Mechanisms of blood pressure control following acute exercise in adolescents: Effects of exercise intensity on haemodynamics and baroreflex sensitivity.

New Findings: What is the central question of this study? What are the autonomic and vascular components of the baroreflex during hypotension following different exercise intensities in adolescents? What is the main finding and its importance? Hypotension after high-intensity exercise lasted 60 min, whereas following moderate-intensity exercise, blood pressure was restored after 20 min. Stroke volume and peripheral resistance responses were different between intensities. Post both exercise intensities, baroreflex sensitivity was lowered mainly due to the autonomic component, which returned to baseline 60 min post-exercise. The different haemodynamic stimuli indicate potential differences in cardiovascular health benefits of exercise intensity in healthy adolescents.
Abstract: This work aimed to investigate the time course of changes in baroreflex sensitivity (BRS) and its vascular and autonomic components after different exercise intensities in adolescents. Thirteen male adolescents (age 13.9 ± 0.5 years) completed on separate days in a counterbalanced order (1) high-intensity interval exercise (HIIE): 8 × 1 min running at 90% of maximal aerobic speed with 75 s of active recovery; (2) moderate-intensity interval exercise (MIIE): 10-12 bouts of 1 min running at 90% of gas exchange threshold with 75 s of active recovery; and (3) resting as a control. Supine heart rate and blood pressure were monitored continuously at baseline, and 5 and 60 min following the conditions. A cross-spectral method (low frequency gain; LF _gain ) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LF _gain /AC was used as the autonomic component. LF _gain decreased 5 min post-exercise bouts (HIIE P < 0.001; MIIE P = 0.002), but returned to baseline at 60 min post-exercise. AC increased at 5 min post-exercise for all conditions (P = 0.048), and returned to baseline at 60 min post-exercise. LF _gain /AC decreased 5 min post-exercise bouts (HIIE P = 0.001; MIIE P = 0.004), but returned to baseline values at 60 min post-exercise. Mean arterial pressure was lowered by both exercise intensities at 5 min post-exercise, but remained decreased at 60 min post-exercise following HIIE only. In conclusion, BRS decreases 5 min following exercise in adolescents independent of exercise intensity and is mainly driven by a lowered autonomic response. At 60 min post-exercise, the ability of BRS to regulate blood pressure is restored after MIIE but not after HIIE, indicating exercise intensity-dependent mechanisms.
(© 2018 The Authors. Experimental Physiology © 2018 The Physiological Society.)