A Comparison of in Vivo and in Vitro Measurements of Skeletal Muscle Mitochondrial Capacity in Human Skeletal Muscle

Ian R. Lanza¹, K S. Nair², John D. Port³

Muscle oxidative capacity can be determined by 31P-MRS from phosphocreatine kinetics. We compared this approach two independent measurements of oxidative capacity performed using mitochondria isolated from skeletal muscle biopsy tissue in 11 volunteers. 31P-MRS was used to monitor the depletion and recovery of phosphocreatine following a 30 second maximal knee extension exercise. Oxidative capacity was also determined from measurements of maximal ATP production and respiration in mitochondria isolated from muscle biopsies. Oxidative capacity measured in vivo was significantly associated with maximal state 3 respiration and ATP production rates. 31P-MRS is a valid tool for assessment of mitochondrial oxidative capacity.