静态负荷诱发肌肉疲劳后恢复期sEMG信号变化规律

目的:探讨肌肉疲劳过程中sEMG功率谱变化与H 的关系以及可能存在的其它影响因素.方法:利用肌肉进行疲劳收缩结束后,短时间内肌肉pH值尚无明显改变的特性,观察恢复期30 s内s EMG功率谱的变化规律.八名男性受试者,以肱二头肌为目标肌肉,负荷强度为60%MVC,静态持续负荷至疲劳点后,在恢复期以同样负荷分别观察2 s、4 s、6 s、8 s、10 s、20 s、30 s时的sEMG信号特征.结果:肱二头肌在以60%MVC静态疲劳负荷过程中MPF呈线性下降.在疲劳负荷后的恢复期,MPF恢复极其迅速,运动结束后仅2 s,MPF已恢复到整个下降范围的26.5%;至30 s,MPF已恢复到整个下降范围的87.7%.结论:由H ]增加引起的肌纤维动作电位传导速度下降不是决定sEMG功率谱左移的唯一因素,提示sEMG功率谱左移可能与神经源性的中枢机制的作用有关.

sEMG signal change characteristics during the short period of recovery after muscular fatigue with isometric contractions

Aim: To explore the factors affect the change of sEMG signal by investigating the relationship between power spectral changes of sEMG signal and H~ in muscle during the short period of recovery after muscular fatigue. Methods: After a fatiguing constriction of the muscle, its pH value would not be featured any apparent changes in a short period of time. However, we were able to observe the movement rule of the sEMG power spectrum within 30 s of its reversion duration. Surface EMGs of biceps brachii muscle were recorded from 8 healthy human volunteers during tasks. Muscle fatigue induced by isometric loading that included 60% of maximal voluntary contraction. Restitution of sEMG by recording 2 s, 4 s, 6 s, 8 s, 10 s, 20 s and 30 s by the same load after the end of the fatigue experiments of 60%MVC. Results: There was a significant monotonous decline in MPF during isometric fatigue contraction of 60% MVC. MPF was restituted rapidly in the short recovery period after muscular fatigue. It was recovered 26.5% of its whole declining scope only 2 s by the end of muscle movement, and has been reached 87.7% of its total decreasing value till 30 s after the exercise. Conclusion: Our results suggested that the accumulation of H~ in muscle was not the only factor that affected "spectrum shift" during muscle fatigue. The change of CNS drive strategy might be the important mechanisms that attributed to the change of SEMG signal during isometric contractions.