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Abstract

Purpose: The purpose of this study was to examine the effects of sustained, isometric forearm flexion tasks anchored to a rating of perceived exertion (RPE) versus torque on the composite, inter-, and intra-individual patterns of responses for torque and neuromuscular parameters, as well as the perceived factors that contributed to task termination. Methods: Ten men (mean ± SD: age = 20.9 ± 2.2 yrs.; height = 180.0 ± 5.1 cm; body mass = 81.3 ± 10.0 kg) performed maximal voluntary isometric contractions (MVICs) before and after sustained, isometric forearm flexion tasks anchored to RPE = 6 (RPE6FT) and the torque (TRQ6FT) that corresponded to RPE = 6, and completed post-test questionnaires (PTQs) with 10 Likert-type items immediately following the fatiguing tasks. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii during the fatiguing tasks. Polynomial regression analyses, dependent t-tests, Spearman’s rank order correlations, and Wilcoxon signed rank tests were used to analyze the data. Results: The RPE6FT had a greater (p < 0.001) TTF than the TRQ6FT, but there was no difference (p = 0.144) in performance fatigability. There was a significant (p < 0.001) composite linear decrease for torque during the RPE6FT, but no significant (p = 0.111) composite change for torque during the TRQ6FT. During the RPE6FT, there were significant (p ≤ 0.05) composite linear decreases in EMG amplitude (AMP), EMG mean power frequency (MPF), MMG MPF, and neuromuscular efficiency (NME = normalized torque / normalized EMG AMP), and a quadratic increase in MMG AMP. During the TRQ6FT, there was a significant (p ≤ 0.05) composite linear increase for EMG AMP, linear decreases for EMG MPF, MMG AMP, and NME, and a quadratic decrease for MMG MPF. There was substantial intra-individual variability for the torque responses and inter- and intra-individual variability for the neuromuscular responses. The PTQ item responses indicated greater (p = 0.003) BB fatigue for the TRQ6FT than the RPE6FT. There were no significant (p > 0.05) associations among the perceived factors and TTF or performance fatigability. Conclusion: There were anchor scheme-specific differences in TTF, composite torque and neuromuscular responses, and the perceived sensation of BB fatigue, but no differences for performance fatigability or the other 9 PTQ item responses. In addition, more than one of the PTQ items contributed to the decision to terminate the RPE6FT and TRQ6FT, but none of the 10 PTQ items were related to TTF or performance fatigability. Therefore, it is likely that other physiological and psychological factors contributed to task termination during the fatiguing tasks anchored to RPE and torque.

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