Effect Of Impact During High-intensity Interval Exercise On Bone Markers In Female Adolescents

PURPOSE: The physical impact during exercise is considered the primary variable for enhancing bone properties during adolescence. Conversely, it has been suggested that high-intensity interval exercise (HIIE) may induce similar changes in bone markers regardless of the impact. Nevertheless, the effects of HIIE with and without impact on bone markers have not been investigated in adolescents. Thus, we aimed to examine the acute effect of HIIE performed with and without impact on bone markers of formation (i.e., P1NP) and resorption (i.e., CTX-I) in female adolescents. METHODS: Eleven adolescents at post-peak height velocity (PHV), aged 15 to 18.9 years, performed two HIIE (cycling and running) trials in random order (cross-over design). Each participant performed a progressive incremental test for each mode of HIIE. The maximal speed and power achieved in these tests were set as the workload for the HIIE trials. For each trial, participants completed 8 bouts of 1 minute of work separated by 1 minute of rest. Adolescents were instructed to have a standardized breakfast 1 hour before the exercise session and blood samples were taken before exercise, as well as 5 and 60 minutes after exercise. Serum concentrations of P1NP and CTX-1 were analyzed using a chemiluminescence assay. A two-way ANOVA with repeated measures, considering PHV and leg lean mass as covariates, tested the effects of the HIIE mode (running or cycling), time (pre, 5 min, 60 min post-exercise), and their interaction. RESULTS: A significant mode*time interaction was observed in P1NP (p = 0.005). In the running mode, P1NP significantly increased by 18% from 97.1 ± 39.9 mcg/L at baseline to 114.3 ± SD = 47.0 mcg/L at 5 min post-exercise, returning to baseline levels after 60 min while cycling did not induce any significant changes. Regarding CTX-1, no significant effects were observed in either running or cycling. CONCLUSION: HIIE associated with impact (running) induced significant changes in bone formation marker, which was not the case when HIIE was performed without impact (cycling), suggesting that the intensity of exercise alone does not seem to induce a significant bone response in adolescent females. Sao Paulo Research Foundation (FAPESP)