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

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; LFgain ) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain /AC was used as the autonomic component. LFgain 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. LFgain /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.