Vascular adaptation to 4 wk of deconditioning by unilateral lower limb suspension

Abstract

Physical inactivity or deconditioning is an independent risk factor for atherosclerosis and cardiovascular disease. In contrast to exercise, the vascular changes that occur as a result of deconditioning have not been characterized. We used 4 wk of unilateral lower limb suspension (ULLS) to study arterial and venous adaptations to deconditioning. In contrast to previous studies, this model is not confounded by denervation or microgravity. Seven healthy subjects participated in the study. Arterial and venous characteristics of the legs were assessed by echo Doppler ultrasound and venous occlusion plethysmography. The diameter of the common and superficial femoral artery decreased by 12% after 4 wk of ULLS. Baseline calf blood flow, as measured by plethysmography, decreased from 2.1 +/- 0.2 to 1.6 +/- 0.2 ml.min(-1).dl tissue(-1). Both arterial diameter and calf blood flow returned to baseline values after 4 wk of recovery. There was no indication of a decrease in flow-mediated dilation of the superficial femoral artery after ULLS deconditioning. This means that functional adaptations to inactivity are not simply the inverse of adaptations to exercise. The venous pressure-volume curve is shifted downward after ULLS, without any effect on compliance. In conclusion, deconditioning by 4 wk of ULLS causes significant changes in both the arterial and the venous system.

The effect of bed rest and an exercise countermeasure on leg venous function

“…Furthermore, reductions in capacitance were reported in spinal cord-injury individuals compared to control subjects (Frieden et al 1987;Hopman et al 1994), which is mainly attributed to the muscle atrophy and the possible concomitant vascular atrophy in the paralyzed legs. After bed rest, compliance of the popliteal vein remained unaltered, which is in line with previous deconditioning studies, using unilateral limb suspension (Bleeker et al 2005a) or bed rest (Bonde-Petersen et al 1994;Melchior and Fortney 1993). A possible reason that compliance is maintained during bed rest in the present study is the isolated location of the popliteal vein.…”

“…(2004), who reported an unaltered tibial and gastrocnemial vein diameter after 90 days of bed rest. These findings do not correspond with the previous results of a decrease in cross-sectional area of the popliteal and femoral vein (Arbeille et al 1999(Arbeille et al , 2001) and the common result of a decreased venous volume variation after bed rest (Bleeker et al , 2005aChrist et al 2001;Louisy et al 1997). The arterial vascular system also presented diameter reductions after deconditioning (Bleeker et al 2005a, b;De Groot et al 2006), but these changes over time were remarkably larger than previously shown in the venous vascular system.…”

“…Both venous capacitance and compliance are major determinants in the vital functions of the venous system, and a numerous amount of studies have been performed to specify their role in orthostatic intolerance after bed rest and space flight in humans. To study the effect of physical deconditioning on the venous vascular system, several human deconditioning models have been used, such as leg immobilisation (Bleeker et al 2005a), space flight (Arbeille et al 2001;Fomina and Kotovskaia 2005;Watenpaugh et al 2001), bed rest (Arbeille et al 1999(Arbeille et al , 2001Belin de Chantemele et al 2004;Bleeker et al 2005b;Bonde-Petersen et al 1994;Buckey et al 1992;Christ et al 2001;Convertino et al 1989;Louisy et al 1997;Melchior and Fortney 1993;Xiao et al 2005) and spinal-cord injury (Frieden et al 1987;Hopman et al 1994;Wecht et al 2000). Sparse data on venous diameter show a reduction in cross-sectional area of femoral venous diameter after bed rest (Arbeille et al 1999(Arbeille et al , 2001), but no change in tibial and gastrocnemial venous diameter (Belin de Chantemele et al 2004).…”

A Causal Role for Endothelin-1 in the Vascular Adaptation to Skeletal Muscle Deconditioning in Spinal Cord injury

“…6,7 In several pathological conditions, such as pulmonary 8 and systemic essential hypertension, 9 heart failure, 10,11 atherosclerosis, and obesity, 12 ET-1 plasma levels are elevated and contribute to the increased vascular tone observed in these disease states. In models of skeletal muscle deconditioning, such as unilateral limb suspension 13 and bed rest, 14 vascular tone is also increased. In the present study, we hypothesize that the elevated vascular tone in deconditioned muscles can be explained by an augmented contribution of ET-1.…”

Rare case of autonomic instability of the lower limb presenting as painless Complex Regional Pain Syndrome type I following hip surgery: two case reports

“…In both of our patients, the symptoms occurred during non-weight bearing and subsided after weight bearing was commenced. Unilateral lower limb suspension experiments in normal patients have shown an increase in flow mediated dilatation of arteries of the lower limb along with a decrease in venous capacitance [6]. This mechanism may explain the vascular changes which were more intense with the foot in the dependent positions.…”