# One session of high-intensity interval training (HIIT) every 5 days, improves muscle power but not static balance in lifelong sedentary ageing men: A randomized controlled trial

PMID: 28178145
Journal: Medicine
Published: 2017 Feb
Authors: Sculthorpe NF, Herbert P, Grace F

## Question

Does low-frequency HIIT, performed once every 5 days after a conditioning phase, improve peak muscle power, body composition, and static balance in lifelong sedentary ageing men?

## Summary

This randomized controlled trial tested a low-frequency cycling HIIT program in sedentary men aged 56-65 years. After a 6-week supervised conditioning phase, the intervention group performed one HIIT session every 5 days for 6 weeks, while controls stayed inactive. The low-frequency HIIT phase improved peak cycling power and lean mass and reduced body fat, but it did not improve static balance; no participants were lost to follow-up and no adverse events were recorded.

## Population

- Thirty-three lifelong sedentary but otherwise healthy men aged 56-65 years, randomized to intervention or inactive control.
- Sample size: 33
- Age: Intervention 62.3 +/- 4.1 years; control 61.6 +/- 5.0 years
- Sex: Male only
- Fitness level: No formal exercise training for at least 30 years.
- Health status: Otherwise healthy after GP approval and screening; cardiovascular and respiratory disorders excluded.

## Methodology

- Randomized controlled trial with 2:1 allocation to intervention or inactive control and three measurement phases.
- 6-week conditioning block followed by 6-week low-frequency HIIT block; controls inactive throughout.
- Exercise physiology laboratory and supervised exercise training.
- Randomized and controlled study design.

## Protocol

- Low-frequency cycling HIIT.
- Modality: Wattbike cycle ergometer.
- Work intervals: 6 x 30-second sprints.
- Recovery: 3-minute active recovery between sprints.
- Sets or repetitions: 6 sprints per session.
- Intensity: First 3 sessions at 40% PPO, final 6 at 50% PPO.
- Session duration: 5-minute warm-up plus intervals and recoveries; full duration about 23 minutes before any cool-down.
- Frequency: Once every 5 days.
- Program length: 6 weeks HIIT after 6 weeks conditioning.
- Progression: 3 familiarization sessions at 40% PPO, then 6 sessions at 50% PPO.
- Inactive control.
- Modality: No exercise intervention.
- Program length: 12-week study duration.

## Outcomes

### Peak power output
Status: improved
Low-frequency HIIT significantly increased absolute and relative peak power output in the intervention group.

Interaction p < 0.01; phase C 831.1 +/- 170.6 W intervention vs 657.3 +/- 133.1 W control.

### Body composition
Status: improved
Intervention showed reduced total body fat and increased lean body mass after HIIT.

Lean body mass interaction p < 0.01; total body fat decreased within intervention between phases A-B and B-C, p < 0.05.

### Static balance
Status: no clear change
No measure of static balance improved after conditioning or HIIT.

No phase, group, or interaction effects, p > 0.05.

### Safety/adherence
Status: improved
Feasibility was high with no loss to follow-up and no recorded adverse events.

100% completed phases A, B, and C.

## Practical Insights

- Older sedentary men may benefit from longer recovery between HIIT sessions.
- A conditioning phase before HIIT can be important for safety and adherence.
- Stationary cycling power work should not be assumed to improve balance.

## Limitations

- Male-only sample.
- Young-old age range only.
- Conditioning phase makes attribution less clean.
- No long-term follow-up.
- Static balance assessment may not have been challenging enough.

## Safety And Adherence

- No participants were lost to follow-up.
- No adverse events were recorded during conditioning or low-frequency HIIT.
- Medical clearance and conditioning preceded high-intensity training.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28178145/) (pubmed)
- [DOI](https://doi.org/10.1097/MD.0000000000006040) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5313002/) (full text)

## Agent Guidance

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