Time course of changes in torque and neuromuscular parameters during a sustained isometric forearm flexion task to fatigue anchored to a constant rating of perceived exertion

Authors

Robert W. Smith, University of Nebraska-Lincoln
Terry J. Housh, University of Nebraska - LincolnFollow
John Paul V. Anders, University of Nebraska - Lincoln
Tyler J. Neltner, University of Nebraska - Lincoln
Jocelyn E. Arnett, University of Nebraska - Lincoln
Richard Schmidt, University of Nebraska - LincolnFollow
Glen O. Johnson, University of Nebraska – LincolnFollow

Document Type

Article

Date of this Version

5-8-2022

Citation

J Musculoskelet Neuronal Interact 2022; 22(4):455-464

Comments

Used by permission.

Abstract

Objective: This study examined the time course of changes in torque and electromyographic (EMG) and mechanomyographic (MMG) responses during a sustained isometric task anchored to a constant perception of exertion (RPE). Methods: Twelve college-aged men performed an isometric forearm flexion task to failure anchored to RPE=7 (OMNI-RES scale). The amplitude (AMP) and frequency (MPF) of the EMG and MMG signals from the biceps brachii were recorded. Repeated measures ANOVAs were used to examine differences for the normalized (%MVIC) torque and neuromuscular parameters. Results: The time to task failure (TTF) was 678.0±468.1s. Torque decreased significantly (p<0.001, η_p ²=0.774) across time and all subjects reduced torque to zero. Post-hoc comparisons indicated that the torque values from 20–100% TTF were less than the value at 10% TTF. There were no significant (p>0.05) changes from 10–100% TTF for the EMG and MMG parameters. Conclusion: We hypothesize that RPE was maintained by various mechanisms throughout the task: group III/IV afferent neurons, adequate blood flow, and a combination of reduced contractile efficiency, collective afferent feedback (group III/IV afferents) from muscles involved with forearm flexion, and motivation that resulted in an initial decrease, plateau, and final decline in torque to zero, respectively.