Rapid Onset Vasodilation is Blunted with Aging: Evidence for Limb Specificity?

Abstract

We aimed to examine the impact of aging on rapid onset vasodilation (ROV) in the leg following single muscle contractions. Young (n=14; 23±1yr; 9M/5F) and older (n=14; 66±1yr; 10M/4F) adults performed single muscle contractions at 20%, 40%, and 60% work rate maximum for knee extension. Diameter and blood velocity were measured in the femoral artery using Doppler ultrasound. Limb vascular conductance (VC) was calculated using blood flow (mL/min), mean arterial pressure (mmHg) and normalized for muscle mass (kg). Older adults demonstrated lower peak and total contraction‐induced vasodilation in the leg across exercise intensities compared to young adults (P < 0.001). To explore limb specific differences, leg responses at 20% and 40% were compared to single contractions of the forearm (handgrip) within each subject. At 20%, both older and young adults had a higher ΔVC in the arm vs leg (Older: 90±7 vs. 49±4 mL/kg/min/100mmHg, P < 0.01; Young: 123±7 vs. 94±10 mL/kg/min/100mmHg, P < 0.05). Similarly, a higher ΔVC in the arm vs. leg was also observed at 40% in older and young adults (Older: 126 ± 9 vs. 62±5 mL/kg/min/100mmHg, P < 0.01; Young: 168±11 vs. 109±10 mL/kg/min/100mmHg, P < 0.05). Our data demonstrate that 1) aging blunts skeletal muscle contraction‐induced ROV in the leg and 2) when normalized for muscle mass, both young and older adults demonstrate a greater ROV in the arm compared to the leg.