[Doctor Snuggles]

Effect of Prolonged Sitting and Breaks in Sitting Time on Endothelial Function.
Thosar, Saurabh S.; Bielko, Sylvanna L.; Mather, Kieren J.; Johnston, Jeanne D.; Wallace, Janet P.
Published Ahead-of-Print
Collapse BoxAbstract
Sitting time (ST) is associated with cardiovascular disease risk factors whereas breaking ST has been reported to be beneficial for reducing cardiovascular risk.

PURPOSE: To examine the effects of breaking ST on superficial femoral artery (SFA) endothelial function. Hypotheses: 1) prolonged sitting would induce endothelial dysfunction and changes in shear forces and 2) breaking sitting time with brief periods of activity would prevent attenuation in endothelial function.

METHODS: Twelve non-obese men (24.2+/-4.2 yrs.) participated in two randomized 3hr sitting trials. In the sitting (SIT) trial, subjects were seated on a firmly cushioned chair for 3hr 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 five min at 2 miles[middle dot]hr-1 at 30min, 1hr 30min, and 2hr 30min during the sitting interval. SFA flow mediated dilation (FMD) was assessed at baseline, 1hr, 2hr, and 3hr in each trial. Statistical analyses were performed using dependent variables SFA FMD, and shear rates. Significance was set at p<=0.05.

RESULTS: In the SIT trial, there was a significant decline in SFA FMD from baseline to 3hr (baseline: 4.72+/-3.78%, 1hr: 0.52+/-0.85%, 2hr: 1.66+/-1.11%, 3hr: 2.2+/-2.15; p<0.05 by ANOVA) accompanied by a decline in mean shear rate (MSR) and antegrade shear rate (ASR), but no difference in SRauc. By 2-way repeated measures ANOVA, ACT prevented the sitting-induced decline in FMD, (baseline: 4.5+/-2.3%, 1hr: 5.04+/-2.85%, 2hr: 5.28+/-5.05%, 3hr: 6.9+/-4.5%) along with no decline in shear rates.

CONCLUSION: Three hours of sitting resulted in a significant impairment in shear rate and SFA FMD. When light activity breaks were introduced hourly during sitting, the decline in FMD was prevented.

(C) 2014 American College of Sports Medicine

http://journals.lww.com/acsm-msse/pa...&type=abstract