Uncovering intensity trajectory patterns and their association with blood pressure adaptation following school-based high-intensity interval exercise in adolescents: Wroclaw PEER-HEART study

Introduction This study examined intensity patterns during school-based high-intensity interventions and their association with blood pressure (BP) adaptation in adolescents. Methods A total of 145 students aged 16 (69 boys) participated in either traditional HIIT or a plyometric variant (HIPT) over eight weeks (16 sessions). Exercise intensity was calculated using the heart rate reserve method. Outcomes of interest were systolic and diastolic blood pressure (SBP, DBP, respectively). Blood pressure responders (Rs) and non-responders (NRs) were identified using a Bayesian approach. Results Latent class mixed models revealed three distinct intensity trajectories: Class 1 (low-intensity declining trajectory), Class 2 (moderate-intensity declining trajectory), and Class 3 (high-intensity U-shaped trajectory). Although no significant unadjusted association was found between responder status and trajectory class, logistic regression indicated that individuals in Class 2 had higher odds of being classified as SBP responders (OR = 3.86, p = 0.04), whereas Class 3, male sex, and HIPT participation were associated with lower odds of meeting the responder criterion. In contrast, linear regression analyses demonstrated that participants in Classes 2 and 3 exhibited greater mean reductions in both SBP and DBP than those in Class 1 ( p < .01), highlighting that responder classification and the magnitude of blood pressure change reflect different aspects of adaptation. Trajectory class was the strongest predictor of BP change. HIPT was associated with greater DBP reductions ( p = .006), whereas sex was not a significant predictor in the continuous models. Discussion These findings indicate that adolescents may follow different patterns of exercise intensity across a school-based intervention and that these patterns may be associated with blood pressure adaptation. Monitoring session-by-session exercise intensity may therefore provide information beyond the average intensity of the entire program. However, further studies are required before trajectory-based monitoring can be translated into specific recommendations for school practice.