Bosco C, Tihanyi J, Latteri F, Fekete G, Apor P, Rusko H
Acta Physiol Scand. 1986 Sep;128(1):109-17. doi: 10.1111/j.1748-1716.1986.tb07955.x.
Stretch-shortening exercises are characterized by enhancement of performance when compared to the work output performed in shortening conditions. There is evidence that fast subjects are unable to re-use great amounts of elastic energy during stretch-shortening cycles performed with slow stretching speed and large stretching length. In the present study, 14 subjects possessing different fibre types in m. vastus lateralis performed vertical jumps with and without preliminary countermovement and with large angular displacement and slow stretching speed The jumping tests were executed before and immediately after fatigue induced by short intense exercises (60 s of continuous rebound jumping). The results indicated that the percentage of re-use of elastic energy was more pronounced in slow subjects compared to fast ones during the test performed before fatigue (28.3% vs. 22.8%). In contrast fast subjects demonstrated a greater percentage re-use of elastic energy than slow ones after fatigue (32% vs. 22.5%). Similarly, the negative relationship observed before fatigue, between the percentage of re-use of elastic energy and percentage of fast twitch fibres (r = 0.50, n = 14, P less than 0.05), was reversed after fatigue (r = 0.55, n = 14, P less than 0.05). The results can be interpreted through differences in sarcomere cross-bridges life-times between fast and slow twitch muscle fibres. The slow twitch-type muscle fibre may be able to retain the cross-bridge attachment for a longer period of time during no fatigued conditions, and therefore it may utilize elastic energy better in slow type ballistic motion. On the other hand, fast twitch type muscle fibres are more affected by fatigue, which might have induced a remarkable decrease of the cross-bridge attachment detachment cycle. Decrease of the cross-bridge rate cycle might allow fast twitch-type muscle fibres to retain longer the elastic energy stored during the stretching phase and then re-use it during positive phase.
与在缩短状态下完成的功输出相比，拉长-缩短练习的特点是表现增强。有证据表明，在以缓慢拉伸速度和大拉伸长度进行的拉长-缩短循环中，快肌受试者无法重新利用大量弹性能量。在本研究中，14名股外侧肌具有不同纤维类型的受试者进行了垂直跳跃，有无预摆且角位移大、拉伸速度慢。跳跃测试在短时间高强度运动（60秒连续反弹跳跃）引起疲劳之前和之后立即进行。结果表明，在疲劳前进行的测试中，慢肌受试者弹性能量的重新利用率比快肌受试者更显著（28.3%对22.8%）。相反，疲劳后快肌受试者的弹性能量重新利用率比慢肌受试者更高（32%对22.5%）。同样，疲劳前观察到的弹性能量重新利用率百分比与快肌纤维百分比之间的负相关关系（r = 0.50，n = 14，P小于0.05）在疲劳后发生了逆转（r = 0.55，n = 14，P小于0.05）。这些结果可以通过快肌和慢肌纤维肌节横桥寿命的差异来解释。慢肌型肌纤维在无疲劳状态下可能能够将横桥附着保持更长时间，因此在慢型弹道运动中可能能更好地利用弹性能量。另一方面，快肌型肌纤维更容易受到疲劳影响，这可能导致横桥附着-脱离循环显著减少。横桥速率循环的减少可能使快肌型肌纤维在拉伸阶段储存的弹性能量保留更长时间，然后在正向阶段重新利用。
