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幼少期の筋力トレーニングが成熟後のトレーニング効果に及ぼす影響について
東京大学大学院

山 田茂

The Influence of a Muscular Strength Training
in the Immature Period on Training Effect after Maturity

byShigeru Yamada
Graduate school of arts and sciences, Department of sports
sciences, The University of Tokyo

ABSTRACTThis study assessed the influence of muscle strength training in the immature period
on training effect after maturity. Seven- weeks-old male Wister rats were used in eachgroup（experimental and control group）． The tenotomy method was used to create amodel of muscle hypertrophy. The rats in the experimental group, were repeatedly
injected with bupivacaine to activate a satellite cells in their muscle tissue.
After three bupivacaine injections, the muscle weight of the bupivacaine
experimental group was recovered to the muscle weight of the control group, and atendon was then removed surgically. The muscle cells in the tissue of the control groupwere enlarged and exhibited muscle hypertrophy, and open spaces were observed in
the perimysium and endomysium. Small cells with central nuclei, were observed in theperimysium and endomysium.
Most muscle cells were newly generated after three bupivacaine injections. Most ofthe muscle fibers the contralateral muscle in the experimental group had central nuclei.
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In addition, enlarged cells formed by fusion between muscle cells were observed in
the muscle tissue in the tenotomy side in the experimental group.
The FGF was expressed in the muscles in the control group. and its expression
increased with compensation load. In the experimental group, on the other hand, thelevel of FGF gene expression on the contralateral side was extremely decrerased, but it
increased in response to a compensation load.
Increases in plantaris and soleus muscle weight after maturity were compared in thegroup in which muscle hypertrophy was induced by tenotomy in the immature period
and in the control group. The rates of increase in weight of the plantaris muscle, weresignificantly different between the two groups, and also there was a significant a socalled fast muscle, difference in the weight of soleus muscle, a so-called slow muscle,
between the two groups.
Muscle weight in the group of rats whose tendon was removed surgically in theimmature period increased in response to compensatory load. The results ofexperimental 1suggested that activation of satellite cells in the immature period
adversely affects muscle enlargement after maturity. However, no such results wereobtained in this experiment. Future study is needed to elucidate the case.の肥大と増殖によるものである．この筋細胞の肥はじめに大と増殖はサテライト細胞の活性化に依存する．

幼少期の筋力トレーニングが成熟後のトレーニ筋活動によりサテライト細胞が活性化され，増殖ング効果にどのような影響をおよぼすのであろう

し， その後，サテライト細胞は互いに融合してか？骨格筋の成長は個々の筋細胞の肥大と増殖に新たな筋線維を形成する 4)．さらに，既存の筋線よるものである．その筋細胞の増殖は成長ホルモ

維は肥大し，その筋線維には多くの核が含まれてン，テストステロンなどの内分泌系ホルモンの作いる．最終の分化産物である筋線維は細胞分裂や用によるものと，線維芽細胞成長因子，インスリ核分裂をしない．したがって肥大筋線維に含まれン様成長因子など自己分泌や傍分泌系の成長因子

る核の由来はサテライト細胞であることが示唆さ

1), 2), 3)．筋力トれる．このような視点で考えれば，サテライト細レーニングによる筋の成長にはこれら，内分泌系胞は，運動による筋肥大に欠くことのできない存

物質や成長因子に加え，機械的伸展刺激もその役在である．の働きによっておこるものがある割を担っている．In vitro での機械的伸展刺激に幼少期の筋力トレーニングは，発育にともなうよる実験研究から，筋そのものの活動が筋の成長サテライト細胞の活性化に加え，さらなる，サテを促すことが判明している．したがって筋活動にライト細胞の分裂を招くことが予想される．このよるトレーニング効果は幼少期から老年期まで期

ようにサテライト細胞は，骨格筋の補償細胞とし待される．て存在するものの，その分裂能には限界がある．

筋力トレーニングによる筋肥大も個々の筋細胞デサントスポーツ科学 Vol. 22

したがって，サテライト細胞の分裂を駆使するよ90

うな状態に何度もであった場合，その適応能力は徐々に失うものと考えられる．
そこで本実験では幼少期のトレーニングが成熟後のトレーニングに及ぼす影響について検討した．

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