Repeated Incremental Workbouts Separated by 1 Hour Increase the Electromyographic Fatigue Threshold

Bremer, N, Peoples, G, Hasler, B, Litzenburg, R, Johnson, A, and Malek, MH. Repeated incremental workbouts separated by 1 hour increase the electromyographic fatigue threshold. J Strength Cond Res 35(5): 1397-1402, 2021-Studies examining the influence of priming, for continuous exercise, have mainly focused on improved exercise capacity related to oxygen uptake kinetics rather than on neuromuscular fatigue of the muscle. The purpose of this study, therefore, was to determine whether or not the electromyographic fatigue threshold (EMG(FT)) could be modulated by having subjects perform 2 incremental tests separated by 1 hour. We hypothesized that the EMG(FT) determined from the second incremental test would be higher than the EMG(FT) determined from the first incremental test. Nine healthy college-aged men (mean +/- SEM: age: 23.8 +/- 0.6 years; body mass: 79.5 +/- 3.3 kg; height: 1.78 +/- 0.02 m) were recruited from the university population. Each subject visited the laboratory on 1 occasion and performed 2 incremental single-leg knee-extensor ergometry to voluntary fatigue separated by 1 hour. The EMG(FT) was determined for each trial and statistically compared using paired-samples t-test. The results indicated significant mean differences between the EMG(FT) for the 2 trials (trial 1: 27 +/- 1 W vs. trial 2: 34 +/- 2 W; p = 0.001), whereas there were no significant mean differences for maximal power output (trial 1: 53 +/- 2 W vs. trial 2: 57 +/- 2; p = 0.09). These findings suggest that postactivation potentiation may, in part, explain the differences in EMG(FT) because the exercise mode used in the current study minimizes the cardiorespiratory responses to exercise.