The overall goal of the research program in this laboratory is to better understand neural control of the circulation. Specifically, we have focused on sympathetic adjustments to physical stress in humans and the mechanisms responsible for these adjustments. We make direct intraneural recordings of sympathetic nerve activity using microneurography. Physical stressors include exercise, heat, orthostasis and exercise training. Mechanisms that have been examined include: muscle reflexes, arterial and cardiopulmonary baroreflexes, central command, and the vestibular system. Recently, one of our main focus of investigation has been the role that the vestibular system has on cardiovascular and sympathetic regulation. We have demonstrated otolith organ stimulation via head-down neck flexion increases muscle sympathetic nerve activity. However, increased sympathetic outflow activated by the otolith organs is not uniform to all vascular beds because sympathetic nerve activity to skin is not changed. Current studies are investigating how aging and simulated microgravity (i.e., bed rest) alter vestibular