Affiliations: California State University, Fullerton, CA, USA
Correspondence:
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Corresponding author: Jared W. Coburn, Department of Kinesiology, Exercise Physiology Lab and Center for Sport Performance, 800 N. State College Blvd., KHS-235, California State University, Fullerton, Fullerton, CA 92834, USA. Tel.: +1 657 278 2629; Fax: +1 657 278 1548; E-mail:jcoburn@fullerton.edu
Abstract: OBJECTIVE: The study examined mechanomyographic (MMG) amplitude
(root mean square, RMS) and mean power frequency (MPF) vs. torque
relationships during isometric muscle actions in women with higher vs. lower
strength. METHODS: Eighteen women volunteered to perform isometric leg
extensions at 10 to 100% of their maximal voluntary contraction (MVC) on
an isokinetic dynamometer. The women were classified into lower strength (n = 10) and higher strength (n= 8) groups based on their isometric MVC values
(lower = 98.4 ± 18.3 Nm, higher = 162.8 ± 26.1 Nm). An
accelerometer was placed over the vastus lateralis to detect the MMG
amplitude (RMS) and frequency (MPF). Torque (Nm) was recorded by the
dynamometer. RESULTS: Polynomial regression analyses indicated the relationship
for normalized MMG amplitude vs. isometric MVC was quadratic for the lower
strength group (R2 = 0.989) and linear for the higher strength group
(R2 = 0.917). The MMG amplitude of lower strength women increased most
between 60 and 100% MVC. For MMG MPF, the relationships were linear for
both lower (R2 = 0.495) and higher strength women (R2 = 0.824). CONCLUSIONS: The different torque-related responses of MMG
amplitude for lower vs. higher strength women likely reflected differences
in absolute torque, and thus muscle stiffness, between groups.
Keywords: Isokinetic muscle actions, mechanomyography, motor control strategies, female
