B-26 Free Communication/Poster - Cardiorespiratory Fitness

Abstract

Introduction: Sitting time is associated with multiple cardiovascular and metabolic disease risk factors. Breaking sitting time has been reported to have beneficial associations with cardiovascular and metabolic risk. The direct effects breaking sitting time on endothelial function, which is cross-sectionally and prospectively associated with risk of cardiovascular disease, are unknown. PURPOSE: The purpose of this study was to examine the direct effects of breaking sitting time on femoral artery endothelial function. We hypothesized that breaks in sitting time will prevent the attenuation in endothelial function associated with prolonged sitting. METHODS: Eleven non-obese, healthy men (23.36±3.23 yrs) participated in two randomized 3 hr sitting trials. Subjects reported to the lab in a 6 hr fasted state. Subjects sat on a cushioned Chair: with their legs perpendicular to the floor, with feet flat on the ground. In the prolonged sitting (SIT) trial, subjects were seated for 3 hrs without moving their lower extremities. In the breaking sitting time trial (ACT), subjects sat similar to the SIT trial, but walked on a treadmill for 5 min at 2 mph at 0:30 min, 1:30 hr and 2:30 hr. Superficial femoral artery (SFA) flow mediated dilation (FMD) was assessed as a measure of endothelial function at baseline, 1hr, 2hr and 3hr in each trial. Descriptive statistics were performed for subject characteristics and paired sample t-tests were performed to examine the differences at each time point between SIT and ACT trial. RESULTS: There was no significant difference between the SFA FMD% at baseline (SIT: 4.82±3.95; ACT: 4.49±2.29, P=.776). However there were significant differences at 1 hr (SIT 0.47±0.88; ACT 5.04±2.85, P=0.001), 2hr (SIT 1.64±1.16; ACT 5.28± 5.05, P=0.045) and 3hr (SIT2.26±2.25; ACT 6.91±4.5, P=0.004) with an effect of ACT to prevent the reduction in FMD associated with SIT. CONCLUSION: Three hours of continuous sitting resulted in a significant impairment in superficial femoral artery endothelial function. When breaks with brief modest activity were introduced during the sitting time, this reduction in endothelial function was prevented. Breaking sitting time may be a physiologically beneficial cost effective way of maintaining vascular health in the sedentary population.