontal displacement(m) of the pitched ballfor 5 msec after ball release by the equivalent time(sec).
StetiEtics: Data were presented as ranges (lowest-highest) for the little leaguels and meanst
SDs for the professional olresr respectively. When the examioations were made on the relationships
between givel two measuremeats for little leaguers, the frirst order of partial cortelation by age wasused. Means and standard deviations were used to determine the differences between two groups. A
p value less than 0.05 was accepted as signiEcant,Table 1. Subjects' Data

協賠世vreight

Little League N:15

9‑12

130 6‑167 1

27 4‑62 4(range)Pro-Baseball N:5

22

1824

Pitchers
pitchers(kg)

804(Illean)BesultE

The cross-sectional areas of the whole muscle and the triceps muscle were 11.85-32.46cm' and6.30-17. 16cm'zfor the little leaguers, and 45.06i4.55cm'zand 26.04i4.62cm'z for the professional
ones, resp€ctively. Fig. 1 shows the relationships between the body weight and the cross-sectional areasof the triceps muscle and the whole muscle. Both cross-sectional areas for the little leaguers iocreased
tinearly with the increment of the body weight. Even if the age of the little leaguers was partialized,

both relatiooships were found to be significant (r,:.r: 738, .714). But, the percentage oI the crosssectional area of the triceps muscle to that of the whole muscle for the little leaguers resulted in aconstant value (55.5!3.S% (meantSD)) in sPite of the difieredce in the bodv vreight- This percent-

(cm2)

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80 (kg)Body WeightFlg. I Relationships between the body weight and the cross-iectional areas of thetriceps muscle and the whole muscle (large circles: Pro-Bareball Pitchers): i :[ : l : : : : :﹁Litue League
PitchersllXl(%):::::i::::三 ::::::::::::::::::::i:::::1■Ｊ

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Fig. 2 Percentage of the cross'sectional area oI the triceps duscle to thatof whole muscle

4

age was not significantly different when compared with the value of the professional ones (57,5+5.0%\(Fig. 2). This result indicates that the little leaguers have the same relative amount of the triceps
muscle as the prolessional on€s.

The maximum isometric stren6h (8.2-Z7.0kd of the triceps muscle for the little leaguen increased
in proportioo to the increment of the cross-sectional area oI the triceps muscle (Fig. 3). Io order toeliminate the factor of growing in the body, age-partialized correlation coefficient was calculated(ru.r:.590). The correlationship between the cross-sectional orea and the maximum isometric strengthof the triceps muscle was found to be significant (p<0.05). The professional ooes exhibited 29.1!4.3
kg in the maximum isometric strength of the triceps muscle. Although this value was greater than
thdt of the little leaguers, no significant difierence was {ound between the little leaguers (1.24!0.25
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Cross-Sectio;ral Area of the Triceps Muscle

Fig. 3 Relationship between the cross-sectional area and the maximum isometricstrength of the triceps muscle. (O Pro-Baseball Pitchers)

0.5

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Fig. 4 Maximum isometric sirength per unit cross-sectional area oI the triceps m$cle

5

Lg/cm'?) and the professional ones (1.20+0. 16 kg/cm'?) in the maximum isometric strength per unit
cross-sectional muscle area (Fig. 4).

Pnched ball speeds were 20.6-27.lmlsec for the little leaguers and 31.4t2.3m/sec for the
professional ones. Fig. 5 illustrates the relationship between the maximum isometric strength of thetriceps muscle and the pitched ball speed. Estimating from the first order of partial correlation (rrr,3:.401 ; n.s.), it would appear thar the pitched ball speed did not solely depend on the maximum
isometric strength o{ the triceps muscle. However, considering that the muscle strength produces theacceleration of body segruent and results in the iocrement in the pitched batl speed, it might suggestthat the pitched ball speed per maximum isometric strength of the triceps muscle could be used as anindex showing the contribution oI the muscle to the pitched ball speed. The value was significantly
greater for the little leaguers than for the professional ones (Fig. 6).

(m,/sec)
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35 (kg)luscleFig. 5 Relationship between the maximum isometric strength of the triceps
muscle and the pitched ball speed (O Pro-baseball Pitchers)
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Pitchers
Pro-Basebalt

pitchers

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Fig. 6 Pitched ball speed per maximum isometric strength oI the triceps muscle.

6

Discussion
Krogmano3) estimated the maturation age of 55 little league baseball players by means of the
X-ray 6lm of the hand aod concluded that little league baseball players were, in general, biologicallyadvanced. Using the crampton public hair index, Hale(6)also reported that 45.5Yo ol little league

matuler thafl
baseball players were postpuhscent and more pitchers and first basemen tened to be
pitchthe players at other positioos. Considering the agE tange of subjects irl this study, prepubescenters might be included. Therefore, the first order of partial correlation by age was used
the rclationships between the given two measured items'

to estimate

Fig. 1 shows the relationships between the body weight and the cross-sectional areas of thetliceps muscle and the whole upper alm muscle. The cross-sectional area of the tliceps muscle
perceotage of the crossexhibited a linear increase with the increment oI the body weight. But, theof the Career
sectional area of the triceps muscle to that of tbe whole muscle was constant regardless
(7-11
yrs)
resistancecyclingwith highin baseball (Fig. 2). Gifford(.), havirg trained prepubescent boys

