Repeatability of surface EMG-based single parameter muscle fatigue assessment strategies in static and cyclic contractions

The repeatability of a spectral surface electromyography-based fatigue assessment strategy was evaluated. Variability of two fatigue-trend tracking parameters was used as an indicator for repeatability. The parameters were the natural logarithm of the slope of linear mean frequency decline lnMF_S and the percent drop in mean frequency MF_D. The coefficient of variation CoV was used as the metric for repeatability, representing the ratio of the standard deviation to the mean of repeated measures from the same individual. Five weekly fatigue tests on the right biceps brachii were conducted on 11 participants with a fatiguing regime comprising of alternating static and cyclic segments, collecting seven channels of differential EMG. The resulting 95% confidence intervals of the CoV were: 15.38-24.87% (Static lnMF_S), 12.21-23.36% (Cyclic lnMF_S), 13.18-21.85% (Static MF_D), and 12.37-24.39% (Cyclic MF_D). There was no statistically significant difference in repeatability between any combination of parameter and types of motion.