Characterizing rapid onset vasodilation to single muscle contractions in the leg in humans (705.10)

Abstract

Rapid onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not been characterized in the leg. Given known vascular differences between arms and legs as well as the greater susceptibility of legs to atherosclerosis, we sought to characterize ROV in the leg. To do this, 9 healthy men performed random ordered single muscle contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) in the leg (knee extension) and forearm (handgrip). Continuous blood flow (BF) measures were made via duplex Doppler‐ultrasound from the brachial and femoral artery during 15 sec prior to and 45 sec after release of each contraction. Three trials were performed at each intensity. Limb BF was normalized to lean mass of forearm and thigh region through DEXA. Single muscle contractions produced an intensity dependent increase in BF, peaking ~4 sec post contraction in both limbs. Initial BF responses (1st heart beat) were significantly greater in the leg, most notable at lower MVC intensities (e.g. 10%‐MVC initial response; Arm=+19±5% vs. Leg=+75±15%, P=0.01). However, peak changes in BF were similar between limbs for each contraction intensity (e.g. 60%‐MVC peak; Arm=+207±33% vs. Leg=+208±33%, P>0.05). These preliminary findings indicate that peak BF responses to single muscle contractions are similar between limbs establishing the presence of ROV in the leg.Grant Funding Source: NIH grant RO1 HL093167 (PJF)