# Sex differences in the effects of 12 weeks sprint interval training on body fat mass and the rates of fatty acid oxidation and VO(2)max during exercise

PMID: 27900150
Journal: BMJ Open Sport & Exercise Medicine
Published: 2016
Authors: Bagley L, Slevin M, Bradburn S, Liu D, Murgatroyd C, Morrissey G, Carroll M, Piasecki M, Gilmore WS, McPhee JS

## Question

Do men and women respond differently to 12 weeks of very short-duration sprint interval training for body fat, fat oxidation, VO2max, and metabolic risk markers?

## Summary

A 12-week sprint interval program with only 80 seconds of hard work per session improved VO2max and fat-oxidation capacity in adults. Men lost more fat mass, while women had a larger relative VO2max improvement; fasting glucose, insulin, HOMA-IR, triglycerides, total cholesterol, and HDL did not materially change.

## Population

- General adult men and women completing 12 weeks of low-volume sprint interval cycling.
- Sample size: 41
- Age: Mean 39 +/- 2 years
- Sex: 24 men, 17 women
- Fitness level: General population, not athlete-specific
- Health status: Generally healthy; mean BMI 24.6 +/- 0.6 kg/m2

## Methodology

- Single-arm pre-post intervention with sex comparison
- 12 weeks
- University laboratory and gym-based cycling sessions

## Protocol

- Low-volume sprint interval training.
- Modality: Cycle ergometer.
- Work intervals: 20 s.
- Recovery: 2 min very low-intensity cycling.
- Sets or repetitions: 4 sprints.
- Intensity: Maximal effort at 175% of VO2max-test workload.
- Session duration: Less than 10 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Workload increased 5% every 2 weeks.

## Outcomes

### VO2max
Status: improved
VO2max increased overall, with a larger relative improvement in women.

Overall about +9%; women +18.7%, men +6.0%; sex x training p=0.009.

### Fat mass
Status: mixed
Fat mass decreased overall, with clearer loss in men than women.

Overall -1.0 kg; men lost more fat mass and percent body fat than women.

### Fat oxidation
Status: improved
FATmax improved similarly in men and women.

Approximately +13% improvement.

### Glucose markers
Status: no clear change
Fasting glucose, insulin, and HOMA-IR did not significantly change.

Glucose p=0.496; insulin p=0.708; HOMA p=0.426.

### Lipids
Status: mixed
LDL decreased and HDL:TC ratio improved, while triglycerides, total cholesterol, and HDL did not significantly change.

LDL -8%, p=0.028; HDL:TC +6%, p=0.005.

## Practical Insights

- Very low-volume sprint intervals can improve fitness with minimal hard-work time.
- Body-fat and VO2max responses may differ by sex.
- Do not overstate glucose-control improvements from this trial.

## Limitations

- No non-exercise control group
- Moderate sample size for sex comparisons
- Maximal sprint protocol
- Diet and outside exercise were not tightly controlled
- Not all sessions fully laboratory supervised

## Safety And Adherence

- No explicit adverse-event results were reported.
- Maximal sprint cycling was used, which limits direct translation to unscreened users.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/27900150/) (pubmed)
- [DOI](https://doi.org/10.1136/bmjsem-2015-000056) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5117024/) (full text)

## Agent Guidance

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