title: Noninvasive monitoring of training induced muscle adaptation with 31P-MRS: fibre type shifts correlate with metabolic changes.
abstract: OBJECTIVE
  To evaluate training induced metabolic changes noninvasively with (31)P magnetic resonance spectroscopy ((31)P-MRS) for measuring muscle fibre type adaptation.
  
  
  METHODS
  Eleven volunteers underwent a 24-week training, consisting of speed-strength, endurance, and detraining (each 8 weeks). Prior to and following each training period, needle biopsies and (31)P-MRS of the resting gastrocnemius muscle were performed. Fibre type distribution was analyzed histologically and tested for correlation with the ratios of high energy phosphates ([PCr]/[P(i)], [PCr]/[βATP] and [PCr + P(i)]/[βATP]). The correlation between the changes of the (31)P-MRS parameters during training and the resulting changes in fibre composition were also analysed.
  
  
  RESULTS
  We observed an increased type-II-fibre proportion after speed-strength and detraining. After endurance training the percentage of fast-twitch fibres was reduced. The progression of the [PCr]/[P(i)]-ratio was similar to that of the fast-twitch fibres during the training. We found a correlation between the type-II-fibre proportion and [PCr]/[P(i)] (r = 0.70, P < 0.01) or [PCr]/[βATP] (r = 0.69, P < 0.01); the correlations between its changes (delta) and the fibre-shift were significant as well (delta[PCr]/[P(i)] r = 0.66, delta[PCr]/[βATP] r = 0.55, P < 0.01).
  
  
  CONCLUSIONS
  Shifts in fibre type composition and high energy phosphate metabolite content covary in human gastrocnemius muscle. Therefore (31)P-MRS might be a feasible method for noninvasive monitoring of exercise-induced fibre type transformation.
authors.affiliation: Clinic for Orthopaedics, Center for Musculoskeletal Surgery and Julius Wolff Institute, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany. eike.hoff@charite.de
authors.forename: Eike
authors.initials: E
authors.lastname: Hoff
authors.forename: Lars
authors.initials: L
authors.lastname: Brechtel
authors.forename: Patrick
authors.initials: P
authors.lastname: Strube
authors.forename: Paul
authors.initials: P
authors.lastname: Konstanczak
authors.forename: Gisela
authors.initials: G
authors.lastname: Stoltenburg-Didinger
authors.forename: Carsten
authors.initials: C
authors.lastname: Perka
authors.forename: Michael
authors.initials: M
authors.lastname: Putzier
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D064797:Physical Conditioning, Human / Q000379:methods*; D010809:Physical Fitness / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D010710:Phosphates