Froyd Christian, Beltrami Fernando G, Jensen Jørgen, Millet Guillaume Y, Noakes Timothy David
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, South Africa. ; Faculty of Teacher Education and Sport, Sogn og Fjordane University College, Norway.
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, South Africa.
J Hum Kinet. 2014 Oct 10;42:91-101. doi: 10.2478/hukin-2014-0064. eCollection 2014 Sep 29.
The aim of this study was to investigate the effect of potentiation on stimulation-induced muscle function during and after an intense bout of self-paced dynamic exercise. Ten active subjects performed a time trial involving repetitive concentric extension-flexion of the right knee using a Biodex dynamometer. Electrical stimulation before and after a 5 s maximal isometric voluntary contraction was performed before the start of the time trial and immediately (< 5 s) after each 20% of the time trial as well as 1, 2, 4 and 8 min after time trial termination. Potentiation was observed before the time trial and as early as 1-2 min after the time trial, but no potentiation was detected during or immediately after the time trial for neither single or paired stimuli. At termination of the time trial, "potentiated" peak torque was significantly more reduced than "unpotentiated" peak torque for single stimulus (-65 ± 10% and -42 ± 18%, respectively) and paired stimuli at 100 Hz (-51 ± 10% and -33 ± 15%, respectively). Faster recovery for "potentiated" compared to "unpotentiated" peak torque indicate that potentiate peak torque measurements or delay the post-exercise measurements more than a few seconds, will underestimate peripheral fatigue. In conclusion, the potentiation after maximal contraction disappears during intense exercise. Whether the muscle is already potentiated during intense contraction or fatiguing mechanisms inhibits potentiation remains to be clarified.
本研究的目的是调查在一场高强度的自定节奏动态运动期间及之后，增强作用对刺激诱发的肌肉功能的影响。十名活跃的受试者使用Biodex测力计进行了一项计时赛，内容为右膝重复的向心伸展-屈曲动作。在计时赛开始前以及在计时赛每完成20%之后立即（<5秒），以及在计时赛结束后1、2、4和8分钟，分别在5秒最大等长自主收缩之前和之后进行电刺激。在计时赛之前以及计时赛之后最早1-2分钟观察到了增强作用，但在计时赛期间或之后立即，无论是单刺激还是双刺激均未检测到增强作用。在计时赛结束时，单刺激（分别为-65±10%和-42±18%）和100赫兹双刺激（分别为-51±10%和-33±15%）的“增强的”峰值扭矩比“未增强的”峰值扭矩显著降低更多。与“未增强的”峰值扭矩相比，“增强的”峰值扭矩恢复更快，这表明增强的峰值扭矩测量或在运动后测量延迟超过几秒，将低估外周疲劳。总之，最大收缩后的增强作用在剧烈运动期间消失。肌肉在剧烈收缩期间是否已经处于增强状态，或者疲劳机制是否抑制增强作用，仍有待阐明。
