Comparison of Inter- and Intra-Individual Neuromuscular Patterns of Responses During Moderate-Load Bilateral Leg Extension Exercise

Taylor Dinyer-Mcneely,Haley C Bergstrom,Pasquale J Succi,M Travis Byrd,Caleb C Voskuil

doi:10.53520/rdsp2021.10515

Abstract

Introduction: This study examined the electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) responses during bilateral, leg extension exercise performed to failure at a moderate (70% one-repetition maximum [1RM]) load. Methods: Eleven men completed a 1RM and repetitions to failure at 70% 1RM of the leg extension. The EMG and MMG signals were recorded from the right and left vastus lateralis. Polynomial regression analyses were used to determine individual and composite, normalized neuromuscular responses for both limbs. Results: For EMG AMP, both limbs demonstrated positive, quadratic relationships. For EMG MPF, the right limb demonstrated a negative, cubic relationship and the left limb demonstrated a negative, quadratic relationship. For MMG AMP, the right limb demonstrated a positive, quadratic relationship and the left limb demonstrated a positive, linear relationship. For MMG MPF, both limbs demonstrated negative, linear relationships. 18-45% of the subjects demonstrated the same responses as the composite for the EMG and MMG signals. 14% of the subjects demonstrated the same direction and pattern of response for the right and left limb intra-individual responses. Conclusions: The variability in the inter- and intra-individual responses highlight the necessity to report individual neuromuscular responses when examining fatiguing resistance exercise.

Highlights

This study examined the electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) responses during bilateral, leg extension exercise performed to failure at a moderate (70% one-repetition maximum [1RM]) load
The purpose of this study was to examine the inter- and intra-individual EMG AMP, EMG MPF, MMG AMP, and MMG MPF patterns of responses of the right and left limbs during dynamic constant external resistance (DCER), bilateral, leg extension exercise performed to failure at a moderate (70% onerepetition maximum [1RM]) load
2 of the 11 subjects demonstrated a positive, quadratic relationship (r2 = 0.564 – 0.793), consistent with that demonstrated for the composite, left limb EMG AMP response

Summary

Introduction

This study examined the electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) responses during bilateral, leg extension exercise performed to failure at a moderate (70% one-repetition maximum [1RM]) load. Electromyography (EMG) and mechanomyography (MMG) measure the electrical and mechanical components of muscle,[1,2] respectively, and can be used to examine the fatigue response during repetitive muscle actions Both have time (amplitude [AMP]) and frequency (mean power frequency [MPF]) domains that reflect different components of a muscle contraction.[1,2,3,4] For EMG, the AMP reflects muscle excitation and includes both motor unit recruitment and motor unit firing rate, and the MPF reflects the motor unit action potential conduction velocity traveling along the sarcolemma.[1,4] The MMG signal records the lateral oscillations of the muscle. Investigators have reported increases in EMG and MMG AMP and decreases in EMG and MMG MPF over time during fatiguing isokinetic, isometric, and dynamic constant external resistance (DCER) muscle actions.[5,6,7,8] These responses indicate there are increases in muscle excitation and motor unit recruitment and decreases in the motor unit action potential conduction velocity and the motor unit firing rate to maintain force production during the fatiguing task

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