Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships

Abstract

This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 ± 3.5 yrs) and 8 women (mean 21.0 ± 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R 2 = 0.983), where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r 2 = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric torque relationship in both the men (r 2 = 0.813) and women (r 2 = 0.578). The results demonstrated gender differences in the MMG amplitude vs. isometric torque relationship, but similar torque-related patterns for MMG mean power frequency. These findings suggested that the plateau in MMG amplitude at high levels of isometric torque production for the biceps brachii in the men, but not the women, may have been due to greater isometric torque, muscle stiffness, and/or intramuscular fluid pressure in the men, rather than to differences in motor unit activation strategies for modulating isometric torque production.

Time and frequency domain responses of the mechanomyogram and electromyogram during isometric ramp contractions: A comparison of the short-time Fourier and continuous wavelet transforms

“…These studies have reported that the MMG amplitude patterns of response: (a) increases linearly to MVC Shinohara et al, 1998;Zwarts and Keidel, 1991), (b) increases curvilinearly to MVC (Maton et al, 1990;Stokes and Cooper, 1992), (c) increases in an S-shaped pattern to MVC (Lammert et al, 1976), or (d) increases to 50-80% MVC (Beck et al, 2005cCoburn et al, 2005Ebersole et al, 1998Ebersole et al, , 1999Matheson et al, 1997; and then plateaus or decreases at higher torque levels. The minor variations among these responses may be related to factors that influence the MMG amplitude vs. isometric torque relationship during step contractions.…”

“…Other studies have examined the MMG amplitude vs. isometric torque relationship during incremental step contractions in the BB (Beck et al, 2005cEsposito et al, 1996;Maton et al, 1990;Zwarts and Keidel, 1991), superficial quadriceps femoris muscles (Coburn et al, 2005;Ebersole et al, 1998;Ebersole et al, 1999;Matheson et al, 1997;Shinohara et al, 1998;, and muscles of the hand (Stokes and Cooper, 1992). These studies have reported that the MMG amplitude patterns of response: (a) increases linearly to MVC Shinohara et al, 1998;Zwarts and Keidel, 1991), (b) increases curvilinearly to MVC (Maton et al, 1990;Stokes and Cooper, 1992), (c) increases in an S-shaped pattern to MVC (Lammert et al, 1976), or (d) increases to 50-80% MVC (Beck et al, 2005cCoburn et al, 2005Ebersole et al, 1998Ebersole et al, , 1999Matheson et al, 1997; and then plateaus or decreases at higher torque levels.…”

“…The minor variations among these responses may be related to factors that influence the MMG amplitude vs. isometric torque relationship during step contractions. These factors include the time windows chosen for signal analysis, the possibility of fatigue during sustained isometric contractions, muscle fiber type characteristics, the joint angle at which the muscle action is performed, and gender-related differences in motor control strategies (Akataki et al, 2003;Beck et al, 2005c;Ebersole et al, 1998Ebersole et al, , 1999Maton et al, 1990;Orizio, 1993). Overall, however the MMG amplitude patterns of response have been examined during isometric step contractions for the BB, superficial quadriceps femoris muscles, and two hand muscles, but these patterns have only been examined during isometric ramp contractions for the BB and FDI muscles.…”

“…Most of these investigations have performed isometric ''step'' contractions (Beck et al, 2005cBilodeau et al, 1991;Coburn et al, 2005Dalton and Stokes, 1993;Ebersole et al, 1998Ebersole et al, , 1999Lariviere et al, 2001;Maton et al, 1990), which involve separate isometric contractions performed at specific force increments from submaximal to maximal levels of force production (i.e., 20%, 40%, 60%, 80%, 100% MVC, etc.). The same step contraction principle has also been applied to dynamic muscle actions Coburn et al, 2005;, which may employ different motor control strategies (Kossev and Christova, 1998).…”

Spectral properties of electromyographic and mechanomyographic signals during isometric ramp and step contractions in biceps brachii

“…MMG has been used to study the MU recruitment strategies on the mechanical aspects of the muscle contraction, and the time and frequency domain parameters of the MMG reflect MU recruitment and firing rates, respectively (Orizio et al, 2003;Beck et al, 2005bBeck et al, , 2007a. Specifically, increases in the firing rates of individual MUs may result in an increase in the global MU firing rate, thereby resulting in a higher frequency MMG signal (Akataki et al, 2003;Beck et al, 2007a), whereas EMG frequency parameters have been shown to be insensitive to firing rate variation (Solomonow et al, 1990b).…”