# The Relative Importance of Age at Peak Height Velocity and Fat Mass Index in High-Intensity Interval Training Effect on Cardiorespiratory Fitness in Adolescents: A Randomized Controlled Trial

PMID: 36291490
Journal: Children
Published: 2022-10-13
Authors: Domaradzki J, Koźlenia D, Popowczak M

## Question

Do biological age and baseline fat mass index influence cardiorespiratory-fitness gains after a 10-week school-based HIIT intervention in adolescent boys and girls?

## Summary

In a secondary-school sample, a 10-week Tabata-style HIIT program embedded in physical education improved Harvard Step Test fitness-index changes more than control. The analysis focused on whether biological maturity and baseline fat mass explained who improved; HIIT had a positive effect, age at peak height velocity mattered especially in girls, and baseline fat mass did not mediate the effect.

## Population

- First-year secondary-school adolescents who completed a school HIIT project and were analyzed for positive CRF response.
- Sample size: 141
- Age: About 16 years; group means around 16.1-16.3 years.
- Sex: 52 boys and 89 girls.
- Fitness level: School PE students; excluded recent additional sports activity.
- Health status: General school population; exclusions included medical contraindications.

## Methodology

- Secondary analysis of a randomized school-based controlled HIIT project using path analysis.
- 10 weeks
- One secondary school in Wroclaw, Poland, during physical education lessons.
- Randomized and controlled study design.

## Protocol

- School Tabata HIIT.
- Modality: Bodyweight/calisthenic Tabata exercises.
- Work intervals: 20 seconds maximum-intensity exercise.
- Recovery: 10 seconds rest; 1 minute between 4-minute sessions.
- Sets or repetitions: Three 4-minute sessions, each with eight cycles of two exercises.
- Intensity: Maximum intensity/as many repetitions as possible; intensity verification described in prior project papers.
- Session duration: 14 minutes of HIIT within a PE lesson.
- Frequency: 1 session per week.
- Program length: 10 weeks.
- Progression: No progression reported in this article.
- Usual PE curriculum.
- Modality: Physical education lessons without the added HIIT protocol.
- Session duration: Standard PE lessons.
- Frequency: Other PE lessons continued on schedule.
- Program length: 10 weeks.

## Outcomes

### Fitness index
Status: improved
Fitness-index changes were positive in all groups but much greater in HIIT groups.

Mean delta FI: EG boys 3.01, EG girls 1.88, CG boys/girls about 0.35; EG vs CG F=10.21, p=0.002.

### HIIT path effect
Status: improved
HIIT directly and positively affected FI changes in the whole sample and in both sexes.

Whole group beta=0.246, p=0.002; boys beta=0.313, p=0.018; girls beta=0.223, p=0.026.

### Maturity
Status: mixed
Age at peak height velocity was related to FI change overall and was close to significant in girls but not boys.

Whole group APHV beta=-0.270, p=0.035; girls beta=-0.193, p=0.053; boys beta=-0.135, p=0.311.

### Fat mass mediation
Status: no clear change
Baseline fat mass index did not mediate the relationship between HIIT, biological age, sex, and FI changes.

Whole group FMI to delta FI beta=0.107, p=0.244; indirect effects p=0.532 and p=0.268.

## Practical Insights

- Brief Tabata sessions can fit a 45-minute PE lesson.
- Adolescent response to HIIT may vary by sex and maturity status.
- Baseline fat mass alone should not be used to predict CRF gains from school HIIT.

## Limitations

- Single secondary school.
- Sex distribution and experimental/control group sizes were uneven.
- No continuous heart-rate monitoring.
- No monitoring of daily activity or nutrition.
- CRF was estimated with Harvard Step Test fitness index rather than direct VO2max.
- Adverse events and adherence were not reported.

## Safety And Adherence

- Students with medical contraindications were excluded.
- Heart rate was not continuously monitored during intervention.
- The article did not report adverse events or injuries.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/36291490/) (pubmed)
- [DOI](https://doi.org/10.3390/children9101554) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9600318/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.