LIMB CONGESTION AND EXERCISE REFLEXES

Preliminary studies suggest that limb congestion may augment sympathetic nerve responses even more in the aged than in younger subjects. This is important since edema is a common clinical problem in the aged. In these studies, we will compare two study groups. We will contrast the effects of limb congestion sympathetic nerve responses to forearm exercises in a group of young and a group of old normal subjects. Each subject will perform two bouts of static handgrip exercise, with and without precongesting the forearm. We postulate that static exercise will evoke an increase in muscle sympathetic nerve activity (MSNA) in both subject groups. We further postulate that during a period of post-handgrip circulatory arrest (PHG-CA), sympathetic nerve traffic will remain elevated in both groups. In addition, we postulate that limb venous congestion will augment sympathetic nerve traffic in both groups during exercise but will have no effect on the MSNA response seen during PHG-CA. Based on our pilot data, we suspect that elderly individuals will have dramatic augmentation in MSNA in response to the venous congesting maneuver. Some subjects who do not have an increase in MSNA with exercise will have almost a 'normal' response after the forearm is congested.