9306596 Conley The experiments outlined in this proposal are to look at the mechanisms of maintaining muscle energy balance and sustained performance. Muscle contraction is dependent upon energy supply which in turn is dependent upon a number of metabolic and physiological processes. In this proposal the investigators will use magnetic resonance spectroscopy to determine the contractile demand and oxidative potential of the rattlesnake tail- shaker muscle during continuous contractions. The tail shaker muscles are sustaining high frequencing for over 30 minutes continuously and thus have high oxidative capacity to supply ATP for these contractions. The investigators will use a range of body temperature from 5 - 35 o C for rattling to look for demand under maximal conditions. In vivo muscle energetics will be determined using a test which involves 31P magnetic resonance spectroscopy to measure ATP breakdown and recovery changes in phosphocreatine content during muscle activation. The hypothesis is that energy flux during rattling changes as a simple temperature effect on the underlying rates of demand supply. This a model system for non-invasive evaluation of rate processes and the coordination of metabolism in vivo. ***
