Concentric force enhancement during human movement
Concentric force enhancement during human movement
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DOI：
10.1046/j.1365-201x.2001.00915.x
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发表时间：
2001-12-01
期刊：
影响因子：
--
通讯作者：
Komi, PV
中科院分区：
文献类型：
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作者：
Finni, T;Ikegawa, S;Komi, PV
为了了解在体内缩短拉伸周期运动中增强同心性能的可能机制，本研究检查了最大和次最大人体运动中膝关节伸展扭矩、肌电图（EMG）活动和股外侧肌束长度。9名志愿者在预拉伸和预等距条件下完成最大同心膝关节伸展（120度s(-1)）。在膝关节角度为115度（180度=伸展）时，虽然缩短前的扭矩水平小于等距弯曲前（268比314 N m， P < 0.05），但预拉伸状态下的膝关节伸展扭矩更大（272比248 N m， P < 0.05）。在扭矩增强时刻，肌电活动水平和肌束长度在两种情况下没有差异。除了特定的实验条件外，这种增强可能与预拉伸条件下更长的束束长度（缩短4.1 cm, P < 0.05）以及长度-张力特性的改变有关。束长行为也被发现在单边，次最大的雪橇跳跃条件下发挥重要作用，其中预加载改变，但同心净脉冲和关节角运动是相同的。在预负荷较大的反复下降跳跃中，肌束长度的变化小于反运动跳跃，反运动跳跃的特点是在偏心阶段的力和活动水平较低。目前最大和次最大负荷条件的结果表明，拉伸-缩短周期肌肉功能的好处可能通过不同的相互作用机制来实现，这些机制可能是特定任务的。
In order to understand the possible mechanisms contributing to enhanced concentric performance in stretch-shortening cycle exercises in vivo the present study examined knee extension torque, electromyogram (EMG) activity and fascicle length of the vastus lateralis muscle in maximal and submaximal human movements. Maximal concentric knee extensions (120 degrees s(-1)) were done after pre-stretch and pre-isometric conditions by nine volunteers. During shortening at the knee angle of 115 degrees (180 degrees = extended) the knee extension torque was found to be greater in pre-stretch condition (272 vs. 248 N m, P < 0.05) although the torque level prior to shortening was smaller than in pre-isometric condition (268 vs. 314 N m, P < 0.05). At the moment of torque enhancement the EMG activity levels or fascicle lengths did not differ between the conditions. It is proposed that besides specific experimental conditions the present enhancement may be related to longer fascicle length prior to shortening (by 4.1 cm, P < 0.05) in pre-stretch condition and to modified length-tension properties. Fascicle length behaviour was found to play an important role also in unilateral, submaximal sledge-jump conditions where pre-loading was altered but the concentric net impulse and joint angular movements were the same. In repeated drop jumps with greater pre-load the changes in fascicle length were smaller than in the counter movement jump that was characterized by a lower force and activity level in the eccentric phase. Results from the present maximal and submaximal loading conditions suggest that the benefits of stretch-shortening cycle muscle function may come through different interactive mechanisms that may be task specific.