Faculty of Sport Sciences, EA 2991 Motor Efficiency and Deficiency Laboratory, 700 Avenue du Pic Saint Loup, 34090 Montpellier, France.
Muscle Nerve. 2010 May;41(5):642-50. doi: 10.1002/mus.21512.
This study aimed to determine whether the time-course of maximal resting H-reflex amplitude (H(max)) recovery after a prolonged moderate-intensity muscle contraction differs according to the optimal stimulation intensity used (predetermined vs. readjusted). Thirteen males performed a sustained isometric plantar flexion at 40% of their maximal voluntary contraction torque output until exhaustion. H(max) of the soleus muscle was recorded before and 2, 6, 10, and 14 min after the end of the contraction, then normalized by the respective maximal M-wave to form the H(max)/M(max) ratio. During recovery, pre- and redetermined optimal stimulation intensities (mini-recruitment curve drawn before each recovery measurement) were applied randomly to measure H(max). When using redetermined stimulation intensities, normalized H-reflex values were systematically greater (+11, +16, +15, and +15% after 2-, 6-, 10-, and 14-min recovery periods, respectively) than those obtained with the predetermined intensity. Keeping the stimulation intensity constant to evoke H(max) after a sustained muscle contraction can underestimate the H-reflex facilitation occurring after exhaustive exercise. It is therefore more appropriate to redefine the optimal stimulation intensity to evoke H(max) (using mini-recruitment curves) when the purpose is to analyze spinal modulation during the recovery phase.
本研究旨在确定在长时间中等强度肌肉收缩后，最大静息 H 反射幅度（H(max)）恢复的时程是否因所使用的最佳刺激强度而异（预先确定的与重新调整的）。13 名男性以其最大自主收缩扭矩输出的 40%进行持续等长足底屈曲，直至力竭。在收缩结束后 2、6、10 和 14 分钟，分别记录比目鱼肌的 H(max)，然后通过各自的最大 M 波进行归一化，形成 H(max)/M(max) 比值。在恢复过程中，随机应用预先确定和重新确定的最佳刺激强度（在每次恢复测量前绘制的微型募集曲线）来测量 H(max)。当使用重新确定的刺激强度时，归一化的 H 反射值系统地更高（分别在 2、6、10 和 14 分钟的恢复期间增加了 11%、16%、15%和 15%），而不是使用预先确定的强度获得的值。在进行持续肌肉收缩后保持刺激强度不变以诱发 H(max)可能会低估力竭运动后发生的 H 反射易化。因此，当目的是在恢复阶段分析脊髓调制时，更适合重新定义诱发 H(max)的最佳刺激强度（使用微型募集曲线）。
