The Mediation Role of Fatness in Associations between Cardiorespiratory Fitness and Blood Pressure after High-Intensity Interval Training in Adolescents
Question
Do fatness measures mediate the association between baseline cardiorespiratory fitness and post-HIIT resting blood pressure in adolescents, and does sex moderate this mediation?
Summary
This secondary analysis of a school-based HIIT intervention found that, among non-hypertensive adolescents who completed the HIIT arm, better baseline cardiorespiratory fitness was associated with lower post-intervention systolic blood pressure. In boys, body fat mass and fat mass index statistically mediated that relationship; in girls, the relationship appeared independent of fatness. The study does not test HIIT versus control effects directly.
Methodology
- Non-hypertensive adolescents who participated in the HIIT intervention arm.
- 64 participants.
- Bodyweight Tabata-style exercises during PE lessons.
- Work intervals: 20 seconds.
- Recovery: 10 seconds.
- Intensity: 75-80% HRmax, 145-157 bpm based on Tanaka formula for age 16.
- 10-minute warm-up plus 14-minute HIIT block.
- 1 session per week.
- 10 weeks.
- Prospective mediation analysis of the experimental HIIT arm from a school-based intervention project.
- Post-intervention blood pressure, Baseline cardiorespiratory fitness, and Fatness mediators were tracked.
Outcomes
CRF and SBP
Higher baseline CRF was associated with lower post-intervention systolic blood pressure in both sexes.
Boys B = -0.603, p = 0.010; girls B = -0.394, p = 0.037.
CRF and DBP
Baseline CRF was not significantly associated with post-intervention diastolic blood pressure.
Boys B = -0.055, p = 0.829; girls B = -0.184, p = 0.373.
Fatness mediation
Body fat mass and fat mass index mediated the CRF-SBP relationship in boys but not girls; BMI did not mediate in either sex.
Boys BFM paths: CRF→BFM p = 0.009, BFM→SBP p = 0.009, direct CRF→SBP p = 0.076. Boys FMI paths: CRF→FMI p = 0.029, FMI→SBP p = 0.007, direct p = 0.057.
Sex moderation
Sex moderated mediation models, so analyses were conducted separately for boys and girls.
Moderation interactions were identified in nearly each model except BFM as mediator for DBP.
Insights
- Baseline fitness and fatness may influence adolescent blood pressure response after HIIT.
- BMI may be less sensitive than body fat mass or fat mass index for explaining adolescent BP relationships.
- This is explanatory mediation evidence and should not be used as a direct HIIT efficacy estimate.
Limitations
- Small sample.
- No control group in this analysis.
- Only 16-year-old adolescents from one school project.
- Not nationally representative of Polish youth.
- Lifestyle covariates such as nutrition, smoking, and physical activity were not included.
- CRF was estimated using a field test rather than VO2max.
Safety
- This analysis did not report new adverse events.
- The parent HIIT project used safe school-based intensity and excluded adolescents with hypertension for this mediation analysis.
- The paper states the effort intensity was safe to avoid side effects such as dizziness or faintness.