# Cardiovascular and cardiorespiratory effects of high-intensity interval training in body fat responders and non-responders

PMID: 38918508
Journal: Scientific Reports
Published: 2024-06-25
Authors: Domaradzki J, Koźlenia D

## Question

Do adolescents who reduce body-fat percentage after school-based HIIT differ from non-responders in cardiovascular and cardiorespiratory adaptations?

## Summary

In 73 adolescents assigned to a 10-week school Tabata HIIT program, body-fat responders gained more cardiorespiratory fitness than body-fat non-responders, but systolic blood pressure improved in both groups. The analysis was based on responder subgroups from the HIIT arm and did not include a parallel control comparison.

## Population

- Adolescents from the experimental arm of a school-based HIIT intervention.
- Sample size: 73
- Age: Approximately 16 years
- Sex: 31 male and 42 female
- Fitness level: School PE participants
- Health status: Apparently healthy adolescents.

## Methodology

- Responder/non-responder subgroup analysis within the experimental arm of a school HIIT intervention.
- 10 weeks
- School physical education in Wroclaw, Poland.

## Protocol

- School Tabata HIIT.
- Modality: Bodyweight exercises.
- Work intervals: 20 seconds.
- Recovery: 10 seconds active recovery.
- Sets or repetitions: Three 4-minute Tabata sessions, 8 cycles each.
- Intensity: 75-80% HRmax; first-session mean HR 155.8 +/- 18.2 bpm.
- Session duration: 45-minute PE lesson with 14-minute HIIT block.
- Frequency: 1 session per week.
- Program length: 10 weeks.
- Progression: No explicit progression reported.

## Outcomes

### Body fat
Status: mixed
Responder classification separated participants with decreased body fat from those with increased body fat.

Responder change -2.30 +/- 3.51 percentage points; non-responder change +1.51 +/- 1.54; delta p<0.001.

### Fitness index
Status: mixed
Fitness index improved in body-fat responders but not non-responders.

Interaction F(1,71)=14.12, p<0.001; responders p<0.001, d=0.82; non-responders p=0.576, d=0.13.

### Blood pressure
Status: improved
Systolic blood pressure decreased over time in both responder categories.

SBP time effect F=38.68, p<0.001; no responder x time interaction.

### DBP
Status: mixed
DBP reporting was internally inconsistent, but the model showed a significant time effect and no responder interaction.

DBP time effect F=11.40, p=0.001; text and discussion differed on whether both groups improved.

## Practical Insights

- Do not treat body-fat non-response as overall non-response.
- Fitness and blood-pressure outcomes should be tracked separately.
- Short bodyweight HIIT can fit into a school PE lesson.

## Limitations

- Responder subgroup analysis without a concurrent control in this paper.
- Small subgroups after responder/non-responder classification.
- Responder threshold based on typical error.
- Harvard Step Test instead of VO2max.
- BIA instead of DEXA.
- Sexes were agglomerated in key analyses.

## Safety And Adherence

- No adverse events or injuries were reported in the extracted text.
- Heart-rate monitoring was used during supervised PE.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/38918508/) (pubmed)
- [DOI](https://doi.org/10.1038/s41598-024-65444-z) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11199575/) (full text)

## Agent Guidance

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