Effect of prolonged sitting and breaks in sitting time on endothelial function

Area of Science:

• Cardiovascular Physiology
• Exercise Science
• Vascular Biology

Background:

• Prolonged sitting (ST) is linked to cardiovascular disease risk factors.
• Interrupting sedentary time with physical activity may mitigate cardiovascular risks.

Purpose of the Study:

• To investigate the impact of interrupting sitting time on superficial femoral artery (SFA) endothelial function.
• To test if brief activity breaks prevent endothelial dysfunction caused by prolonged sitting.

Main Methods:

• Twelve healthy men underwent two 3-hour randomized trials: continuous sitting (SIT) and sitting with intermittent walking breaks (ACT).
• Superficial femoral artery (SFA) flow-mediated dilation (FMD) and shear rates were measured at intervals.
• ACT involved 5-minute treadmill walks at 2 mph at 30 min, 1.5 h, and 2.5 h during the sitting period.

Main Results:

• Continuous sitting significantly reduced SFA FMD and shear rates over 3 hours.
• Intermittent activity breaks (ACT) successfully prevented the decline in SFA FMD.
• Shear rates remained stable in the ACT trial, unlike in the SIT trial.

Conclusions:

• Three hours of uninterrupted sitting impairs vascular function, specifically SFA endothelial function.
• Hourly short bouts of light activity during sitting effectively preserve endothelial function.
• Intermittent activity breaks are a viable strategy to counteract the negative vascular effects of sedentary behavior.