Are Mechanisms of Rapid Onset Vasodilation Sensitive to Exercise Training?

Rapid vasodilation (ROV) is a feedforward process that increases blood flow to exercising muscles at the onset of exercise. Whether exercise training can enhance rapid vasodilation in a healthy, young adults is unknown. PURPOSE: To investigate the influence of training status on ROV in healthy, young people. METHODS: 8 trained participants (TRN; all males) and 8 sedentary participants (SED; biological sex, age, and height matched with trained participants) completed 2 study visits (1 familiarization; 1 experimental visit). TRN: those with exercise training of ≥1 day/wk, including forearm-specific training, for 6+ months. SED: those who have not engaged in regular exercise for ≥ 6 months and activity level < 600 MET-min/wk (via international physical activity questionnaire). During the experimental visit, participants completed 2 trials of 5 different 1-second stimuli, each separated by 2 minutes of rest: 4 intensities of voluntary handgrip contraction (100% of a subject’s maximal voluntary contraction, 5kg, 10kg, and 15kg), and mechanical compression of the forearm (300mmHg). The order of stimuli in both trials was randomized separately, and participants were blinded to the order. Forearm blood flow (FBF, doppler and echo ultrasound) and mean arterial pressure (MAP, finger photoplethysmography) were acquired for 30 heartbeats immediately before and 30 heartbeats immediately after each stimulus. Each trial was averaged into a singular response. Vascular conductance (FVC, FBF/MAP × 100mmHg) was calculated. Δ FVCtotal (ml/100mmHg) was calculated as the integral of the absolute change in FVC across 30 heartbeats after a stimulus; Δ FVCpeak (ml/min/100mmHg) was determined to be the largest Δ FVC value observed within 30 heartbeats after a stimulus. RESULTS: Data are mean ± SD. TRN displayed greater Δ FVCtotal (Δ FVCtotal TRN: 80.04 ± 39.40 vs. SED: 31.64 ±11.99, p=0.006 r=0.683) and Δ FVCpeak (TRN: 315.12 ± 162.63 vs. SED: 151.98 ± 53.60, p=0.003 r=0.735) with large effect sizes when compared to SED counterparts in response to 100%MVC .TRN displayed greater Δ FVCtotal (TRN v SED; 5kg: 38.42 ± 14.48 vs. 20.69 ± 6.33, p=0.003 d=1.588; 10kg: 47.95 ± 14.76 vs. 25.70 ± 9.16, p=0.001 d=1.811; 15kg: 61.72 ± 24.84 vs. 27.65 ± 7.66, p=0.012 r=0.63) and Δ FVCpeak (TRN v SED: 5kg: 179.85± 53.60 vs. 105.09 ± 35.67, p=0.003 d=1.642; 10kg: 233.06 ± 63.07 vs. 125.28 ± 40.63, p< 0.001 d=2.032; 15kg: 250.51 ± 97.28 vs. 126.70 ± 37.71, p=0.021 r=0.578) with large effect sizes compared to SED in response to absolute-intensity voluntary contractions. Further, TRN also displayed greater Δ FVCtotal (TRN: 13.83 ± 6.36 vs. SED: 8.87± 4.62, p=0.048 d=0.892) and Δ FVCpeak (TRN: 86.21 ± 36.86 vs. SED: 56.45± 24.13, p=0.038 d=0.955) with large effect size compared to SED in response to a 300mmHg mechanical forearm compression. CONCLUSION: Our results indicate that trained participants demonstrated enhanced rapid vasodilation compared to sedentary individuals. These data indicate that all mechanisms of ROV including mechanical sensitive processes are enhanced by habitual exercise. This abstract was presented at the American Physiology Summit 2026 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.