title: Myosin heavy chain isoform expression: influence on isoinertial and isometric performance.
abstract: Thirty-six healthy men with varying degrees of physical training background performed maximal-effort isometric and isoinertial knee extensor actions, with relative loads equal to 40% and 70% of one-repetition maximum. Force, velocity, and power were derived from force and linear position transducers at 500 Hz. Biopsies were taken from the vastus lateralis and analyzed by SDS-PAGE for relative myosin heavy chain (MHC) content. Relative MHC IIx content was included in a regression model, and explained variance noted. Relative MHC I content was subsequently added to the regression model to determine what, if any, additional variance was explained beyond that of MHC IIx. Results indicated that no relationship (r = 0.0 to 0.1) exists between the relative expression of MHC isoforms from the vastus lateralis and isometric/isoinertial performance in a population with diverse training backgrounds. Lack of nervous system adaptations in the untrained subjects in the study possibly attenuates the significant relationship between MHC and in-vivo muscle performance previously established in trained populations.
authors.affiliation: Department of Health and Sport Sciences, The University of Memphis, Memphis, Tennessee 38152, USA. bschllng@mempnis.edu
authors.forename: Brian K
authors.initials: BK
authors.lastname: Schilling
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Fry
authors.forename: Lawrence W
authors.initials: LW
authors.lastname: Weiss
authors.forename: Loren Z F
authors.initials: LZ
authors.lastname: Chiu
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018995:Myosin Heavy Chains / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D052097:Quadriceps Muscle / Q000378:metabolism / Q000502:physiology*; D014891:Weight Lifting / Q000502:physiology
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains