Velocity-Specific Coactivation and Neuromuscular Responses to Fatiguing, Reciprocal, Isokinetic, Forearm Flexion, and Extension Muscle Actions.

Abstract

Abstract Neltner, TJ, Anders, JPV, Keller, JL, Smith, RW, Housh, TJ, Schmidt, RJ, and Johnson, GO. Velocity-specific coactivation and neuromuscular responses to fatiguing, reciprocal, isokinetic, forearm flexion, and extension muscle actions. J Strength Cond Res 36(3): 649–660, 2022—The purpose of this study was to examine the effects of fatiguing, reciprocal, maximal, isokinetic, forearm flexion, and extension on coactivation. Ten recreationally trained women (mean ± SD: age = 21 ± 1.63 years) performed 50 maximal, reciprocal, isokinetic, forearm flexion, and extension muscle actions at 60 and 180°·s−1 on separate days. Electromyographic (EMG) and mechanomyographic (MMG) signals from the biceps brachii (BB) and triceps brachii (TB) were recorded. A 2 (time) × 2 (velocity) × 2 (movement) and 4 separate 2 (time) × 2 (velocity) × 2 (muscle) × 2 (movement) repeated-measures analysis of variances were used to examine normalized torque and normalized EMG and MMG amplitude (AMP) and mean power frequency, respectively, with an alpha of p < 0.05. There were no significant interactions for torque but a main effect for time (p < 0.001, d = 3.29) such that it decreased. There was a significant four-way interaction for EMG AMP (p = 0.004, = 0.61) which revealed parallel responses between the BB and TB during both movements, with no changes at 60°·s−1 and increases at 180°·s−1. The current findings suggested a common drive between agonist and antagonist muscles during fatiguing forearm flexion and extension muscle actions, with velocity-specific activation strategies. In addition, both EMG and MMG are viable techniques for assessing coactivation during fatiguing exercise.