Brachial and Femoral Artery Responses to Prolonged Sitting
Brachial and Femoral Artery Responses to Prolonged Sitting
Introduction It is unknown if there are limb differences in vascular function during prolonged sitting.
Purpose This study was designed to test whether the effects of prolonged sitting on brachial artery (BA) and the superficial femoral artery (SFA) are similar.
Methods Twelve men (24.2 ± 4 yrs.) participated in a 3 hr prolonged sitting trial (SIT). SFA and BA flow mediated dilation (FMD) and respective flow patterns were measured at baseline, 1 hr, 2 hr and 3 hr.
Results By a one-way ANOVA there was a significant decline in SFA FMD during 3 hrs of SIT (p < 0.001). Simultaneously, there was a significant decline in antegrade (p = 0.04) and mean (0.037) shear rates. By a one way ANOVA there were no significant differences in BA FMD during 3 hrs of sitting. There were no changes in the shear rates in the BA except for a significant decrease in antegrade shear rate (p = 0.029) and a significant increase in oscillatory shear index (p = 0.034) during 3 hrs of sitting. Furthermore, there was no correlation between BA and SFA FMD measurements.
Conclusion Three hours of sitting resulted in impaired SFA FMD but not BA FMD. Although 3 hours of sitting did not impair BA FMD, it impaired shear patterns in the BA.
The presence of sedentary behavior is a major concern in today's society. There are numerous sitting opportunities throughout the day and the average sitting time for American adults is ~8 hr/day. Sitting creates a unique anatomical and physiological milieu in the legs including bends in the femoral and popliteal artery, increased viscosity, blood pressure and decrease in arterial shear rates. Interestingly in humans, lower extremities exhibit an increased distribution of atherosclerosis as compared to the upper extremities. There may be various reasons for this disparity. For example, one of the mechanisms may be increased hydrostatic pressure on the lower extremities on assuming an upright posture while seating or standing. Because of the increased presence of sitting, we recently studied the effects of 3 hours of sitting on lower extremity (superficial femoral artery [SFA]) endothelial function and discovered that 3 hrs of prolonged sitting decreased mean and antegrade shear rates in the SFA and also impaired endothelial function measured by flow mediated dilation (FMD). It is known that decrease in antegrade shear rate may promote a pro-atherogenic environment. In addition, FMD is a very good predictor of cardiovascular disease and is impaired even before the presence of frank atherosclerosis. Nitric oxide which is a key regulator of endothelial function is synthesized in the presence of enzymes known as nitric oxide synthases. Low shear stresses during prolonged sitting decrease the expression of nitric oxide synthase and this may also lead to impairment in endothelial function, putting the vasculature at risk of atherosclerosis. It is interesting to note that increases in shear stresses leads to betterment in endothelial function. In fact lower extremity exercise also improves brachial artery endothelial function which may explain the antiatherogenic effect of exercise However, at the lower end of the physical activity continuum, it is unknown if lower extremity inactivity affects upper extremity endothelial function. In the presence of our recent findings on the impairment of endothelial function on sitting, it is interesting to study whether upper extremity (brachial artery [BA]) endothelial function is also affected on prolonged sitting. The purpose of this study was to investigate if the effects of prolonged sitting on BA and SFA are similar.
Abstract and Introduction
Abstract
Introduction It is unknown if there are limb differences in vascular function during prolonged sitting.
Purpose This study was designed to test whether the effects of prolonged sitting on brachial artery (BA) and the superficial femoral artery (SFA) are similar.
Methods Twelve men (24.2 ± 4 yrs.) participated in a 3 hr prolonged sitting trial (SIT). SFA and BA flow mediated dilation (FMD) and respective flow patterns were measured at baseline, 1 hr, 2 hr and 3 hr.
Results By a one-way ANOVA there was a significant decline in SFA FMD during 3 hrs of SIT (p < 0.001). Simultaneously, there was a significant decline in antegrade (p = 0.04) and mean (0.037) shear rates. By a one way ANOVA there were no significant differences in BA FMD during 3 hrs of sitting. There were no changes in the shear rates in the BA except for a significant decrease in antegrade shear rate (p = 0.029) and a significant increase in oscillatory shear index (p = 0.034) during 3 hrs of sitting. Furthermore, there was no correlation between BA and SFA FMD measurements.
Conclusion Three hours of sitting resulted in impaired SFA FMD but not BA FMD. Although 3 hours of sitting did not impair BA FMD, it impaired shear patterns in the BA.
Introduction
The presence of sedentary behavior is a major concern in today's society. There are numerous sitting opportunities throughout the day and the average sitting time for American adults is ~8 hr/day. Sitting creates a unique anatomical and physiological milieu in the legs including bends in the femoral and popliteal artery, increased viscosity, blood pressure and decrease in arterial shear rates. Interestingly in humans, lower extremities exhibit an increased distribution of atherosclerosis as compared to the upper extremities. There may be various reasons for this disparity. For example, one of the mechanisms may be increased hydrostatic pressure on the lower extremities on assuming an upright posture while seating or standing. Because of the increased presence of sitting, we recently studied the effects of 3 hours of sitting on lower extremity (superficial femoral artery [SFA]) endothelial function and discovered that 3 hrs of prolonged sitting decreased mean and antegrade shear rates in the SFA and also impaired endothelial function measured by flow mediated dilation (FMD). It is known that decrease in antegrade shear rate may promote a pro-atherogenic environment. In addition, FMD is a very good predictor of cardiovascular disease and is impaired even before the presence of frank atherosclerosis. Nitric oxide which is a key regulator of endothelial function is synthesized in the presence of enzymes known as nitric oxide synthases. Low shear stresses during prolonged sitting decrease the expression of nitric oxide synthase and this may also lead to impairment in endothelial function, putting the vasculature at risk of atherosclerosis. It is interesting to note that increases in shear stresses leads to betterment in endothelial function. In fact lower extremity exercise also improves brachial artery endothelial function which may explain the antiatherogenic effect of exercise However, at the lower end of the physical activity continuum, it is unknown if lower extremity inactivity affects upper extremity endothelial function. In the presence of our recent findings on the impairment of endothelial function on sitting, it is interesting to study whether upper extremity (brachial artery [BA]) endothelial function is also affected on prolonged sitting. The purpose of this study was to investigate if the effects of prolonged sitting on BA and SFA are similar.