Genetic factors in the tissue compositionof human limbs
Tetsuo Fukunaga
Akif umi Matsuo
Nagahiko Adachi
Department of SPorts Sciences
College of Arts and Sciences
University of TokYo

ABSTRACT
Monozygotic twins of 4 pairs at 16 years (boy) participated as experimental subjects. The cross_sectional
area of tissues such as muscle, fat and bone in {orearm, upper arm, leg and thigh were measured by means ofultrasonic method. The maximum isometric strength of flexors and extensors at the three joints of elbow,
knee and ankle were measured by means of strain gauge force transducers. The intra-pair difference (lD) in
subcuraneous fat were t9-37fu, whlch irdiczred higher value than those in the bone (8-16%) and the muscle(z z%). h consideration of ID in the tissue composition for dizygotic tuins which previously reported(Ohtsuki, f976), the interindividual variations in bone mav only be ascrib€d to genetic difference'

Xeluortls: Cross'seclif al ared of tissue: Identical ttuin; Ultldso"ic 'nedsureme'ht
Human limts (forearm, upper arm, leg and thigh) are mainly composed o{ tissues suc}r as bone,fat, blood vessels, nerve ancl connective tissue. It is previously reported that crms'sectional areas ofmuscle, fat and bone closely related to the muscle functions such as strength and power and the mus'culartraining (Fukunaga, 1976). From biological, physiological and also educational lroints of view,
it is important to knolv the hereclity and environment affect aflect on the composition and muscle
strength. From acomparison of intrapair differences between identical and non'identical twins, in it
possible to <letermine that ohenotypic variability in identical twins is due solely to envilonmental agents, rvhereas that in non-identical twins is due to both genetic fluctuations and extragenetic influeces.

The purpose of the present study was to observe the e{{ect of heredity on the tissue composition
and the muscle strength in human limbs.

METEOD
Male monozygotic twins of 4pairs at 16yls participated as experimental subjects' Their zygosity
was determined in a manner previously descrived (Inoue, 1962)'
The cross'sectional areas oI tissues of tissues such as muscle, fat and bone were measured byof ultrasonic method (SS-120, ECHO-VISION, ALoKA, JAPAN)' The lrequencv of the ulmeans

alongttasonic wave was chosen to be 5 MHZ. The subjects immersed his arm or leg pependicularlyaroundthe central axis of a water tank. The scanner, oscillating in a range of 60 degrees circulates

18

the tank is about 30s and produces an image of a cross'section of the arm, lcg and thigh respctively,on the specially designed oscill<xcope rvhich is photographerl Ly mcans of a 35 mm camera. A tipicalultrasonic plrotogr;rph oI the leg and thigh was presenterl irr Fig. 1. The photograph was traced andplanimetric values were obtained from the three tissues, rvhich were tllen converted into actual crosssecsional areas by the calibrated formula.

The maximum isometric strength of flexors and extensors at the thtee joints oI elbow, knee andankle were measured bymeans of strain gauge force transducers. 'lhe subject was seated in a speciallydesigned chair and isometric muscle stre gth was mcasured in the elbow joiut llexed at 90", the knee

at 1100 ancl the arkle at 90o, respcctively. Three trials of maximum effort for about S-sec durationcach wcre gir,cn and the highest value was used Ior furthcr aualysis.

RESULTS
Cross-secticual pictures of leg and thihg of twin A and B were shown in Fig. 1. From theseEZ

Twin A

Twin B
LegFigure I

Ultrasonic cross-sectional .\,iew of human leg and thigh.

Table I

Body height, weight and isometric muscle strength ot
monozysotic t$ins. (m + s. d. )vin Arwin B

1715± 99

1710 ■ 91

63 6 ± 4 960 8 ± 7 8Knee extension69 4 ± 4 568 4 ±

7 3flexion
Planter llexion
Dorsal flexion
Elboiv extension

26 7 ■ 0 629 1 ■

6 2124 0 ■ 15 4120 9 ■ 21 4
25 0 ± 1 5T、Body Height (cm)Body Weight (ke)Muscle strens{h (ks)

24 7 ± 3 7217±
185±{lerion

30

T面 nA

I20104305

19 5 ±3 2179±20nBT
01020― ― 一―￢― ―――― ―――
T―― ―― ―「Q)
30

Ex1120―――――――――￢― ―――――― ―T―― ―――― ――――「―DFPF

Fisure 2 Nluscle strensth at elbo\v, knee and ankle joints inmonozysotic tNins. (In a s. d. )llx : Extension

