# Effects of low-volume functional and running high-intensity interval training on physical fitness in young adults with overweight/obesity

PMID: 38357496
Journal: Frontiers in Physiology
Published: 2024 Jan 31
Authors: Cao M, Yang B, Tang Y, Wang C, Yin L

## Question

How do low-volume functional HIIT and running HIIT compare with control for body composition, muscular fitness, and cardiorespiratory fitness in young adults with overweight or obesity?

## Summary

In young adults with overweight or obesity, 12 weeks of low-volume HIIT improved body composition and fitness compared with control. Functional bodyweight HIIT and treadmill running HIIT both improved cardiorespiratory fitness, while functional HIIT better preserved or increased lean mass and improved muscular fitness. Attendance was high in both HIIT arms.

## Population

- Young adults with overweight or obesity randomized to functional HIIT, running HIIT, or control.
- Sample size: 38
- Age: Eligible age 18-30 years.
- Sex: Randomized sample included 23 males and 22 females.
- Fitness level: No structured exercise training in the previous 6 months.
- Health status: Overweight or obese; no exercise-limiting conditions.

## Methodology

- Three-arm randomized controlled trial comparing functional HIIT, running HIIT, and non-training control.
- 12-week intervention with baseline and post-intervention testing.
- University-based supervised training in Shenzhen, China.
- Randomized and controlled study design.

## Protocol

- Low-volume functional HIIT.
- Modality: Bodyweight functional exercises.
- Work intervals: 30 s all-out exercise.
- Recovery: 30 s rest after each exercise; 1 min rest between sets.
- Sets or repetitions: 4 sets of 4 exercises.
- Intensity: All-out bouts with heart-rate monitoring.
- Session duration: About 25 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Exercises progressed across weeks 1-4, 5-8, and 9-12.
- Low-volume running HIIT and non-training control.
- Modality: Treadmill running HIIT; control maintained usual lifestyle.
- Work intervals: 30 s running intervals.
- Recovery: 30 s recovery at 50% MAS; 1 min rest between sets.
- Sets or repetitions: 4 sets of 4 running intervals.
- Intensity: 100% MAS weeks 1-4, 110% weeks 5-8, 120% weeks 9-12.
- Session duration: About 25 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Running intensity progressed every 4 weeks.

## Outcomes

### Body composition
Status: improved
Both HIIT modalities reduced weight, body fat percentage, and visceral fat area; functional HIIT increased lean mass while running HIIT decreased lean mass.

Functional vs running lean-mass change about +1.623 vs -1.034 kg, p<0.001.

### Muscular fitness
Status: improved
Both HIIT arms improved muscular fitness, with functional HIIT showing larger push-up and back-strength gains than running HIIT.

Push-up change HIIT-F vs HIIT-R p<0.001; back-strength change p<0.01.

### Cardiorespiratory fitness
Status: improved
Both functional and running HIIT improved estimated VO2max and shuttle-run performance, with no meaningful VO2max difference between modalities.

VO2max changes about +2.885 vs +2.192 mL/kg/min for HIIT-F vs HIIT-R; p=0.792.

### Attendance
Status: improved
Attendance was high in both HIIT arms.

HIIT-F 96.4%; HIIT-R 93.3%.

## Practical Insights

- A simple 4 x 4 structure of 30 s all-out bodyweight work can be translated into app programming.
- Functional HIIT may be a better default than running HIIT when preserving lean mass and improving muscular endurance are goals.
- High attendance in supervised settings does not guarantee the same adherence in unsupervised app use.

## Limitations

- Small sample.
- Young adults only.
- Cardiorespiratory and muscular outcomes relied on field tests.
- No accelerometer or diary for daily physical activity.
- Supervised setting limits unsupervised translation.

## Safety And Adherence

- Sessions were supervised and heart rate was monitored continuously.
- No major adverse event signal was highlighted in the extracted NXML.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/38357496/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2024.1325403) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10864534/) (full text)

## Agent Guidance

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