Plasma norepinephrine responses to posture and isometric exercise increase with age in the absence of obesity.

This study examines the effects of age on plasma norepinephrine (NE) responses to upright posture and isometric handgrip exercise in nonobese men. Increasing age was associated with increased basal levels of plasma NE as well as increased NE responses to upright posture. These results suggest that aging affects sympathetic system activity by mechanisms largely independent of the increasing adiposity generally associated with aging.