Calf exercise-induced vasodilation is blunted in healthy older adults with increased walking performance fatigue

Vascular aging as measured by central arterial stiffness contributes to slow walking speed in older adults, but the impact of age-related changes in peripheral vascular function on walking performance is unclear. The aim of this study was to test the hypothesis that calf muscle-specific vasodilator responses are associated with walking performance fatigue in healthy older adults. Forty-five older (60-78yrs) adults performed a fast-paced 400m walk test. Twelve of these adults exhibited fatigue as defined by slowing of walking speed (≥0.02m/s) measured during the first and last 100m segments of the 400m test. Peak calf vascular conductance was measured following 10min of arterial occlusion using strain-gauge plethysmography. Superficial femoral artery (SFA) vascular conductance response to graded plantar-flexion exercise was measured using Doppler ultrasound. No difference was found for peak calf vascular conductance between adults that slowed walking speed and those that maintained walking speed (p>0.05); however, older adults that slowed walking speed had a lower SFA vascular conductance response to calf exercise (at highest workload: slowed group, 2.4±0.9 vs. maintained group, 3.6±0.9ml/kg/min/mmHg; p<0.01). Moreover, the initial increase in SFA vascular conductance from rest to exercise was positively correlated with the change in walking speed for all adults (rho=0.41, p=0.005). In conclusion, these results suggest that calf exercise hemodynamics are associated with walking performance fatigability in older adults.