Department of Sport, Nutrition and Health Sciences, University of Milan, Milan, Italy.
J Electromyogr Kinesiol. 2012 Jun;22(3):348-55. doi: 10.1016/j.jelekin.2012.01.012. Epub 2012 Feb 20.
Peripheral fatigue and muscle cooling induce similar effects on sarcolemmal propagation properties. The aim of the study was to assess the combined effects of muscle temperature (Tm) manipulation and fatigue on skeletal muscle electrical and mechanical characteristics during isometric contraction. After maximum voluntary contraction (MVC) assessment, 16 participants performed brief and sustained isometric tasks of different intensities in low (Tm(L)), high (Tm(H)) and neutral (Tm(N)) temperature conditions, before and after a fatiguing exercise (6s on/4s off at 50% MVC, to the point of fatigue). During contraction, the surface electromyogram (EMG) and force were recorded from the biceps brachii muscle. The root mean square (RMS) and conduction velocity (CV) were calculated off-line. After the fatiguing exercise: (i) MVC decreased similarly in all Tm conditions (P<0.05), while EMG RMS did not change; and (ii) CV decreased to a further extent in Tm(L) compared to Tm(N) and Tm(H) in all brief and sustained contractions (P<0.05). The larger CV drop in Tm(L) after fatigue suggests that Tm(L) and fatigue have a combined and additional effect on sarcolemmal propagation properties. Despite these changes, force generating capacity was not affected by Tm manipulation. A compensatory mechanism has been proposed to explain this phenomenon.
周围性疲劳和肌肉冷却会对肌细胞膜传播特性产生相似的影响。本研究旨在评估肌肉温度（Tm）操作和疲劳对等长收缩期间骨骼肌电和机械特性的综合影响。在最大自主收缩（MVC）评估后，16 名参与者在低（Tm(L)）、高（Tm(H)）和中性（Tm(N)）温度条件下进行短暂和持续的等长任务，在疲劳运动（50% MVC 时 6 秒 ON/4 秒 OFF，直至疲劳）前后进行。在收缩过程中，从肱二头肌记录表面肌电图（EMG）和力。离线计算均方根（RMS）和传导速度（CV）。疲劳运动后：（i）所有 Tm 条件下的 MVC 均显著下降（P<0.05），而 EMG RMS 不变；（ii）在所有短暂和持续收缩中，Tm(L) 下的 CV 进一步下降，与 Tm(N)和 Tm(H)相比（P<0.05）。疲劳后 Tm(L) 下更大的 CV 下降表明 Tm(L)和疲劳对肌细胞膜传播特性具有综合和额外的影响。尽管发生了这些变化，但 Tm 操作并未影响产生力的能力。提出了一种补偿机制来解释这种现象。
