Effect of an acute bout of exercise on functional sympatholysis: Impact of aging

Attenuation of sympathetically mediated vasoconstriction in contracting skeletal muscles (i.e. functional sympatholysis) helps to ensure adequate blood flow during exercise. However, functional sympatholysis is reduced with aging. While long-term exercise training can attenuate sympathetic vasoconstriction in both resting and contracting skeletal muscle, the impact of an acute bout of exercise on vasoconstrictor responsiveness and the influence of aging are unknown. Therefore, we tested the hypothesis that an acute bout of exercise will blunt sympathetically mediated vasoconstriction in resting and contracting human skeletal muscle of young and older adults. A total of 21 (10 Young; 23 ± 5 yr. and 11 Older; 65 ± 8 yr.) healthy adults performed a rest and a rhythmic handgrip exercise (20 contractions per min at 15% maximal voluntary contraction) trial before and after either 30-min of cycling exercise (60-65% HRmax) or a time control period (TC; sitting on the cycle without pedaling). Lower body negative pressure (LBNP) was applied at -30 mmHg during each rest and rhythmic handgrip exercise trial to induce sympathetic mediated vasoconstriction. Forearm blood flow (FBF; ml/min) was assessed via Doppler ultrasound and forearm vascular conductance (FVC; ml/min/100mmHg) was calculated as the quotient of FBF and mean arterial pressure (mmHg). Percent (%) reduction in FVC was used as the standard index to compare vasoconstrictor responses to LBNP-induced vasoconstriction between each respective rest and handgrip trial (pre vs. post cycling exercise or TC). The acute bout of cycling exercise did not change vasoconstrictor responsiveness in resting skeletal muscle in the Young (Cycling: -37.6 ± 8.8 to -35.8 ± 8.7%; TC: -39.8 ± 6.1 to -40.1 ± 8.5%, condition x time P=0.73) or Older (Cycling: -34.6 ± 13.7 to -33.5 ± 12.4%; TC: -33.6 ± 10.7 to -32.1 ± 10.0%, condition x time P=0.65) groups. However, vasoconstrictor responsiveness was attenuated in contracting skeletal muscle in Young (Cycling: -6.7 ± 3.2 to -5.0 ± 4.0%; TC: -6.6 ± 4.3 to -6.4 ± 4.7%, condition x time p<0.05) and Older (Cycling: -14.9 ± 4.6 to -11.0 ± 4.2%; TC: -14.6 ± 4.6 to -14.4 ± 4.2%, condition x time p<0.05) groups following an acute bout of cycling exercise. The amount of change in functional sympatholysis following an acute bout of cycling exercise did not differ between the young and older groups (group x time, P=0.13). Our data indicate that an acute bout of exercise does not change vasoconstrictor responsiveness in resting skeletal muscle but enhances functional sympatholysis to a similar extent in young and older adults. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.