A noninvasive, log-transform method for fiber type discrimination using mechanomyography

Herda, Trent J.; Housh, Terry J.; Fry, Andrew C.; Weir, Joseph P.; Schilling, Brian K.; Ryan, Eric D.; Cramer, Joel T.

doi:10.1016/j.jelekin.2010.01.004

« Previous Next »Journal of Electromyography and Kinesiology
Volume 20, Issue 5 , Pages 787-794, October 2010

A noninvasive, log-transform method for fiber type discrimination using mechanomyography

Trent J. Herda
- Department of Health and Exercise Science, Biophysics Laboratory, University of Oklahoma, Norman, Oklahoma, USA
Terry J. Housh
- Nutrition and Health Science, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
Andrew C. Fry
- Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas, USA
Joseph P. Weir
- Program in Physical Therapy, Des Moines University – Osteopathic Medical Center, Des Moines, Iowa, USA
Brian K. Schilling
- Department of Health and Sport Sciences, Human Performance Laboratory, University of Memphis, Memphis, Tennessee, USA
Eric D. Ryan
- Health and Human Performance, Oklahoma State University, Stillwater, Oklahoma, USA
Joel T. Cramer
- Department of Health and Exercise Science, Biophysics Laboratory, University of Oklahoma, Norman, Oklahoma, USA
- Corresponding author. Address: Biophysics Laboratory, Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Rm 12, Norman, OK 73019-6081, USA. Tel.: +1 405 325 5211; fax: +1 405 325 0594.

Received 31 August 2009; received in revised form 19 January 2010; accepted 19 January 2010. published online 22 February 2010.

Abstract

This study examined the log-transformed mechanomyographic (MMG_RMS) and electromyographic (EMG_RMS) amplitude vs. force relationships for aerobically-trained (AT), resistance-trained (RT), and sedentary (SED) individuals. Subjects performed isometric ramp contractions from 5% to 90% maximal voluntary contraction. Muscle biopsies were collected and thigh skinfolds, MMG and EMG were recorded from the vastus lateralis muscle. Linear regression models were fit to the log-transformed EMG_RMS and MMG_RMS vs. force relationships. The slope (b coefficient) and the antilog of the y-intercept (a coefficient) were calculated. The AT group had the highest percentage of type I fiber area, the RT group had the highest percentage of type IIa fiber area, and the SED group had the highest percentage of type IIx fiber area. The a coefficients were higher for the AT group than the RT and SED groups in both the MMG_RMS and EMG_RMS vs. force relationships, whereas the b coefficients were lower for the AT group than the RT and SED groups only in the MMG_RMS vs. force relationship. The group differences among the a coefficients may have reflected subcutaneous fat acting as a filter thereby reducing EMG_RMS and MMG_RMS. The lower b coefficients for the AT group in the MMG_RMS patterns may have reflected fiber area-related differences in motor unit activation strategies.