Fl: Flexion
DF : Dorsl {lexion

PF: Planler flexion――￨Toble 2 Cross-sectional areas of shole section, fat, bone snd
muscle in the human limbs.
Cross-sectional

area (cm,)

T、 in AT、 、in B

ヽVh。 lc

47 9 ± 3 1

44 8 ± 5 5Fat2703

10 1 ■

2 4BOne119±39■Musclc32 5 ±

1 940±
313±0736

ヽVhole

51 0 ± 7 2

46 6 ±

4 6Fat157± 59
36 ± 02319± 36125±39±4405

30 2 ± 2 6WhOle

1101 ■ 81

104 3 ■ 11 6

Fat

27 4 ■

24 3 ± 3 7

BOnc

109± 08

10 6 ± 0 5

ヽ4uscle74 2 ■

5 7

70 1 ± 9 8

ヽVhole187 1 ± 13 0

178 0 ± 19 3

Fat

47 4 ± 14 4

39 0 ± 10 4

BOne

71

FOrearm

Upper arm

Boneヽ4uscle

Leg6 3Thigh03±77±

133 6 ± 9 7

ヽ4uscleTable !

Intra-pair differences in height, s'eightand muscle strengths.

(%)

Body Hetht
Body weighr

M蹴ごi鰍

extension
Planter Ilexion
Dorsal flerionKnee

10 47IA.lt

1 I 7お4f0.3

I

11.8

IIrs. s5. 02

flexionextensions. oz

intra l,air differcncc (ll))‐ T‖ 韓杵 Ⅷ2′19132 8 ± 9 4L×Ю0

Twin AI

Twin B
(市 )

(cば )

150

100

50050

100

1050510150

WHOLE

15Fignre 3

Cross-sectional areas of ihe whole section, fat, muscle and bone.

FA: Forearm
UA: Uprrr arml,E: t-eg
TH : Thieh

Table 4 lntra.pair dilferences in tissue composiiion.
(%)

ｃｅ ︲︲ｃ︒
ｓｈｕＷ﹄恥ＭForearm

Upper arm

Lcg

Thigh113

13 57 55

7 3426 136 918 929 57 83

12 07 99

16 77 31

6 35

6 47

1 55

22pictures it was observed thats hapes of twin A \Mere similar to those of twin B, while

subcutaneous

fats differed in the pair.

In Tab. 1 and rab. 2 mean body height, weight and isometric strength, and cross-sectional areasof tissues were indicated with standard deviatioos. cro*s-sectional areas of the wholg fat, muscle andbone tissues were shown in Fig. 3. The whole sectional area indicated almost the same value of abouti, tl,e leg and the thigh were about 2 tirnes ancl 3. 3 timesof that in the arm area, respectively. Fat .rea indicated higher values in the upper arm than in theSOcm'z in forearm and upper arm, and those

Iorearm, and higher in the than in the leg. F.t area in the thigh was about 40cm, and it rvas about 4times of fore.rm fat. Thigh muscle areas was ab.ut 130cm, and it was 1.9 times of leg muscle area.
cross-sectional irrea o{ bones in forearm consists of ulna and radius, and in leg tibia and fibula. Bonearea indicated almoat tLe s.ame values of alxrut 4cm, in both forearm and ul)pcr arm. Bone area in leg
rvas about 10cm,, which tvas 1.4times of th:rt of rhigh.

Inirapr irｈｑ却s0%
● ☆x
☆
●ＡＡＥＨ
Ｆ Ｕ ︲・Ｔい√holeｉ ｅｃ
Ｉ ＷＩBod、Dilfor.oncc

alY.

ＡＡ ＨＦＵ眈ＴＦara●一 〇\{rrsclea●Ａ Ａ Ｅ Ｈ
Ｆ Ｕ Ｌ ＴＢ●

●ElbOヽ ヽFll→'tio*、aKncca
Ｆ Ｆ

PlanierDorsal:__ial)izlgol i,

a1\\inl)! OhtsLrl(i 0 976)
(r 9i2)L.v KomiFiguro 4 Intra-pair differencts in monozygotic trvins.

