# Effect of eight-week high-intensity interval training versus moderate-intensity continuous training programme on body composition, cardiometabolic risk factors in sedentary adolescents

PMID: 39183975
Journal: Frontiers in physiology
Published: 2024
Authors: Sun F, Williams CA, Sun Q, Hu F, Zhang T

## Question

Do 8 weeks of running-based HIIT and MICT improve body composition and cardiometabolic risk factors in sedentary adolescents, and are there differences between the two programs?

## Summary

This small randomized trial tested 8 weeks of field-based running HIIT against moderate continuous running and usual activity in sedentary normal-weight Chinese university-age adolescents. HIIT and MICT similarly reduced several body-fat measures, but HIIT had additional within-group improvements in waist/hip ratio, blood pressure, and triglycerides. Insulin resistance and several lipids did not significantly improve.

## Population

- Sedentary normal-weight Chinese adolescents/university entrants with no known disease or exercise contraindications.
- Sample size: 18
- Age: 18.5 +/- 0.3 years.
- Sex: 11 females and 7 males.
- Fitness level: Inactive; more than 8 hours/day sedentary behavior, no regular physical activity during the prior 3 years, activities of daily living only.
- Health status: Healthy normal-weight youth; excluded known disease, exercise contraindications, medications/substances affecting blood pressure, cholesterol, or carbohydrate metabolism.

## Methodology

- Three-arm randomized controlled trial with HIIT, MICT, and no-intervention control groups.
- 8 weeks, with baseline and 48-hour post-trial measurements.
- Nanjing Agricultural University athletics field and clinical/laboratory testing sites in China.
- Randomized and controlled study design.

## Protocol

- Running HIIT.
- Modality: Outdoor running sprints.
- Work intervals: 8 seconds all-out in weeks 1-4; 10 seconds all-out in weeks 5-8.
- Recovery: 24 seconds active walking recovery in weeks 1-4; 30 seconds in weeks 5-8.
- Sets or repetitions: 21-24 sprint repetitions within a 20-minute interval block.
- Intensity: 85-95% HRmax; actual recorded exercise HR generally corresponded to target intensity.
- Session duration: 30 minutes including 5-minute warm-up, 20-minute sprint interval training, and 5-minute cooldown/stretching.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: Interval duration increased after week 4 from 8/24 seconds to 10/30 seconds.
- MICT and no-intervention control.
- Modality: Outdoor continuous running for MICT; usual activity for control.
- Work intervals: 20 minutes continuous running for MICT.
- Sets or repetitions: One continuous 20-minute run.
- Intensity: 65-75% HRmax for MICT.
- Session duration: 30 minutes including 5-minute warm-up, 20-minute run, and 5-minute cooldown/stretching.
- Frequency: 3 sessions/week for MICT.
- Program length: 8 weeks.

## Outcomes

### Body fat
Status: improved
HIIT and MICT both reduced body fat mass, body fat percentage, and visceral fat area; HIIT uniquely reduced waist/hip ratio.

BF: HIIT p=0.021 ES=0.19, MICT p=0.016 ES=0.30; BFP: HIIT p=0.037 ES=0.17, MICT p=0.041 ES=0.28; VFA: HIIT p=0.001 ES=0.35, MICT p=0.003 ES=0.49; WHR improved in HIIT p=0.033 ES=0.43 but not MICT.

### Blood pressure and triglycerides
Status: improved
Within-group pairwise comparisons showed systolic BP, diastolic BP, and triglycerides decreased in HIIT but not MICT or control.

SBP p=0.018 ES=0.84; DBP p=0.008 ES=1.76; TG p=0.004 ES=1.33.

### Insulin resistance and inflammation
Status: no clear change
The study did not confirm significant improvements in insulin resistance or hs-CRP, although HOMA-IR slightly decreased in HIIT and increased in MICT/control.

Authors state statistical results did not confirm an effective insulin resistance change; HIIT HOMA-IR decreased 5.63% while MICT and control increased.

### BMI and cholesterol fractions
Status: no clear change
BMI, total cholesterol, HDL-C, and LDL-C did not significantly change.

Reported as p > 0.05.

## Practical Insights

- Very short running sprints with long active recovery can improve some body-composition markers in sedentary normal-weight adolescents.
- For cardiometabolic markers, the strongest signals were blood pressure and triglycerides in the HIIT group, not broad lipid or insulin improvements.
- Heart-rate monitoring and professional supervision were part of the field protocol.

## Limitations

- Very small completed sample with only six participants per group.
- Pandemic conditions limited enrollment and protocol fidelity.
- Normal-weight late adolescents limit generalization to adults, children, or adolescents with obesity.
- No long-term follow-up and no detailed adverse-event table.
- Diet was recommended but not tightly controlled.

## Safety And Adherence

- No testing- or training-related severe injuries occurred.
- One participant was excluded before randomization for bradycardia after ECG screening.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/39183975/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2024.1450341) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11341307/) (full text)

## Agent Guidance

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