# Optimising adolescent health: a comparative study of high-intensity interval training and moderate-intensity continuous training on body composition and cardiovascular fitness in sedentary male youth

PMID: 41210262
Journal: Frontiers in sports and active living
Published: 2025
Authors: Yahat H

## Question

How do 8 weeks of school-based HIIT and MICT compare for body composition and cardiovascular fitness in sedentary normal-weight male adolescents?

## Summary

In sedentary male adolescents, 8 weeks of supervised running HIIT and MICT both reduced body fat, body weight, skinfold thickness, and resting heart rate compared with a no-exercise control group. HIIT achieved similar improvements with a shorter 20-minute session than the 30-minute MICT session. However, the article reports incomplete heart-rate fidelity data and a failed intensity manipulation check, so claims about the intended intensity contrast need caution.

## Population

- Sedentary male adolescents aged 16-17.
- Sample size: 60
- Age: 16.10 +/- 0.30 years.
- Sex: Male.
- Fitness level: Sedentary by IPAQ-SF low activity.
- Health status: Described as normal-weight; baseline BMI mean 25.15 +/- 1.86 kg/m2 and body fat about 25-26%.

## Methodology

- Three-arm randomized controlled trial.
- 8 weeks.
- Extracurricular school-based program in the National Sports Hall, supervised by the first researcher and school physical education staff.
- Randomized and controlled study design.

## Protocol

- School running HIIT.
- Modality: Running/walking.
- Work intervals: 30 s at 80-90% HRmax.
- Recovery: 90 s walking at about 50% HRmax.
- Sets or repetitions: 6 rounds.
- Intensity: HRR-prescribed high-intensity running.
- Session duration: 20 min including warm-up and cool-down.
- Frequency: 4 sessions/week.
- Program length: 8 weeks.
- Progression: No clear week-by-week progression reported for the trial protocol.
- MICT and control.
- Modality: Continuous running or no structured activity.
- Sets or repetitions: MICT continuous run.
- Intensity: MICT 60-70% HRmax.
- Session duration: 30 min for MICT.
- Frequency: 4 sessions/week for MICT.
- Program length: 8 weeks.

## Outcomes

### Body fat percentage
Status: improved
Body fat fell in HIIT and MICT more than control.

HIIT 26.00% to 20.00%; MICT 25.80% to 20.10%; control 25.20% to 24.20%; F(2,57)=185.97, p<0.001, eta2=0.86.

### Body weight
Status: improved
Body weight declined by about 5.75 kg in both active arms and minimally in control.

HIIT 77.15 to 71.40 kg; MICT 77.20 to 71.45 kg; control 79.10 to 78.40 kg; F(2,57)=157.06, p<0.001, eta2=0.84.

### Skinfold thickness
Status: improved
Skinfold measures decreased in both active arms more than control.

HIIT 24.90 to 18.75 mm; MICT 24.30 to 18.55 mm; control 23.05 to 22.10 mm; eta2=0.961.

### Resting heart rate
Status: improved
Resting heart rate decreased in HIIT and MICT, with no meaningful control improvement.

HIIT 78.25 to 71.10 bpm; MICT 80.05 to 74.35 bpm; control 78.45 to 78.65 bpm; eta2=0.953.

### Intensity fidelity
Status: unclear
Heart-rate manipulation check did not confirm clear separation between prescribed intensities.

Paired tests: HIIT p=0.693; MICT p=0.275.

## Practical Insights

- A 6 x 30 s running HIIT session can fit school schedules and may match longer MICT for short-term body-composition outcomes.
- Verify actual intensity with time-in-zone or RPE when making intensity-specific claims.
- Results apply best to supervised adolescent male settings.

## Limitations

- Male-only adolescent sample.
- Short duration and no follow-up.
- Indirect fitness measure using resting heart rate rather than VO2max.
- Dietary intake not quantified.
- Control physical activity not objectively monitored.
- Incomplete fidelity/adherence capture.

## Safety And Adherence

- No adverse events were observed or reported.
- No injuries requiring first aid or medical evaluation.
- No syncope, chest pain, respiratory distress, heat illness, harm-related session terminations, or harm-related withdrawals.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41210262/) (pubmed)
- [DOI](https://doi.org/10.3389/fspor.2025.1655906) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12593510/) (full text)

## Agent Guidance

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