Effects of autonomic disruption and inactivity on venous vascular function

The effects of autonomic disruption and inactivity were studied on the veno us vascular system. Forty-eight subjects, 24 with spinal cord injury (SCI) and 12 sedentary and 12 active able-bodied controls, participated in this s tudy. Peripheral autonomic data were obtained to estimate sympathetic vasom otor control [low-frequency component of systolic blood pressure (LFSBP)] V ascular parameters were determined using strain-gauge venous occlusion plet hysmography: venous capacitance (VC), venous emptying rate (VER), and total venous outflow (VOt). An additional vascular parameter was calculated: ven ous compliance [(VC/occlusion pressure) x 100]. VC and VOt were significant ly different (SCI < sedentary < active). VER adjusted for VC was not differ ent for any group comparison, whereas venous compliance was significantly l ower in the SCI group than in the able-bodied groups and in the sedentary g roup compared with the active group. Regression analysis-for the total grou p revealed a significant relationship between LFSBP and venous compliance ( r = 0.64, P < 0.0001). After controlling for LFSBP through analysis of cova riance, we found that mean differences for all venous vascular parameters d id not change from unadjusted mean values. Our findings suggest that in sub jects with SCI, the loss of sympathetic vasomotor tone contributes more tha n inactivity tp reductions in venous vascular function. Heightened VC, VOt, vasomotor tone, and venous compliance in the active group compared with th e sedentary group imply that regular endurance training contributes to opti mal venous vascular function and peripheral autonomic integrity.