Changes in Blood Flow, Temperature and Muscle Endurance in Association with Cryotherapy

[Purpose] Sustained isometric muscle actions induce fatigue which manifests as a decline in force. This decline has well known physiological correlates that are often assessed using EMG signal frequency changes, changes in blood flow and muscle temperature. The purpose of this study was to investigate how cooling influences recovery following isometric muscle fatigue. [Methods] Eight healthy volunteers performed isometric elbow flexion to fatigue on two occasions, with 10 minutes of rest with no cooling, 2 minutes and 10 minutes cooling. The surface EMG (median frequency), deep muscle temperature and circulating blood flow were assessed during and after each endurance task. [Results] The 10-minute cooling condition extended endurance in the isometric contraction task. No changes to median frequency EMG signals were detected and the deep temperature and blood flow was most profoundly affected with the extended period of cooling compared to rest and 2 minutes. [Conclusion] This exercise task was enough to induce fatigue in this study. It was shown that 10 minutes cooling for fatigued muscles will extend the duration of subsequent exercise. Indeed, the results of this study suggest the effects of muscle fatigue recovery by cooling are instantaneous.