Purpose: The purpose of this study was to utilize the Ratings of Perceived Exertion (RPE) Clamp Model to examine the effects of joint angle on the composite, inter-, and intra-individual patterns of responses for torque and neuromuscular parameters during fatiguing isometric tasks anchored to RPE of 8 (RPE = 8) at elbow joint angles of 75° (JA75) and 125° (JA125) for men. Methods: Ten men (Mean ± SD: age: 20.7 ± 1.2 yrs; height: 181.6 ± 6.0 cm; body mass: 83.7 ± 14.9 kg) performed 2,3 s forearm flexion maximal voluntary isometric contractions (MVIC) with the dominant arm before and after fatiguing isometric forearm flexion tasks anchored to RPE = 8, until task failure (defined as torque reduced to zero or RPE > 8), at JA75 and JA125. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii. Polynomial regression analyses (linear and quadratic) were performed to examine the patterns of responses for torque, EMG amplitude (AMP), EMG mean power frequency (MPF), MMG AMP, MMG MPF, and neuromuscular efficiency (NME). Six, separate 2 (Joint Angle: 75° vs 125°) x 2 (Time: Initial vs 5% Time to Task Failure [TTF]) repeated measures ANOVAs were used to assess the mean differences for torque and the neuromuscular parameters between the initial value and the value at 5%TTF. Results: There were significant (p ≤ 0.05) decreases in torque, EMG MPF, and NME from the initial value to 5%TTF that were not dependent on joint angle. At JA75 and JA125, there were significant (p ≤ 0.05) linear decreases in the composite patterns of responses for torque, EMG AMP, EMG MPF, and NME, but no significant (p > 0.05) changes across time for MMG MPF. For MMG AMP, there was a significant (p ≤ 0.05) linear decrease at JA125, but no significant (p ≥ 0.05) change at JA75. The individual patterns of responses for the neuromuscular parameters indicated substantial inter- and intra-individual variability that was affected by joint angle. Conclusion: The composite patterns of responses suggested that peripheral fatigue influenced the conscious decision to reduce torque to maintain RPE = 8. In addition, the individual patterns of responses indicated that various motor unit activation strategies, which may be joint angle-specific, are used when anchoring to a perceptual intensity.



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