Evaluation of recovery from local muscle fatigue by voluntary test contractions

The applicability of surface EMG frequency analysis as a means of evaluating recovery from local muscle fatigue was studied experimentally, fatigue being given as the proportion of the integrated value of frequency components below 60 Hz to that of all components. When the maximum voluntary contractions of elbow flexor were done repeatedly in the recovery period after dynamic or static contractions, the slow wave proportion recovered to the initial value within about 6 min after work. The muscle force of test contraction after 20 min or more was, however, still significantly lower than its initial value. Recovery of integrated EMG value was faster than that of muscle force but slower than that of slow wave components. The effect of blood flow occlusion on the recovery was then tested using different levels of load. When the occlusion was made for 4 min immediately following the sustained contractions, the slow wave component again increased after a phase of decrease but did not reach the final level attained at the end of work, implying that the observed changes in EMG frequency were somewhat related to local muscular fatigue of a peripheral nature. The recovery from local muscular fatigue may thus be evaluated by intermittent brief test contractions after muscular work.