Application of the Ratings of Perceived Exertion-Clamp Model to Examine the Effects of Joint Angle on the Time Course of Torque and Neuromuscular Responses During a Sustained, Isometric Forearm Flexion to Task Failure

Abstract

Application of the ratings of perceived exertion-clamp model to examine the effects of joint angle on the time course of torque and neuromuscular responses during a sustained, isometric forearm flexion to task failure. J Strength Cond Res 37(5): 1023-1033, 2023-The present study used the ratings of perceived exertion (RPE)-clamp model during a sustained, isometric forearm flexion task to failure to determine the effects of joint angle on torque and neuromuscular responses. Twelve college-aged women performed two 3-second maximal voluntary isometric contractions at elbow joint angles (EJ) of 75˚, 100˚, and 125˚before sustained, isometric, forearm flexions anchored to RPE 5 7 to task failure (defined as RPE . 7, or the torque was reduced to zero) at EJ 75 , EJ 100 , and EJ 125 . The amplitude (AMP) and frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals from the biceps brachii were recorded. Repeated-measures ANOVAs and post hoc comparisons were used to examine differences across time and between joint angles for torque and neuromuscular parameters. A p-value #0.05 was considered significant. For each joint angle, there was a decrease (p , 0.05) in torque across the sustained, isometric task. Collapsed across joint angle, there were decreases (p , 0.001, h 2 p 5 0.378) in EMG AMP from 30 to 100% time to task failure. No changes were observed, however, for the other neuromuscular responses. The subjects voluntarily reduced torque to maintain RPE 5 7 for each joint angle, and we hypothesize that RPE was maintained by afferent feedback from group III/IV motor neurons and corollary discharge (efferent copy of an internal signal that develops from central motor commands). The RPE-Clamp Model may be extended to athletes recovering from injury because a self-selected exercise intensity may be perceived as more enjoyable and promote adherence.

The Effects of Anchoring a Fatiguing Forearm Flexion Task to a High vs. Low Rating of Perceived Exertion on Torque and Neuromuscular Responses

“…In theory, differences in engaged muscle mass and torque production could result in differences in muscle oxygenation, adenosine triphosphate utilization, and metabolite buildup during the sustained isometric tasks (13). In addition, it has been hypothesized that fatigue-related differences in TTF between unilateral and bilateral tasks may be due to interhemispheric inhibition (1,18,36). Thus, these findings, in conjunction with those of Keller et al (18,19), suggested that the magnitude of performance fatigability following fatiguing isometric tasks anchored to RPE was dependent on the exercise mode and muscle group being examined.…”

“…Recent studies have examined the effects of joint angle (3), anchor scheme, and sex (36) on the torque and neuromuscular responses following fatiguing forearm flexion tasks anchored to RPE. Specifically, Arnett et al (3) examined the effects of joint angle on the MVIC and neuromuscular responses following fatiguing forearm flexion tasks anchored to RPE 5 8 in men and reported parallel decreases in pretest to posttest MVICs at elbow joint angles of 75°, 100°, and 125°, a decrease in EMG AMP at the elbow joint angle of 125°, and no changes in EMG MPF.…”

“…Therefore, the purpose of this study was to examine the torque and neuromuscular responses following sustained, isometric, forearm flexion tasks anchored to RPE 5 2 and RPE 5 8 (OMNI-RES scale). Based on the previous studies (3,36), it was hypothesized that (a) RPE…”

“…There was, however, an inverse relationship between exercise intensity and TTF (18). Thus, although the effects of joint angle (3), anchor scheme, and sex (36) have been assessed, it remains unclear whether there are differences in the torque and neuromuscular responses when fatiguing forearm flexion tasks are anchored to various RPE values. Therefore, the purpose of this study was to examine the torque and neuromuscular responses following sustained, isometric, forearm flexion tasks anchored to RPE 5 2 and RPE 5 8 (OMNI-RES scale).…”

The Effects of Anchor Schemes on Performance Fatigability, Neuromuscular Responses and the Perceived Sensations That Contributed to Task Termination

“…It has been suggested [14,15] that EMG AMP represents muscle excitation attributed to motor unit recruitment, firing rate, and/or synchronization. For example, previous studies have utilized EMG AMP to make inferences regarding fatigue-induced adjustments in motor unit activation strategies during and after sustained, isometric forearm flexion [7][8][9][10] and leg extension [11,16,17] tasks, with torque or force anchored to a constant RPE using the OMNI-RES (0-10) scale [18][19][20]. In addition, previous studies [21][22][23] have examined the ratio between normalized torque (or force) and normalized EMG AMP to estimate neuromuscular efficiency (NME: a measure of the level of excitation required to generate a given amount of torque).…”