# Functional High-Intensity Interval Training Lowers Body Mass and Improves Coordination, Strength, Muscular Endurance, and Aerobic Endurance of Inmates in a German Prison

PMID: 34658918
Journal: Frontiers in Physiology
Published: 2021
Authors: Dransmann M, Koddebusch M, Gröben B, Wicker P

## Question

Can a short functional HIIT program improve body composition and fitness in male prison inmates?

## Summary

A 6-week supervised functional HIIT program in a German prison was associated with lower body mass and better coordination, strength, muscular endurance, and aerobic endurance among the 11 men included in final analysis. Because there was no control group, a small final sample, and a highly specific prison context, the findings are best treated as feasibility evidence.

## Population

- Male inmates in an open German prison; final analysis n=11.
- Sample size: 11
- Age: 25.82 +/- 5.25 years
- Sex: Male
- Fitness level: No other training during study; baseline BMI high on average
- Health status: Prison population with mean BMI in obesity range

## Methodology

- Single-arm pre-post intervention
- 6 weeks
- Outdoor sports field in an open German prison

## Protocol

- Functional HIIT.
- Modality: Bodyweight exercise and running.
- Work intervals: Varied; examples include 20-60 s work and 4-min running intervals.
- Recovery: Varied by session.
- Sets or repetitions: 18 varied sessions with multiple exercises and sets.
- Intensity: All-out target; average 77.95 +/- 5.58% HRmax.
- Session duration: About 40 min including warm-up.
- Frequency: 3 sessions/week.
- Program length: 6 weeks.
- Progression: Work/rest formats and exercises varied across sessions.

## Outcomes

### Body mass
Status: improved
Body mass and BMI decreased after 6 weeks.

Body mass p=0.007; BMI p=0.006.

### Coordination
Status: improved
Lateral jumps improved from 41.82 to 48.00.

p=0.024.

### Muscular endurance
Status: improved
Push-ups and sit-ups improved.

Both p<0.001.

### Aerobic endurance
Status: improved
VIFT and estimated VO2max improved.

Both p<0.001.

### Sprint
Status: no clear change
20-m sprint time did not change.

p=0.736.

## Practical Insights

- Varied bodyweight HIIT can be delivered with minimal equipment in constrained settings.
- Group supervision and participant-selected music may help adherence.
- Because there was no control group, this should not be used as strong efficacy proof.

## Limitations

- No control group
- Small final sample
- Special prison population
- Diet not tracked
- Possible drug-use confounding
- Field-test learning effects

## Safety And Adherence

- Two participants dropped out for medical reasons, but the article did not provide detailed adverse-event attribution.
- No physician clearance was performed.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/34658918/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2021.733774) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8514723/) (full text)

## Agent Guidance

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