# Impact of 8 Weeks of Moderate- Versus High-Intensity Interval Training on Sleep Quality

PMID: 41752284
Journal: International journal of environmental research and public health
Published: 2026 Feb 4
Authors: Bourgeois J, Domange C, Celie B

## Question

Do 8 weeks of HIIT and MICT differ in their effects on sleep quality and cardiorespiratory fitness?

## Summary

Adults assigned to 8 weeks of running-based HIIT or moderate continuous training improved PSQI sleep-quality scores and cardiorespiratory fitness, but HIIT was not better than MICT. Both groups improved VO2max and lactate-threshold measures, while BMI and blood pressure did not change. Sleep outcomes were subjective, the sample was small, and seven participants were lost or excluded before final analysis.

## Population

- Healthy adults aged 18-45 without sleep-disrupting obligations.
- Sample size: 25
- Age: 23 +/- 2 years.
- Sex: 16 men and 9 women.
- Fitness level: Amateur athlete or sedentary/beginner; high-level athletes excluded.
- Health status: BMI 18-30; no chronic disease preventing physical activity.

## Methodology

- Randomized two-arm exercise intervention comparing HIIT and MICT.
- 8-week training intervention within a 12-week study period including baseline and post/retention sleep assessments.
- Exercise testing and monitored training using My Coach Box platform and Polar wearable monitoring.
- Randomized and controlled study design.

## Protocol

- Running HIIT.
- Modality: Running.
- Work intervals: 4 min at 90-95% HRmax.
- Recovery: 3 min at 50-70% HRmax.
- Sets or repetitions: 4 cycles.
- Intensity: Heart-rate-zone prescribed from CPET/lactate threshold.
- Session duration: About 38 min.
- Frequency: 2 sessions/week for weeks 1-2; then 2 HIIT sessions plus 1 MICT session/week for weeks 3-8.
- Program length: 8 weeks.
- Progression: Frequency increased after the first two weeks.
- MICT.
- Modality: Running.
- Sets or repetitions: Continuous 37-min effort.
- Intensity: 37 min at 80-85% HRmax after warm-up.
- Session duration: 47 min.
- Frequency: 2 sessions/week for weeks 1-2, then 3 sessions/week for weeks 3-8.
- Program length: 8 weeks.
- Progression: Frequency increased after the first two weeks.

## Outcomes

### PSQI sleep quality
Status: improved
Sleep quality improved over time regardless of training modality.

Time effect p=0.013, eta2=0.171; no modality difference p=0.809.

### Daily perceived sleep quality
Status: unclear
Daily app-reported sleep quality trended toward improvement but was not significant.

p=0.063; no modality difference p=0.544.

### VO2max
Status: improved
VO2max increased over time in both exercise modalities.

p=0.009, eta2=0.283; no significant group interaction.

### BMI and blood pressure
Status: no clear change
No significant changes in BMI or blood pressure were observed.

## Practical Insights

- For sleep-quality goals, regular exercise consistency may matter more than HIIT versus MICT intensity.
- Subjective sleep benefits should be presented as modest.
- Wearable/app sleep check-ins can support monitoring but do not replace objective sleep measurement.

## Limitations

- Small sample.
- Dropout/exclusion of seven participants.
- Subjective sleep measures only.
- Eight-week duration may miss longer-term adaptations.
- No non-exercise control arm.

## Safety And Adherence

- Seven participants were not retained in final analysis due to injuries, illnesses, personal reasons, or <80% attendance.
- No detailed intervention-related adverse-event classification was reported.
- A minimum 24 h recovery interval was enforced.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41752284/) (pubmed)
- [DOI](https://doi.org/10.3390/ijerph23020202) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12940694/) (full text)

## Agent Guidance

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