Change of Bio-electric Interferential Currents of Acute Fatigue and Recovery in Male Sprinters

Abstract

Detecting muscle fatigue and monitoring recovery from muscle fatigue are crucial in planning training and can help prevent overtraining and injuries. Surface electromyography (sEMG) is one of the most common non-invasive objective measures of muscle fatigue and recovery. However, the traditional measurements of sEMG are difficult to implement in out-of laboratory settings. Thus, an important issue in sports training is how to detect and predict muscle fatigue, and to monitor the recovery in an objective and easy-to-implement way. PURPOSE: To evaluate if bio-electric interferential currents (ICs), as applied by the Frequency Analysis Method (FAM), can be used to monitor the muscle fatigue and recovery of athletes. METHODS: In thirty male sprinters (aged 18-22 years), the following variables were obtained: the thresholds of ICs for sensory, motor and pain responses, the maximal voluntary contraction (MVC), and the amplitude of the surface EMG (aEMG). This was done prior to and immediately after an acute explosive fatigue training session, and during one-week recovery. Comparisons of different time points pre- and post-fatigue tests were analysed using ANOVA with repeated measures followed by Sidak for adjustment of multiple comparisons. Bland and Altman plot analysis was used to evaluate the agreement between the two measurements, IC thresholds and sEMG, on detecting fatigue and recovery. RESULTS: IC thresholds increased on average from 32.3 ± 8.9 mA to 37.5 ± 7.5 mA (p = 0.004) in sensory response at 10 Hz immediately post training but decreased at 24-hr (p = 0.008) post training and returned to pre-levels thereafter. Motor and pain response patterns were similar to the sensory response. The agreement between IC thresholds and aEMG/MVC ratio was good (> 95%). However, there was a time-shifted association between sensor responses at 10 Hz, 50 Hz and 100 Hz from pre- to immediately post-fatigue training and aEMG/MVC ratio from immediately post- to day 1 post-fatigue training. CONCLUSION: The present study suggested that the changes in IC thresholds were prior to the changes in both the aEMG and force during fatigue. FAM may be useful as an effective and simple tool for monitoring muscle fatigue during training and recovery in athletes. Supported by Shanghai University of Sport and Chengdu Sport University.