title: Intramuscular determinants of the ability to recover work capacity above critical power.
abstract: OBJECTIVE
  The primary purpose of this investigation was to compare the recovery of the W' to the recovery of intramuscular substrates and metabolites using (31)P- and (1)H-magnetic resonance spectroscopy.
  
  
  METHODS
  Ten healthy recreationally trained subjects were tested to determine critical power (CP) and W' for single-leg-extensor exercise. They subsequently exercised in the bore of a 1.5-T MRI scanner at a supra-CP work rate. Following exhaustion, the subjects rested in place for 1, 2, 5 or 7 min, and then repeated the effort. The temporal course of W' recovery was estimated, which was then compared to the recovery of creatine phosphate [PCr], pH, carnosine content, and to the output of a novel derivation of the W' BAL model.
  
  
  RESULTS
  W' recovery closely correlated with the predictions of the novel model (r = 0.97, p = 0.03). [PCr] recovered faster [Formula: see text] than W' [Formula: see text] The W' available for the second exercise bout was directly correlated with the difference between [PCr] at the beginning of the work bout and [PCr] at exhaustion (r = 0.99, p = 0.005). Nonlinear regression revealed an inverse curvilinear relationship between carnosine concentration and the W' t 1/2 (r (2) = 0.55).
  
  
  CONCLUSIONS
  The kinetics of W' recovery in single-leg-extensor exercise is comparable to that observed in whole-body exercise, suggesting a conserved mechanism. The extent to which the recovery of the W' can be directly attributed to the recovery of [PCr] is unclear. The relationship of the W' to muscle carnosine content suggests novel future avenues of investigation.
authors.affiliation: School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, Devon, EX1 2LU, UK, philip.skiba@advocatehealth.com.
authors.forename: Philip Friere
authors.initials: PF
authors.lastname: Skiba
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fulford
authors.forename: David C
authors.initials: DC
authors.lastname: Clarke
authors.forename: Anni
authors.initials: A
authors.lastname: Vanhatalo
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D000328:Adult; D002336:Carnosine / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D010725:Phosphocreatine / Q000378:metabolism; D010807:Physical Endurance
chemical_list: D010725:Phosphocreatine; D002336:Carnosine