NMR Spectroscopy is used to study the metabolic changes associated with exercise in the flexor muscle of the forearm of human volunteers. Both isometric and isotonic protocols have been developed, to be used in conjunction with a hand dynamometer. Changes in phosphocreatine (PCr) and inorganic phosphate (Pi) as well as intracellular pH are monitored during the exercise. Age-related differences in these parameters during exercise will a studied in subjects of the BLSA.