# High-Intensity Interval Training (HIIT): Impact of Duration on Body Composition, Cardiometabolic Health, and Aerobic Capacity in Adolescent Women

PMID: 41003007
Journal: Metabolites
Published: 2025 Sep 19
Authors: Stankovic M, Čaprić I, Pezelj L, Biševac E, Mekić R, Zećirović A, Salihagić Z, Ajdinović A, Jelaska I

## Question

How do 6-week and 8-week HIIT programs affect body composition, lipid profile, blood pressure, glucose, and aerobic capacity in adolescent women aged 17-19?

## Summary

This randomized experimental study compared 6-week and 8-week running HIIT programs with a control group in healthy, normal-BMI adolescent women. Both HIIT durations improved body weight, BMI, body fat percentage, lipid markers except HDL, blood pressure, and estimated VO2max. The 8-week program had stronger effects on triglycerides and total cholesterol, while glucose and HDL did not significantly change.

## Population

- Healthy adolescent women with normal BMI.
- Sample size: 122
- Age: 17-19 years.
- Sex: Female only.
- Fitness level: Physically active at least 150 minutes per week.
- Health status: Healthy, BMI 18.5-24.9 kg/m2; excluded exercise contraindications, acute illness/injury, psychiatric/psychological disorders, heart disease, relevant surgeries/hormonal procedures, metabolism-altering medications, and absence from more than 10% of sessions.

## Methodology

- Randomized experimental pre/post study with two HIIT-duration groups and a control group.
- 6 weeks for HIIT 1 and 8 weeks for HIIT 2.
- Community/school-style training and standardized testing from April to July 2025.
- Randomized and controlled study design.

## Protocol

- 6- or 8-week running HIIT.
- Modality: Running.
- Work intervals: 30 seconds at 90-95% HRmax.
- Recovery: 30 seconds active recovery at 50-55% HRmax.
- Sets or repetitions: 2 sets x 6 intervals in weeks 1-2, 2 x 7 in weeks 3-4, 2 x 8 in weeks 5-6, and 2 x 9 in weeks 7-8 for the 8-week group; 4-minute passive recovery between sets.
- Intensity: 90-95% HRmax work, 50-55% HRmax recovery; actual mean work HR approximately 185-186 bpm and peak 192-193 bpm.
- Session duration: 15-minute warm-up plus interval block plus 15-minute cooldown.
- Frequency: 2 sessions/week.
- Program length: 6 weeks in HIIT 1 or 8 weeks in HIIT 2.
- Progression: Interval count increased every two weeks.
- No additional training control.
- Modality: No additional HIIT training.
- Program length: 6-8 weeks.

## Outcomes

### Body composition
Status: improved
Both HIIT durations reduced body mass, BMI, and body fat percentage compared with control.

All p<0.001; BMI reduction of about 1.1 kg/m2 exceeded the authors' Delphi-derived clinical threshold.

### Lipids
Status: improved
Total cholesterol, triglycerides, and LDL improved in both HIIT groups, with stronger triglyceride and total cholesterol effects in the 8-week group; HDL did not change significantly.

TC, TG, LDL all p<0.001; HDL p=0.825; HIIT 2 showed more pronounced TG and TC reduction than HIIT 1.

### Blood pressure
Status: improved
Systolic and diastolic blood pressure improved after both HIIT programs.

SBP and DBP p<0.001; reductions exceeded Delphi-derived clinical thresholds.

### Glucose
Status: no clear change
Fasting glycemia did not significantly change.

p=0.078.

### Aerobic capacity
Status: improved
VO2max increased after both 6 and 8 weeks, with no significant difference between HIIT durations.

p<0.001; authors discuss approximately 18% improvement during the 8-week intervention.

## Practical Insights

- A 30/30 running HIIT program can be progressed by adding one interval pair every two weeks.
- Six weeks may be enough for fitness and body-composition changes in healthy adolescent women, while lipid outcomes may benefit from 8 weeks.
- This protocol is most applicable to screened healthy adolescents with HR monitoring.

## Limitations

- VO2max was estimated by shuttle run rather than measured directly.
- No long-term follow-up.
- Dietary habits, sleep, menstrual cycle phase, physical activity, and socioeconomic level were not controlled.
- Population was healthy, normal-BMI adolescent women, limiting generalizability.
- Adverse-event reporting was not clear.

## Safety And Adherence

- Adverse events were not explicitly reported in the extracted full text.
- Participants with contraindications, acute injuries/illness, heart disease, or metabolism-altering medication use were excluded.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41003007/) (pubmed)
- [DOI](https://doi.org/10.3390/metabo15090623) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12472050/) (full text)

## Agent Guidance

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