Elevated blood pressure is positively associated with atherosclerotic progression in healthy youth (22). A mechanism underpinning the development of hypertension is an impaired cardiac baroreflex sensitivity (BRS). In adults decreased BRS at rest has been shown to predict hypertension over 5 years (5), and BRS impairment measured using spontaneous indices is also observed in adolescents with prehypertension (6,10,11). Exercise training has been shown to improve BRS in healthy adults. In this population, increases in BRS were observed after 12 weeks of high-intensity interval exercise (HIIE) training (9) but not following moderate-intensity continuous training of similar duration (7,20), indicating that the intensity of exercise may be an important determinant of BRS adaptations. However, the influence of HIIE training on BRS in adolescents is currently unknown. To better understand the role of HIIE training on BRS in youth, the BRS gain can be reliably estimated as the autonomic and the vascular components (29). Although the effects of exercise on the autonomic and vascular determinants of BRS in youth remain unknown, several observations indicate that HIIE has potential to increase the BRS autonomic component. For example, cross-sectional associations between vigorous-intensity physical activity and resting autonomic function in adolescents have been reported (30), and a previous investigation has demonstrated significant increases in cardiac autonomic function following 2 weeks of HIIE in normotensive adolescents (1). Moreover, it has been recently shown that the autonomic compared to the vascular determinant of BRS is more responsive to acute HIIE and hyperglycemia in healthy adolescents (27,28). Therefore, it can be reasoned that resting cardiac BRS may be improved, thus reflecting increases in its autonomic determinant following HIIE training. In contrast, it should also be considered that improvements in resting cardiac BRS in adolescents, via augmented vascular component, may not be observed following HIIE training. The vascular component can be assessed using common carotid artery (CCA) compliance (29). In adults, 12 weeks of aerobic training improved resting cardiac BRS that was positively associated with increases in CCA compliance (23). However, in youth whether training can improve CCA distensibility is as yet unclear due to an already elevated CCA distensibility in 12-year-old adolescents compared with adults aged 21 (18). Indeed, a physiological ceiling effect may exist in healthy arteries impeding further adaptations to CCA compliance following training (25). Altogether, these results imply that the vascular component of BRS is unlikely to improve following training. Additionally, a better understanding of training effects can be achieved by the imposition of a detraining period. For example, in adolescents`, improvements in resting heart rate variability (HRV), and arterial function at 24 hours were reversed after 72 hours following HIIE training cessation (1). These data show that detraining following HIIE training may reverse putative training-induced adaptations to resting cardiac BRS in youth. The aim of this study was to investigate in healthy adolescents the effects of 4 weeks of HIIE training and 2 weeks of detraining on resting cardiac BRS and its autonomic and vascular determinants. We hypothesized that HIIE training would improve cardiac BRS due to a significant increase in its autonomic component with no observable effects on the vascular component. We also reasoned that improvements in cardiac BRS after training would be lost following 2 weeks of training cessation in healthy adolescents.
© Copyright 2022 Pediatric Exercise Science. Human Kinetics. Alle Rechte vorbehalten.