23

The maximum isometric slrengths of flexors and extensors at elbow, knee and ankle joints
were indi 2. Strength irr the present study (measured strengthl *'ere obtained at the rvrist for elbow
joint, at the ankle for knt'e, and at thc b:rll of foot for Planter flexiolr and lt the instep for dorsrl
flexion. In elbow and krree joints the strengths for flexion showed smaller values that for extension.
In ankle.joint, the strength for planter flexion indicated 4.8 times of that for dorsal flexion.
The intra'pair di{ferences (lD) in the cross'sectional areas of tissues and the isomettic streirgth
were shown in Fig. 4. Frt indiclted rhe highest values of ID among three tissues, and it rvas tenderl
to be larger in the upper arm than ir rhe {orearm, ancl higher in the than in t}re leg. [t) o[ the lnrnein the upper arm and the rhigJr rv:rs higher thrn ttrose {o forearm and leg. respectively. Muscle indicated almost the same vahres of 6 7o1, n the forearm, the upper arm and the leg, whereas in the thighitwas\.Sfi, which rvas closer to the ID in brxly height. ID in the isrmetric m'rximum strcngttt intlicated higher values in flexion (Planter flexion) than in extension (dorsrl {lexion) irt knce and anlile

joint, whereas at elbow joint the slrenglh was almost the slme in both f]exion arld extensioo.
DISCUSSION

In order to discuss the genetic or environmental factors from the intra-pair difference of tissue
composition in monozygotic twin, it is nessesrry to get the enough accuracy or reprodrrcebility of themethod for measuring the composition of tissues. The accuracy and reproducebility of ultrasonic me'
thod for measuring crost'sectional area of tissues in human limbs was reported previously. Ikai andFukunaga (1970) reported that the differences of tissue area were 3 6!zo lrctrveen ultrasonic methodand direct method by rvhich cadavars specimen (arm and leg) \r'as cut cross directly, and the reproducebility was about 3 89/ f<tt eacb lissue area. In 1982, Fukunaga and Tsunoda repordte that the crosssection of tissu* by ultrasonic method indicnted about 7f/ higher value those b1' roentogen CT stanning method. From these prelious studies it mev be consirlered that the ultrasonic method is rrseful formeasuring cross-sectional areal o[ tissue in human limlx.

In t he present study [D ol fat indicated lrigher valueof 19 37 ?i comparecl r o orher tissue comp()sition. Ohtsuki and Klissouras (1976) measured the cross-sectional area of tissues in ttpp,:r iLrm foro9/monozygotic twins and reported rhar ID rvls 6 for the rvhc,ie section and musjle, 17?i [tt antl T ?'o()htsu-for bone. ID of muscle Ior rhe upper:!rm in the present studl. indicated almost same lalues as'l'lrc hig'kis. Other tissues like fat and bone shou,d higher ID in the present study than in Ohtsukis.
hest value of ID obtsined for fat in the present study was good agreement with OhtsukiS result'
In order to clarity genetic factor, it is of nessecity to compare the differeces oI ID between mo'innozygotic and dizygotic twin. In the previoudy (Ohtsuki and Klissouras, 1976) lD of tissue areabone31.
Sfuforfatand32.0|jIor
dizygotic twin was 9, 8fu for the whole pafi' 7. 8% for muxle,(Fig. 4). Compating these dasa for monozygotic and dizygotic trvins it is consirlered that interindividual
variations in bone can only ascril>ed to genetic differenceol 5 \5fu for isometric maximum strength in the presant study was good agreement o[ othelDprevious studies, which rvas 17.6% lor elbow flexors (Ohtsuki, 1976) md 73o/o for knee extensots(Komi, 1973).
REFERENCES

1. Fukunaga, 'f. Die absotute Muskelkraft und das lvluskelkrafttraining. Sportarzt und Sportmedizin 27 (r), 255265,1976.

24

2. Fukunaga, T and N. Tsunoda. Comparison hetween ultrasonic and CT method for measuring cross-s€ctional area
3.

of tissues in human. JSUM Proceedings 1982.
Ikai, M. and T. Fukunaga. Comparison henreen ultrasonic and direct methods to measuie the cross-sectional areaof tissue. Med. Ultrason. 8(1), 77-79, 1970.

4.

Inoue, E. Zysosity-diasnosis of Japanese twins by Essen-MollerS Iormula ( I ). In Fujita, T. (ed) ; Studies on

twins I[ (in japanese), Nihon Gakujutsu Shinkokai 1962.

5. Komi, P., V. Klissouras, and E. Karvinen. Genetic variation in neuromuscular rrerformance. Int. Z. Angeu. Physiol.,
31,289-304,1973.

6. Ohtsuki, T. and V. Klissouras Cenetic lxsis of individual differences in tissue coml)osition. Acta Genet. It{ed.
Camello) lRoma) 25, 157-163, 1976.