"Alterations in muscle mitochondrial function have been implicated in the pathogenesis of numerous metabolic disorders, including insulin resistance, type 2 diabetes, obesity, and the deleterious effects of aging. However, the precise role for mitochondrial function in these processes remains to be established. In vivo 31P Magnetic Resonance Spectroscopy (31P-MRS) is an effective technique that permits the non-invasive investigation of skeletal muscle metabolism and transgenic mice are a novel tool for examining the effects of specific genes on mitochondrial function. Combining these two approaches would be a powerful methodology for studying mitochondrial function but its implementation has been limited due to the small volume of muscle from which the MR signal can be obtained and the requirement that the region of interest (ROI) must remain still for the entire duration of these lengthy studies. A new MR-compatible experimental set-up was developed to perform these experiments under low-dose anesthesia to minimize movement with constant physiological monitoring to ensure that the animal remains viable throughout the study. The unidirectional flux of ATP synthesis (Pi-->ATP) will be measured using 31P saturation-transfer MRS in differently modulated mouse models. In vivo MRS enables a unique outlook on skeletal muscle metabolism in situ. Its applications are limited not only to the study of mitochondrial function but may also be applied to other metabolic pathways."