# Comparison of the Effectiveness of High-Intensity Interval Training in Hypoxia and Normoxia in Healthy Male Volunteers: A Pilot Study

PMID: 31662994
Journal: BioMed research international
Published: 2019
Authors: Żebrowska A, Jastrzębski D, Sadowska-Krępa E, Sikora M, Di Giulio C

## Question

Does the same HIIT program performed in normobaric hypoxia produce different cardiorespiratory and angiogenic responses than normoxia?

## Summary

Twelve active young men completed the same 3-week cycling interval program in normal oxygen and low-oxygen chamber conditions. Hypoxic training produced larger changes in VO2max and several angiogenic or nitric-oxide markers, but this pilot used specialized equipment and a small male sample.

## Population

- Twelve healthy physically active young men.
- Sample size: 12
- Age: 24.4 +/- 4.0 years
- Sex: Male
- Fitness level: Physically active; VO2max 54.2 +/- 2.6 ml/kg/min
- Health status: Healthy

## Methodology

- Randomized crossover pilot training study
- Two 3-week training periods separated by a 6-week washout
- Controlled normobaric hypoxia/normoxia chamber and exercise laboratory
- Randomized and controlled study design.

## Protocol

- Hypoxic HIIT.
- Modality: Cycle ergometer in normobaric hypoxia.
- Work intervals: 5 minutes.
- Recovery: 5 minutes rest after each bout.
- Sets or repetitions: 6 bouts.
- Intensity: 120% individual lactate threshold; FiO2 15.2%.
- Session duration: About 65 minutes including 15-minute acclimatization and 5-minute warm-up.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: Not reported.
- Normoxic HIIT.
- Modality: Cycle ergometer in normoxia.
- Work intervals: 5 minutes.
- Recovery: 5 minutes rest after each bout.
- Sets or repetitions: 6 bouts.
- Intensity: 120% individual lactate threshold; FiO2 20.9%.
- Session duration: About 65 minutes including acclimatization and warm-up.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: Not reported.

## Outcomes

### VO2max
Status: improved
Hypoxic HIIT increased VO2max more than normoxic HIIT.

Training x group F=15.5, p<0.001; within hypoxia p=0.01.

### HIF-1alpha and NO
Status: improved
Hypoxia increased HIF-1alpha and nitric oxide responses compared with normoxia.

HIF-1alpha and NO interactions reported around p<0.01 to p<0.05.

### Cytokines
Status: mixed
IL-1beta postexercise was higher after hypoxia, but TNF-alpha and IL-6 did not significantly change.

IL-1beta postexercise p=0.01; TNF-alpha and IL-6 p>0.05.

## Practical Insights

- Hypoxia may change biomarker response to the same interval dose, but the protocol is not practical for ordinary app users.
- A 5-minute on/5-minute off cycling structure is reproducible when threshold testing is available.

## Limitations

- Pilot sample of 12 active men.
- Short 3-week blocks.
- Hypoxia chamber limits translation.
- Dropout/noncompletion count was not reported.

## Safety And Adherence

- The article did not report adverse events.
- Participants were screened for hemodynamic dysfunction and recent inflammatory disease and trained under laboratory supervision with physiologic monitoring.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/31662994/) (pubmed)
- [DOI](https://doi.org/10.1155/2019/7315714) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6778879/) (full text)

## Agent Guidance

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