(20 min/d, 3 ds/week) for 10 weeks, concluded that the training protocols were not sufficient to inducechanges in LBM. On the other hand, Von Dobeln and Eriksson(r3) reported

signiEcant chaoges in

exercisebody composition due to conditioning (boys, 11-13 yrs). There is a controversy regarding
and body compoeition in children and youth, because the dificulties are involving in the attempts toseparate the induced efiects of exercise from changes in the body composition

associated with growth

had the same relativeand mature. As to the result obtained in this study that the little leaguers
isneededto cladfy whether
investigation
further
professionallores,
amouot of the triceps muscle as thepitching practice may produce the hypertrophy in the triceps muscle'(9 and l1-year-old
Davies(3) investigated strength and mechanical properties of muscle in children
young adults, and reported that, if standardization was rnade Jor the muscle (plus bone)boys) andcross-sectional a!ea, the difference in muscle strength with respect to age

disappeared. The same result

was also obtained from the baseballers io this study'
pedegana et al.(15) investigated rhe relationship of upper extremity strength to throwing speed afld
concluded that the results o{ simple and multiple regression analysis showed arelationship between thestrenglh of the elbow extension and wrist extension movemerlt and throwing speed. Io this study, it
was found that, Ior the young baseballers, the pitched ball speed did not solely depend on the
maximum isometric streDgth of the triceps muscle. It is of no doubt thst the role of the trictps16), but, as the well-timed sequential
muscle io pitching is important in terms of the EMG analyses(r '2,
coordination of muscle activation supports the skilled pitching motion, single isometric muscular output

may oot have so strong a relationship with the pitched ball speed. In addition, Toyoshima et a1.(r6)reported that, in normal throwing, the angular velocity of the elbow extension was 31. 14 rad/sec. For
the professiooal major league pitchers, Pappas et al.(rr) measured 4595'/sec {or elbow extension. Quick

extersing motion of the elbow io pitchirg may be reducing in the relationship.
Overhand tbrowing pattern for children, in its all movement compooeots, leaches advanced levelby seventh grade(3'. So does the pitching motion of the little league baseball pitchers get to that ofthe professional ones in the early developmental stages' As pitched ball speed depends on both pitchingmotion and muscular outprlt, so the ball speed per maximum isometric strength of the triceps muscle

for the little leaguers may become greater than that of the professional ones. Therefore, it may be7suppos€d that the weight of a baseball gives a greater stress on the triceps muscle in the little leaguers.

These findings may provide a rationale for the warning derived from clinical and roentgenoSlaphic
studies on the little league baseball players.

Bcfererccs(1) Albright, J.A. et al.: Clinical Study of Baseball Pitchers: Correlation of lnjury to the Throwing
Arm with the Method of Delivery, Am. J. Sports Med., 6t 15 21, 1978-(2) Atwater, A. E. : Biomechanics of Overarm ThrowiDg Movements and of Thlowing Injuries. Exercise
and Sport Sciences Reviews, 7: 43-85, 1S79.

(3) Davies, C. T. M. : Strength and Mechanical Properties of Muscle in Children and Young Adults. Scand.
J. Sports Sci., ?: 11-15, 1985.

(4) Gifiord, P.: The Efiect of High Resistance and High Repetition Physical Activity on the Body
Composition of Prepubescent Boys. Unpublished Ph. D. dissertation, UDiyersity of lllinois, UrbanaChampaign, IL, 1973.
(5) Gugenheim, l.J. et al.r Little League Survey: the Houston Study. Am. J. Sports Med.,4:189-200,
1976.

(6) Hale, C. J. : Physiological Maturity of Little League Baseball Players. Res. Quart., 2? : 2?6- 4, 1956,(7) Hale, C.J.: lnjuries among ?71, 810 Little League Baseball Players. J. Sports Med. and Phys. Fitness,
1: 80-83, 1961.

(8) Halverson, L.E.: Development of the Overarm Throw: Movement and Ball Velocity Changes by
Seventh Grade. Res. Quart. for Exer. and Spoit, 53 r 198-205, 1982.

(9) Hang, Y. r Little League Elbow: A Clinical and Biomechanical Study. Biomechanics VIII-B: 70-85,
1983.

(10) Haosen, N. M, : Epiphyseal Changes in the Proximal Humerus o{ an Adolescent Baseball Pitcher. Am.
J. Sports Med., 10: 380-38{, 1982'(11) Jobe, F.W. et al.i Au EMG Analysis ol the Shoulder in Throwing and Pitching. A Preliminsly
Report. Am, J. Sports Med., 11 : 3-5, 1983-(12) Jobe, F. W. : An EMG Analysis of the Shoulder in Pitching. A Second Report. Am. J. Sports Med.,
12: 214-220, 1984.

(13) Krogman, W.M.: Maturation Age of 55 Boys in the Little League World Series, 1957. Res. Quarr.,
30: 54-56, 1959.

(14) Pappas, A.M. et al.r Biomechaoics oI Baseball Pitching. A Preliminary Report. Am. J. Sports Med.,
13t 2$-m, 19EE.

(15) PedeSana, L.R. et al.: The Relationship of Upper Extremity Strength to Throwing Speed. Ao. J,
Sports Med., 10: 352-354, 1982.

(16) Toyoshima, S. et al.: Contribution of the Body Parts to Thtowitrg Performance. Biomechanics IV:
169-174, 1974.

(17) Vaughn, R.E.: An Algorithm for Determining Arm Action during Overarm Baseball Pitchers. Biomechanics IX-B: 510-515, 1985.
(18) VonDobeln, W. and B.O. Eriksson: Physical Training, Maximum Oxygen Uptake and Dimensionsof the Oxigen Trausporting and Metaboliring Organs ir Boys 11 13 years of age. Acta Pediatr. Scand.,61 : 653-660, 1972.

(19) Wilson, F. D. et al.: Valgus Extension Overload in the PitchiDg Elbow. Am. J. Sports Med., 11:83-88, 1983.