Inter- and Intra-Individual Differences in EMG and MMG during Maximal, Bilateral, Dynamic Leg Extensions.

John Paul V Anders,Cory M Smith,Joshua L Keller,Ethan C Hill,Glen O Johnson,Richard J Schmidt,Terry J Housh

doi:10.3390/sports7070175

Abstract

The purpose of this study was to compare the composite, inter-individual, and intra-individual differences in the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during fatiguing, maximal, bilateral, and isokinetic leg extension muscle actions. Thirteen recreationally active men (age = 21.7 ± 2.6 years; body mass = 79.8 ± 11.5 kg; height = 174.2 ± 12.7 cm) performed maximal, bilateral leg extensions at 180°·s−1 until the torque values dropped to 50% of peak torque for two consecutive repetitions. The EMG and MMG signals from the vastus lateralis (VL) muscles of both limbs were recorded. Four 2(Leg) × 19(time) repeated measures ANOVAs were conducted to examine mean differences for EMG AMP, EMG MPF, MMG AMP, and MMG MPF between limbs, and polynomial regression analyses were performed to identify the patterns of neuromuscular responses. The results indicated no significant differences between limbs for EMG AMP (p = 0.44), EMG MPF (p = 0.33), MMG AMP (p = 0.89), or MMG MPF (p = 0.52). Polynomial regression analyses demonstrated substantial inter-individual variability. Inferences made regarding the patterns of neuromuscular responses to fatiguing and bilateral muscle actions should be considered on a subject-by-subject basis.

Highlights

Neuromuscular parameters from invasive [1] and non-invasive [2,3] assessments of muscle function have been used in laboratory and clinical settings to examine factors relating to physical performance [4] and muscular diseases [5]
The results indicated that there were no differences between limbs for any of the mean neuromuscular (EMG AMP, EMG mean power frequency (MPF), MMG AMP, or MMG MPF) responses during the fatiguing, maximal, bilateral, or isokinetic leg extension muscle actions
Matkowski et al [49] reported no differences between limbs for normalized EMG AMP from the RF, vastus medialis (VM), and vastus lateralis (VL) during bilateral leg extension MVICs

Summary

Introduction

Neuromuscular parameters from invasive [1] and non-invasive [2,3] assessments of muscle function have been used in laboratory and clinical settings to examine factors relating to physical performance [4] and muscular diseases [5]. Neuromuscular parameters have been used in a clinical setting to assess the influences of cerebral palsy [11], myotonic dystrophy [12], and Parkinson’s disease [13] on muscle function and to improve the control of human prosthetics [14,15]. The amplitude and frequency content of the EMG signal reflect muscle activation [3] and action. The amplitude and frequency of the MMG signal can reflect motor unit recruitment [2] and the global motor unit firing rate [17] of the activated unfused motor units, respectively

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