Jakobsen, M. D., Sundstrup, E., Andersen, C. H., Zebis, M. K., & Andersen, L. L. (2011). Evaluation of neuromuscular fatigue indices during a full bout of resistance training. Medicine and Science in Sports and Exercise, 43(5). Supplement abstract 2300.

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This study evaluated levels of electromyographic (EMG) activity and fatigue indices during a standardized neck/shoulder resistance training bout in healthy sedentary women (N = 12). Maximal EMG activity and median power frequency of the trapezius (upper, mid, lower), deltoid muscle (anterior), infraspinatus, and serratus anterior were measured during three sets of 15 repetitions in four exercises (front raise, reverse flies, shrugs, and lateral raise) and normalized to EMG activity recorded during a maximal static contraction.

For most exercises and sets the level of maximal muscle activity was relatively high (>60% of maximal static contraction). Maximal EMG activity increased significantly and median power frequency decreased significantly from the first to last repetition within each set. There was little difference between sets.

Implication. During a full resistance training bout, indices of fatigue occur within each set but not between sets. One set produces the highest fatigue levels. The value of multiple exposures to the same resistance fatigue levels needs to be determined.

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