12-Days of Unilateral Immobilization of the Lower Limb Alters Peripheral Arterial Compliance in a Healthy Population

Abstract

Physical inactivity or deconditioning is cited as an independent risk factor for cardiovascular disease. Few studies have characterized the effects of deconditioning on peripheral arterial properties. Furthermore, studies to date have not addressed the early time course of these adaptations. PURPOSE: To follow the time course of peripheral and central compliance using a unilateral immobilization model in young healthy men and women. METHODS: 15 healthy participants (8 female, 7 male; age: 20.6 ± 0.7) were monitored for compliance/distensibility alterations in peripheral (common femoral, popliteal) and central (carotid) arteries over the course of 12-Days of unilateral lower limb immobilization. Measurements of arterial pulse pressure were obtained using applanation tonometry both at the carotid artery for central measurements and in the radial artery for peripheral measurements, while ultrasound imaging was used to determine within heart cycle changes in arterial cross-sectional area. Participants were monitored before (PRE), at 6-days (6D), and at 12-days (12D) following immobilization. Arterial compliance was calculated based on the cross-sectional area change of the artery for a give change in expanding pressure. The non-immobilized leg was used as a control comparison leg. A two-way repeated measure ANOVA was used to compare immobilization effects. RESULTS: Carotid artery compliance did not change at any time-point (p>0.05) whereas alterations in the peripheral arteries were apparent. In the immobilized leg, compliance declined throughout the immobilization period both in the femoral (0.117 ±0.01 vs. 0.096 ±0.01 vs. 0.081 ± 0.01, p<0.05) and popliteal (0.055 ± 0.003 vs. 0.043 ±0.004 vs. 0.037 ± 0.004, p<0.05) arteries. The non-immobilized limb showed a stabilizing effect (Femoral: 0.114 ±0.01 vs. 0.102 ±0.01 vs. 0.102 ± 0.01, p<0.05, popliteal: 0.068 ± 0.009 vs. 0.059 ± 0.006 vs. 0.055 ± 0.007, p<0.05) as the 6 and 12 day time-points showed significant differences from PRE values but were not different from each other. CONCLUSIONS: Lower limb immobilization has the effect of reducing arterial compliance in both limbs. This is likely related to an overall reduction in activity. Supported by NSERC and CIHR