Resting and Maximal Oxidative ATP Production Are Independent Parameters of Muscle Mitochondrial Function

Douglas E. Befroy¹, Ryan G. Larsen², Michael A. Tevald², Jane A. Kent-Braun²

Several MRS methods have been developed to investigate muscle mitochondrial function in-vivo. Although some studies have detected alterations in oxidative metabolism in the elderly and type-2 diabetes, others have discerned no effect. Resolving these disparities is confounded by differences in subject selection and muscle metabolic phenotype between studies, and by methodological differences between techniques. To establish whether correlated or independent parameters of mitochondrial metabolism are assessed by these methods, we have directly compared three ³¹P-MRS techniques: resting P_i → ATP flux, ischemic PCr decline and post-contraction PCr recovery, in a single muscle compartment in a group of healthy male subjects.