title: A decade of aerobic endurance training: histological evidence for fibre type transformation.
abstract: BACKGROUND
  Researchers employing a variety of training methods have demonstrated a fast-to-slow fibre transformation in animal skeletal muscle. The observation as to whether this occurs in exercise trained humans is limited and equivocal.
  
  
  METHODS
  
  
  
  METHODS
  to examine this issue, skeletal muscle from seven subjects who had participated in a decade or more of high intensity aerobic training (DT) and six nontrained (NT) subjects was obtained by muscle biopsy from the vastus lateralis muscle (VL) and subjected to a modified myofibrillar ATPase technique to identify muscle fibre types. Muscle tissue was histochemically treated by exposure to an alkaline preincubation (pH 9.9), an acid preincubation (pH 4.3 or 4.6) and the formate-KCI preincubation buffer (pH 4.54), previously employed in animal studies.
  
  
  RESULTS
  The formate-KCl preincubation medium identified all major fibre types at a single pH in human subjects. The percentage of type I fibres in DT was 70.9% vs 37.7% in NT (p<0.01), while the type IIa fibres in DT (25.3%) was much lower (p<0.01) than NT (51.8%). Surprisingly, type IIa fibres in the DT group displayed lesser oxidative staining intensity (p<0.01) than type IIa fibres from the NT group. Mean cross-sectional area of type I fibres for DT (6233.9+/-1421.7 microm2) was greater (p<0.05) than either type I (5746.8+/-1135.2 microm2) or II (5693.5+/-1214.6 microm2) from NT.
  
  
  CONCLUSIONS
  The results revealed that endurance training may promote a transition from type II to type I muscle fibre types and occurs at the expense of the type II fibre population.
authors: Department of Biology, Lakehead University Thunder Bay, Ontario, Canada. Robert.Thayer@Lakeheadu.ca
authors: R
authors: R
authors: Thayer
authors: J
authors: J
authors: Collins
authors: E G
authors: EG
authors: Noble
authors: A W
authors: AW
authors: Taylor
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch; D018657:Muscle Fibers, Slow-Twitch; D018482:Muscle, Skeletal / Q000166:cytology*; D010807:Physical Endurance / Q000502:physiology*
chemical_list: D000251:Adenosine Triphosphatases