Rapid Onset Vasodilation in the Leg is Greater in Habitual Endurance Runners

Although the beneficial effects of habitual physical activity on the peripheral vasculature are well‐established, activity‐dependent differences in the blood flow response to single muscle contractions have been largely ignored. Therefore, the purpose of this study was to determine if habitual endurance running (average training volume > 50 miles/week for ≥ 3 years) alters contraction‐induced rapid vasodilation in a limb‐specific manner. Trained (n = 8, 24 ± 3 years) and untrained (n = 4, 24 ± 1 years) men performed 1‐s maximal voluntary contractions in the leg (dorsiflexion) and forearm (hand‐grip). A physical activity recall questionnaire and 7‐day accelerometer recordings were used to confirm differences in training status between groups (p < 0.001). Anterior tibial and brachial arterial blood flow (ml/min) were measured with Doppler ultrasound for 30‐s prior, during, and 90‐s following the muscle contraction. Trained men demonstrated a greater increase in arterial flow in the leg (peak 5.8 ± 0.66‐fold above rest) compared with untrained men (peak 3.5 ± 0.37‐fold above rest; p = 0.04). In contrast, postcontractile blood flow responses in the arm were similar despite training status (Trained: peak 2.8 ± 0.41‐fold above rest; Untrained: peak 3.2 ± 1.1‐fold above rest, p = 0.86). Our data demonstrate that the magnitude of the postcontractile blood flow response to brief muscle contractions is greater in the legs of habitual endurance runners compared with untrained men. Collectively, these findings indicate that quantification of physical activity is necessary to properly interpret differences in contraction‐induced rapid vasodilation due to aging or disease. Support or Funding Information Funding: NIH/NIBIB T32 EB001628; CTSA UL1TR000445