Dose-Response Effects of High-Intensity Interval Training on Body Fat, Blood Pressure, and Cardiorespiratory Fitness in Adolescents: A School-Based Randomized Controlled Trial with Responder Analysis
Question
Do 6, 8, and 10 minute school-based HIIT sessions produce dose-response changes in body fat percentage, systolic and diastolic blood pressure, and VO2max among adolescents, including adolescents previously classified as non-responders?
Summary
This school-based follow-up trial tested whether adolescents who had previously shown little or no response to HIIT could improve after a modified six-week Tabata-style program using 6, 8, or 10 minute HIIT sessions during physical education classes. Body fat percentage and blood pressure did not show clear group-level dose differences, but VO2max improved most consistently with the 10 minute sessions. Bayesian responder analyses suggested substantial individual variability and showed that many prior non-responders became responders after the modified intervention, especially for VO2max and systolic blood pressure.
Methodology
- Adolescents in the PEER-HEART school project, including prior HIIT non-responders and prior responders used as a control reference.
- 137 participants.
- Bodyweight/calisthenic and plyometric movement pairs.
- Work intervals: 20 seconds maximal effort.
- Recovery: 10 seconds passive rest.
- Intensity: Maximal effort; heart rate monitored with Polar devices.
- 10 minute warm-up plus 6, 8, or 10 minute HIIT main set.
- 2 sessions per week.
- 6 weeks.
- School-based randomized follow-up intervention with three HIIT duration arms, one non-intervention control group, and a stable responder control reference group; Bayesian responder classification and regression analyses were used.
- VO2max, Body fat percentage, Systolic and diastolic blood pressure, and Responder status were tracked.
Outcomes
VO2max
VO2max improved over time, with the strongest and most consistent effects reported for the 10 minute HIIT and CON-Rs groups.
Time F(1,127)=31.239, p<0.001; duration x time F(4,127)=25.900, p<0.001; duration effect approached significance F(4,127)=2.401, p=0.053.
Body fat percentage
BF% showed a main effect of time but no significant duration effect or duration-by-time interaction; post hoc pre-post comparisons in groups were not significant after correction.
Time F(1,127)=11.730, p<0.001; duration F(4,127)=1.161, p=0.331; duration x time F(4,127)=0.645, p=0.632.
Blood pressure
Group-level analyses did not show significant HIIT duration effects for SBP or DBP over time.
SBP time p=0.587 and duration x time p=0.907; DBP time p=0.900 and duration p=0.815.
Prior non-responder improvement
Many prior non-responders improved after the modified intervention; final Bayesian responder proportions ranged from 53.2% for VO2max to 68.4% for DBP.
McNemar significant for SBP p<0.001 and VO2max p<0.001; GEE prior non-responsive outcome OR=2.46, 95% CI 1.37-4.43, p=0.003.
Insights
- A 20:10 Tabata-style bodyweight format can fit into short school PE windows and still produce measurable aerobic changes.
- Extending the main set toward 10 minutes may be useful when the target is VO2max adaptation, but evidence for fat or blood-pressure dose-response was weak.
- Responder monitoring matters because some adolescents improve even when group-level effects are modest.
Limitations
- No long-term follow-up.
- Maturation stage and BMI were not stratified.
- Minor maturation changes across the six-month interval may have contributed to variability.
- Some heart-rate data were missing and imputed.
- Results are from supervised school PE and may not generalize to unsupervised settings.
Safety
- Safety and adherence details were not reported in the paper.