title: Noninvasive estimation of myosin heavy chain composition in human skeletal muscle.
abstract: OBJECTIVE
  Information on muscle fiber type composition is of great importance in muscle physiology and athletic performance. Because there are only a few techniques available that noninvasively and accurately provide an estimate of muscle fiber type composition, the development of additional and alternative approaches is required.
  
  
  METHODS
  Twenty-seven participants (21 men, 6 women) with an average age of 43 ± 18 yr, height of 175 ± 7 cm, and mass of 74 ± 12 kg participated in the study. Delay, contraction, and half relaxation times were calculated from tensiomyographic radial twitch responses of the vastus lateralis muscle. Univariate and multiple linear regression analyses were used to correlate the proportion of myosin heavy chain I (%MHC-I) in a biopsy obtained from the same muscle with a single and all three radial twitch parameters.
  
  
  RESULTS
  Delay, contraction, and half relaxation times all correlated with %MHC-I (r = 0.612, 0.878, and 0.669, respectively, at P ≤ 0.001). When all three parameters were included in a multiple linear regression, the correlation with the %MHC-I was even better (R = 0.933, P < 0.001).
  
  
  CONCLUSIONS
  These data suggest that time parameters of the skeletal muscle mechanical radial twitch response, measured with a contact linear displacement sensor, can be used as an accurate noninvasive predictor of the %MHC-I in a muscle.
authors.affiliation: Institute for Kinesiology Research, Science and Research Centre Koper, University of Primorska, Koper, Slovenia. Bostjan.simunic@zrs.upr.si
authors.forename: Boštjan
authors.initials: B
authors.lastname: Simunič
authors.forename: Hans
authors.initials: H
authors.lastname: Degens
authors.forename: Jörn
authors.initials: J
authors.lastname: Rittweger
authors.forename: Marco
authors.initials: M
authors.lastname: Narici
authors.forename: Igor B
authors.initials: IB
authors.lastname: Mekjavić
authors.forename: Rado
authors.initials: R
authors.lastname: Pišot
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000502:physiology; D018995:Myosin Heavy Chains / Q000032:analysis* / Q000502:physiology
chemical_list: D018995:Myosin Heavy Chains