title: Rapid onset vasodilation with single muscle contractions in the leg: influence of age.
abstract: The influence of aging on contraction-induced rapid vasodilation has been well characterized in the forearm. We sought to examine the impact of aging on contraction-induced rapid vasodilation in the leg following single muscle contractions and determine whether potential age-related impairments were similar between limbs (leg vs. arm). Fourteen young (23 ± 1 years) and 16 older (66 ± 1 years) adults performed single leg knee extensions at 20%, 40%, and 60% of work rate maximum. Femoral artery diameter and blood velocity were measured using Doppler ultrasound. Limb vascular conductance (VC) was calculated using blood flow (mL·min(-1)) and mean arterial pressure (mmHg). Peak and total vasodilator responses in the leg (change [Δ] in VC from baseline) were blunted in older adults by 44-50% across exercise intensities (P < 0.05 for all). When normalized for muscle mass, age-related differences were still evident (P < 0.05). Comparing the rapid vasodilator responses between the arm and the leg of the same individuals at similar relative intensities (20% and 40%) reveals that aging influences peak and total vasodilation equally between the limbs (no significant age × limb interaction at either intensity, P = 0.28-0.80). Our data demonstrate that (1) older adults exhibit an attenuated rapid hyperemic and vasodilator response in the leg; and (2) the age-related reductions in rapid vasodilation are similar between the arm and the leg. The mechanisms contributing to the age-related differences in contraction-induced rapid vasodilation are perhaps similar to those seen with the forearm model, but have not been confirmed.
authors: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine University of Iowa, Iowa City, Iowa.
authors: William E
authors: WE
authors: Hughes
authors: Department of Anesthesia, Carver College of Medicine University of Iowa, Iowa City, Iowa.
authors: Kenichi
authors: K
authors: Ueda
authors: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine University of Iowa, Iowa City, Iowa.
authors: David P
authors: DP
authors: Treichler
authors: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine University of Iowa, Iowa City, Iowa darren-casey@uiowa.edu.
authors: Darren P
authors: DP
authors: Casey
keywords: Aging; exercise; hyperemia; limb; vasodilation