Departmental Bulletin Paper 高強度負荷運動に現れる酸素摂取量の緩慢相の機序

有光, 琢磨

125pp.111 - 156 , 2016-03-30 , 北海道大学大学院教育学研究院
高強度一定負荷運動時の酸素摂取量(VO2)は,遂行する仕事量に必要なエネルギー需要量以上に摂取される。これはVO2 slow componentと定義され検討されてきたが未だ不明である。現在,発生機構は,活動筋で説明されるが,活動筋内酸素消費や酸素供給のどちらに起因するか不明である。さらに,近年の研究は,疲労の影響も指摘される。本研究は,酸素供給や酸素利用の再検討,疲労の影響を明らからにする。その結果,運動時の全身への酸素供給はVO2動態と類似,活動筋への酸素供給の増大にも関わらずVO2 slow componentに影響が無い事を確認した。また,運動誘発性筋疲労は筋力の低下を引き起こしたが筋活動の変動は無く,筋力低下は中枢神経指令の低下でなく活動筋内収縮過程の阻害が影響している事が明らかとなった。以上より,活動筋内酸素利用が,VO2増大やVO2 slow componentを形成する事を示した。
Oxygen uptake(VO2) is additionally increased after the primary component until the end of exercise. This additional increase in VO2 is defined as the VO2 slow component, is still unclear. Recently, it has also been suggested that the VO2 slow component is derived from muscle fatigue. The purpose of this study was to re-determine the mechanism of VO2 slow component during heavy constant-load exercise. As a result, it was suggested that the VO2 slow component is not affected despite the oxygen supply to active muscle increase. In addition, exercise-induced muscle fatigue reduced the maximum voluntary contraction(MVC), although muscle electrical discharge in EMG did not fluctuate. It is revealed that the reduced MVC was not caused by the alteration of neurogenic activity but muscle contraction process after electric discharge. It is likely that muscle fatigue induces alteration of motor units and that fatigued motor units recovers a larger amount of oxygen consumption than do fresh motor units, resulting in appearance of the VO2 slow component. It is therefore concluded that the VO2 slow component is induced by oxygen utilization in active muscle, and muscle fatigue which changes the muscle contraction process after electric discharge.

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