Effect of increased venous blood flow with acute passive heating on volume and compliance in the calf vein in young adults

Arterial endothelial function-impairment of which is a risk factor for cardiovascular disease-increases after acute passive heating; however, whether venous properties (volume and compliance) also increase remains unclear. Moreover, it is unknown whether venous congestion induced by proximal thigh cuff inflation and passive heating exerts opposing effects on the venous properties. Therefore, in 21 young healthy adults, we determined the acute effects of passive heating (42°C) of the left leg and concurrent cuff inflation (80-110 mmHg) of the right leg for 40 min on venous properties. Specifically, before (Pre) and 60 min after (Post 60) the single manipulation, the venous volume and compliance in both legs were determined from the change in calf volume during a cuff deflation protocol. After passive heating, the calf venous compliance decreased (Pre, 0.090 ± 0.032 mL/dL/mmHg; Post 60, 0.084 ± 0.031 mL/dL/mmHg; p < 0.05), but calf venous volume did not change (Pre, 3.18 ± 1.10 mL/dL; Post 60, 3.01 ± 1.14 mL/dL; p > 0.05). While the volume (Pre, 3.32 ± 1.08 mL/dL; Post 60, 3.19 ± 0.86 mL/dL; p > 0.05) and compliance (Pre, 0.091 ± 0.028 mL/dL/mmHg; Post 60, 0.092 ± 0.033 mL/dL/mmHg; p > 0.05) in calf veins did not alter after thigh cuff inflation. These results suggest that acute passive heating decreases calf venous compliance with no change in calf venous volume, while thigh cuff inflation does not alter volume and compliance in the calf veins in healthy young adults.