title: Effects of 84-days of bedrest and resistance training on single muscle fibre myosin heavy chain distribution in human vastus lateralis and soleus muscles.
abstract: OBJECTIVE
  This investigation determined the effects of 84 days of bedrest on the composition of myosin heavy chain (MHC) in single skeletal muscle fibres with and without a resistance-training countermeasure programme.
  
  
  METHODS
  Muscle biopsies were obtained from the m. vastus lateralis (VL) and m. soleus (SOL) before and after 84 days of bedrest. While control (BR) subjects (VL n = 9; SOL n = 3) refrained from exercise, BRE subjects (VL n = 8; SOL n = 3) performed knee extensor and plantar flexor resistance exercise every third day. Approximately 110 fibres per sample were analysed for MHC composition using SDS-PAGE.
  
  
  RESULTS
  BR-VL had 16 and 14% decreases (P < 0.05) in MHC I and IIa fibres, respectively. There were 10% increases (P < 0.05) in MHC I/IIa, IIa/IIx, I/IIa/IIx, and a approximately 30% increase (P < 0.05) in total hybrid fibres. BRE-VL showed a 15% reduction (P < 0.05) in MHC I fibres, no change in MHC IIa fibres, and a 13% increase (P < 0.05) in total hybrids. BR-SOL had a 19% decrease (P < 0.05) in MHC I fibres with a 22% increase in total hybrids. BRE-SOL showed no change in MHC composition across all fibre types.
  
  
  CONCLUSIONS
  These data suggest that the exercise countermeasures programme prevented MHC shifts in the SOL and mitigated MHC shifts in the VL. Furthermore, in the VL it appears that the resistance training programme employed in this investigation during bedrest, emphasized the use of MHC IIa phenotype muscle fibres.
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA.
authors.forename: P
authors.initials: P
authors.lastname: Gallagher
authors.forename: S
authors.initials: S
authors.lastname: Trappe
authors.forename: M
authors.initials: M
authors.lastname: Harber
authors.forename: A
authors.initials: A
authors.lastname: Creer
authors.forename: S
authors.initials: S
authors.lastname: Mazzetti
authors.forename: T
authors.initials: T
authors.lastname: Trappe
authors.forename: B
authors.initials: B
authors.lastname: Alkner
authors.forename: P
authors.initials: P
authors.lastname: Tesch
mesh_terms: D000328:Adult; D001510:Bed Rest; D004591:Electrophoresis, Polyacrylamide Gel; D015444:Exercise / Q000502:physiology*; D018475:Head-Down Tilt / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D018995:Myosin Heavy Chains / Q000378:metabolism*; D018474:Weightlessness Simulation
chemical_list: D018995:Myosin Heavy Chains