Knee-high compression socks minimize head-up tilt-induced cerebral and cardiovascular responses following dynamic exercise.

Abstract

In healthy individuals during a non-exercised state, knee-high compression socks (CS) may reduce the magnitude of lower limb venous pooling during orthostasis but are not effective at minimizing the incidence of pre-syncopal symptoms. However, exaggerated reductions in cerebral blood flow velocity (CBV) and cardiac stroke volume (SV) occur during passive head-up tilt (HUT) testing following dynamic exercise. It is unknown if CS can minimize post-exercise HUT-induced decrements in CBV and SV in this population. To test the hypothesis that CS will attenuate the reductions in SV and CBV during 60° HUT following 60minutes of moderate-intensity (60% VO2 peak) cycling exercise. Ten healthy volunteers (22.6±2.1years, 24.1±2.5kg/m2 ) completed pre- and post-exercise 15-minute HUT tests during randomized CS and Control (no CS) conditions. Changes in blood pressure (finger plethysmography), SV (Modelflow® method), and CBV (Transcranial Doppler) were measured during HUT and preceding supine rest periods. Pre-exercise HUT-induced similar (all, P>.47) reductions in SV (Control; -23.1±11.5%, CS; -20.5±10.9%) and CBV (Control; -18.1±6.3%, CS; -15.3±9.0%). However, larger post-exercise decreases in SV and CBV during HUT were observed in the Control versus CS condition. Specifically, CS attenuated the drop in SV (Control: -32.9±5.6%, CS: -24.3±11.6%; P=.01) and CBV (Control: -25.1±5.8%, CS: -17.6±7.8%; P=.02) during the post-exercise HUT test. These results indicate that CS attenuated HUT-induced reductions in SV and CBV following moderate-intensity cycling exercise and suggest that CS may be an effective countermeasure to reduce the incidence of post-exercise syncope in vulnerable populations.