title: Measurement of human skeletal muscle oxidative capacity by 31P-MR spectroscopy: a cross-validation with in vitro measurements.
abstract: OBJECTIVE
  To cross-validate skeletal muscle oxidative capacity measured by (31)P-MR spectroscopy with in vitro measurements of oxidative capacity in mitochondria isolated from muscle biopsies of the same muscle group in 18 healthy adults.
  
  
  METHODS
  Oxidative capacity in vivo was determined from PCr recovery kinetics following a 30-s maximal isometric knee extension. State 3 respiration was measured in isolated mitochondria using high-resolution respirometry. A second cohort of 10 individuals underwent two (31)P-MRS testing sessions to assess the test-retest reproducibility of the method.
  
  
  RESULTS
  Overall, the in vivo and in vitro methods were well-correlated (r = 0.66-0.72) and showed good agreement by Bland Altman plots. Excellent reproducibility was observed for the PCr recovery rate constant (CV = 4.6%; ICC = 0.85) and calculated oxidative capacity (CV = 3.4%; ICC = 0.83).
  
  
  CONCLUSIONS
  These results indicate that (31)P-MRS corresponds well with gold-standard in vitro measurements and is highly reproducible.
authors: Division of Endocrinology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
authors: Ian R
authors: IR
authors: Lanza
authors: Sumit
authors: S
authors: Bhagra
authors: K Sreekumaran
authors: KS
authors: Nair
authors: John D
authors: JD
authors: Port
mesh_terms: D000328:Adult; D001706:Biopsy / Q000379:methods; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007717:Knee / Q000473:pathology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D018482:Muscle, Skeletal / Q000473:pathology*; D009132:Muscles / Q000473:pathology; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010725:Phosphocreatine / Q000031:analogs & derivatives* / Q000378:metabolism; D010759:Phosphorus Isotopes / Q000494:pharmacology*; D015203:Reproducibility of Results
chemical_list: D010759:Phosphorus Isotopes; D010725:Phosphocreatine; C025403:phosphocreatinine; D010100:Oxygen