Department of Electrical and Electronical Engineering, Public University of Navarra, Pamplona, Spain.
Institute of Sport Sciences and Department of Physiology, University of Lausanne, Lausanne, Switzerland.
Scand J Med Sci Sports. 2017 Dec;27(12):1761-1775. doi: 10.1111/sms.12819. Epub 2016 Dec 28.
This study was designed to examine separately the changes in the first and second phases of the muscle compound action potential (M-wave) during and after a sustained 3-minutes maximal voluntary contraction (MVC). M-waves were evoked by supramaximal single shocks to the femoral nerve given at 10-seconds intervals throughout a sustained isometric 3-minutes MVC and also during six brief MVCs performed throughout a 30-minutes recovery period. The amplitude, duration, and area of the M-wave first and second phases, together with muscle conduction velocity and force, were measured. During the 3-minutes MVC, the amplitude of the first phase increased progressively for the first minute (33%-43%, P<.01) and remained stable thereafter, whereas the second phase initially increased for 25-35 seconds (30%-50%, P<.01), but subsequently decreased significantly before stabilizing. During the recovery period, the amplitude of the M-wave first phase showed a decreasing trend, returning to pre-fatigue values (P>.01) within 5-10 minutes, while the second phase increased progressively and remained higher than control (7%-20%, P<.01) after the 30-minutes recovery time. Maximal cross-correlations between the time course of the first phase amplitude and those of conduction velocity and force (0.9-0.93) occurred for a lag of 0 seconds, whereas maximal cross-correlations corresponding to the second-phase amplitude (0.6-0.7) occurred for a 50-seconds time lag. The present findings indicate that the potentiation of the first phase results from impaired muscle membrane excitability. The peak-to-peak amplitude and second-phase amplitude are not valid indicators of muscle excitability as they might be critically affected by muscle architectural features.
本研究旨在分别检测在持续 3 分钟最大自主收缩（MVC）期间和之后，肌肉复合动作电位（M 波）的第一和第二相的变化。通过在持续的 3 分钟等长 MVC 期间每隔 10 秒给予股神经最大单刺激，以及在 30 分钟恢复期内进行的 6 次短暂 MVC 期间，诱发 M 波。测量 M 波第一和第二相的幅度、持续时间和面积，以及肌肉传导速度和力。在 3 分钟 MVC 期间，第一相的幅度在前一分钟逐渐增加（33%-43%，P<.01），此后保持稳定，而第二相最初增加 25-35 秒（30%-50%，P<.01），但随后显著下降，然后稳定。在恢复期内，M 波第一相的幅度呈下降趋势，在 5-10 分钟内恢复到疲劳前值（P>.01），而第二相逐渐增加，并且在 30 分钟恢复时间后仍高于对照（7%-20%，P<.01）。第一相幅度的时间过程与传导速度和力的最大互相关（0.9-0.93）的滞后为 0 秒，而对应于第二相幅度的最大互相关（0.6-0.7）的滞后为 50 秒。本研究结果表明，第一相的增强是由于肌肉细胞膜兴奋性受损所致。峰峰值幅度和第二相幅度不是肌肉兴奋性的有效指标，因为它们可能受到肌肉结构特征的严重影响。
