# Effects of Two Workload-Matched High-Intensity Interval Training Protocols on Regional Body Composition and Fat Oxidation in Obese Men

PMID: 33801691
Journal: Nutrients
Published: 2021 Mar 27
Authors: Tsirigkakis S, Mastorakos G, Koutedakis Y, Mougios V, Nevill AM, Pafili Z, Bogdanis GC

## Question

Do workload-matched cycling HIIT protocols using 10-second versus 60-second bouts differ in effects on regional body composition and fat oxidation in obese adult men?

## Summary

Sixteen inactive men with obesity completed 8 weeks of cycling HIIT using either very short 10-second bouts or longer 60-second bouts matched for total work. Both formats improved VO2peak, fat oxidation, trunk fat, waist circumference, and leg lean mass similarly, with high attendance and no reported injuries or adverse events.

## Population

- Inactive healthy adult men with obesity or high body fat.
- Sample size: 16
- Age: 38.9 +/- 7.3 years overall; HIIT10 37.2 +/- 9.5, HIIT60 40.2 +/- 3.9
- Sex: Men only
- Fitness level: Low-to-moderate physical activity; no structured exercise in previous 12 months
- Health status: BMI 28-35 kg/m2 and fat mass >=25%; endocrine/metabolic disorders, chronic diseases, diabetes family history/early cardiac mortality, smoking, medications, supplements, and mental disorders excluded

## Methodology

- Parallel randomized training study comparing two workload-matched HIIT protocols
- 8 weeks
- Exercise physiology laboratory and university medical/radiology facilities
- Randomized and controlled study design.

## Protocol

- HIIT10 cycling.
- Modality: Cycle ergometer.
- Work intervals: 10 seconds at 100% Wpeak.
- Recovery: 15 seconds active recovery at 15% Wpeak.
- Sets or repetitions: 48 repetitions.
- Intensity: 100% Wpeak work; 15% Wpeak recovery.
- Session duration: 23 minutes including warm-up.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: Wpeak retested and workload readjusted at week 4.
- HIIT60 cycling.
- Modality: Cycle ergometer.
- Work intervals: 60 seconds at 100% Wpeak.
- Recovery: 90 seconds active recovery at 15% Wpeak.
- Sets or repetitions: 8 repetitions.
- Intensity: 100% Wpeak work; 15% Wpeak recovery.
- Session duration: 23 minutes including warm-up.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: Wpeak retested and workload readjusted at week 4.

## Outcomes

### VO2peak
Status: improved
VO2peak improved similarly in both HIIT groups.

+20.0 +/- 7.2%, p<0.001, ES=1.42.

### Body composition
Status: improved
Total and trunk fat mass decreased and leg lean mass increased similarly in both groups.

Total fat -1.81 kg, p=0.002; trunk fat -1.45 kg, p<0.001; leg lean mass +0.86 kg, p<0.001.

### Fat oxidation
Status: improved
Fat oxidation increased over a wide range of submaximal intensities and peak fat oxidation increased.

PFO 0.20 +/- 0.05 to 0.33 +/- 0.08 g/min, p=0.001; Fatpeak 33.6 +/- 4.6 to 37.6 +/- 6.7% VO2peak, p=0.039.

### Bout duration
Status: no clear change
The 10-second and 60-second protocols did not differ for the examined outcomes.

No significant group or interaction effects for main outcomes.

## Practical Insights

- When total work is matched, very short and longer cycling intervals can produce similar adaptations.
- Cycling HIIT can be a lower-impact option for inactive men with obesity.
- Readjusting intensity during a block helps maintain relative dose.

## Limitations

- No non-training control group
- Small men-only sample
- Diet was self-recorded rather than fully controlled

## Safety And Adherence

- Attendance was high in both groups.
- No physical injuries and no adverse events were reported.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33801691/) (pubmed)
- [DOI](https://doi.org/10.3390/nu13041096) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8066011/) (full text)

## Agent Guidance

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