A noninvasive, log-transform method for fiber type discrimination using mechanomyography
Received 31 August 2009; received in revised form 19 January 2010; accepted 19 January 2010. published online 22 February 2010. Corrected Proof
Abstract
This study examined the log-transformed mechanomyographic (MMGRMS) and electromyographic (EMGRMS) 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 EMGRMS and MMGRMS 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 MMGRMS and EMGRMS vs. force relationships, whereas the b coefficients were lower for the AT group than the RT and SED groups only in the MMGRMS vs. force relationship. The group differences among the a coefficients may have reflected subcutaneous fat acting as a filter thereby reducing EMGRMS and MMGRMS. The lower b coefficients for the AT group in the MMGRMS patterns may have reflected fiber area-related differences in motor unit activation strategies.
aDepartment of Health and Exercise Science, Biophysics Laboratory, University of Oklahoma, Norman, Oklahoma, USA
bNutrition and Health Science, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
cDepartment of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas, USA
dProgram in Physical Therapy, Des Moines University – Osteopathic Medical Center, Des Moines, Iowa, USA
eDepartment of Health and Sport Sciences, Human Performance Laboratory, University of Memphis, Memphis, Tennessee, USA
fHealth and Human Performance, Oklahoma State University, Stillwater, 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.
ABSTRACT