The acute effects of exercise and inactivity on vascular function
Poor endothelial function can predict future cardiac events. Exercise is effective in modifying cardiovascular risk by enhancing endothelial function, although the amount necessary to see benefits is not clear. The first aim was to examine the effects of acute exercise to alter endothelial function and nitric oxide metabolites in overweight and sedentary individuals.
Twenty-nine subjects were placed into 3 groups (Exercise, Inactive Control, Active Control). Sedentary and overweight subjects were assigned to the Exercise or Inactive Control Group, active normal weight individuals were assigned to the Active Control Group. The Exercise Group (N=15) came to the lab daily and had their resting blood flow, vascular resistance, conductance and peak reactive hyperemia measured in the calf. Measurements were made daily for 3 familiarization sessions and 24-hours following each of the 5 exercise sessions. The Exercise Group performed 60 minutes of cycling exercise for 5 days at 65% of their predicted maximal workload. Exercise was separated into 4 bouts of 15 minutes with 2 minutes of rest between each bout. Blood was drawn daily to determine if exercise altered plasma nitrate + nitrite concentration. These data were compared to the Inactive Control Group (N=5) who came to the lab for 6 consecutive days. The subjects in the Active Control Group (N=9) had 3 days of criterion measures to compare baseline differences with the Exercise Group.
At baseline the Active Group had significantly lower mean arterial pressure and greater peak reactive hyperemia and nitric oxide metabolites than the Exercise and Inactive Control Groups. There were no significant main effects for time (5 days of exercise) or group (Exercise vs. Inactive Control) and no interaction of group vs. time. Thus, 5 days of exercise is not sufficient to alter calf vascular function or nitric oxide metabolites in sedentary overweight individuals. The second aim of this dissertation was to examine how 5 days of rest following the cessation of exercise would alter calf reactive hyperemia and nitric oxide metabolites. Following the exercise protocol, subjects were inactive for 5 consecutive days. There were no significant changes in criterion measures on any of the rest days.