The importance of pulsatile pressure and flow is manifested by impedance measurements, rate sensitivity of vascular beds and theoretical consideration of pulsatile pressure-flow dynamics. The proposed program will study the response of the skeletal muscle to pulse pressure waves of known characteristics (amplitude, dp/dt, frequency and mean values). A perfusion system which includes a pulse wave generator will be used to perfuse isolated gracilis muscle of dogs. The experiments on the isolated muscle will separate the local direct mechanical effects of pulsatile pressure and flow from the effects of central neurogenic control and variable blood constituents. The response to pulse pressures applied locally to the muscle will be compared with the response to pulse pressure applied to the thoracic aorta. Pulse pressure applied to the thoracic aorta will produce responses that include reflexes (baroreceptors) and hormonal changes (i.e. epinephrine) as well as local mechanical influences. Data analysis (computer) will utilize amplitide, dp/dt, frequency, mean values, total resistance impedance, capillary filtration coefficients (CFC), pre and post capillary resistance and oxygen utilization. Fourier analysis will be used when it is applicable.