title: A noninvasive, log-transform method for fiber type discrimination using mechanomyography.
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.
authors.affiliation: Department of Health and Exercise Science, Biophysics Laboratory, University of Oklahoma, Norman, Oklahoma, USA.
authors.forename: Trent J
authors.initials: TJ
authors.lastname: Herda
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Housh
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Fry
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Weir
authors.forename: Brian K
authors.initials: BK
authors.lastname: Schilling
authors.forename: Eric D
authors.initials: ED
authors.lastname: Ryan
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
mesh_terms: D000465:Algorithms; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000145:classification* / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology* / Q000502:physiology*; D009213:Myography / Q000379:methods*; D055815:Young Adult