Vasoconstrictor responsiveness in resting and contracting skeletal muscle following an acute bout of exercise: impact of aging

Long-term exercise training can attenuate sympathetic vasoconstriction in both resting and contracting skeletal muscle; however, the impact of an acute bout of exercise on vasoconstrictor responsiveness and the influence of aging is unknown. Therefore, we tested the hypothesis that an acute bout of exercise will blunt sympathetic-mediated vasoconstriction in resting and contracting skeletal muscle of young and older adults. Twenty-one adults (10 young: 23 ± 5 yr and 11 older: 65 ± 8 yr) performed a rest and a rhythmic handgrip exercise trial before and after either 30 min of cycling exercise (60%-65% age-predicted maximal heart rate) or a time control period (seated rest). Lower body negative pressure (-30 mmHg) was applied during each trial to induce sympathetic-mediated vasoconstriction. Forearm blood flow (FBF; mL/min) was assessed via Doppler ultrasound and forearm vascular conductance (FVC; mL·min^-1·100 mmHg^-1) was calculated as the quotient of FBF and mean arterial pressure (mmHg). The acute bout of cycling exercise did not change vasoconstrictor responsiveness (% change FVC) in resting skeletal muscle in either age group (<i>P</i> > 0.05). However, vasoconstrictor responsiveness was attenuated in contracting skeletal muscle following the acute bout of cycling exercise in the entire group (-11.0 ± 5.7 to -8.2 ± 5.1%, <i>P</i> < 0.001), as well as separated by age (young: -6.7 ± 3.2 to -5.0 ± 4.0%, older: -14.9 ± 4.6 to -11.0 ± 4.2%, <i>P</i> < 0.01 for both). Our data indicate that an acute bout of exercise does not change vasoconstrictor responsiveness in resting skeletal muscle but enhances functional sympatholysis in young and older adults.<b>NEW & NOTEWORTHY</b> Data from the current study demonstrate that a single bout of exercise can enhance functional sympatholysis in contracting skeletal muscle. In addition, despite aging being associated with reduced functional sympatholysis, older adults experienced similar improvements following an acute bout of exercise as their young counterparts. These results suggest that the previously reported exercise training-induced improvements in functional sympatholysis may occur as early as the first session.