# Acute effects of two different work-to-rest ratio of high-intensity interval training on BDNF in untrained young men

PMID: 36160866
Journal: Frontiers in Physiology
Published: 2022-09-07
Authors: Zhao K, Hu Z, Wang T, Tian L, Wang M, Liu R, Zuo C, Jihua W

## Question

Do two acute cycling HIIT protocols with different work-to-rest ratios produce different serum BDNF responses in untrained young men?

## Summary

In untrained young men, two acute cycling HIIT sessions raised serum BDNF immediately after exercise and returned to baseline by 30 minutes. The 2-min work, 1-min recovery format produced higher lactate and cortisol responses than the 1-min work, 1-min recovery format, but BDNF responses were similar.

## Population

- Healthy untrained young men
- Sample size: 12
- Age: 23.7 +/- 1.8 years
- Sex: Male
- Fitness level: Untrained for aerobic exercise
- Health status: Healthy college students

## Methodology

- Randomized crossover acute exercise study
- Two acute exercise visits separated by at least 7 days
- University exercise laboratory
- Randomized and controlled study design.

## Protocol

- HIIT2.
- Modality: Cycle ergometer.
- Work intervals: 2 min at 85-90% VO2max.
- Recovery: 1 min active recovery at 50-60% VO2max.
- Sets or repetitions: 10.
- Intensity: 85-90% VO2max.
- Session duration: About 35 min including warm-up.
- Frequency: Single acute condition.
- Program length: One session.
- Progression: None.
- HIIT1.
- Modality: Cycle ergometer.
- Work intervals: 1 min at 85-90% VO2max.
- Recovery: 1 min active recovery at 50-60% VO2max.
- Sets or repetitions: 15.
- Intensity: 85-90% VO2max.
- Session duration: About 35 min including warm-up.
- Frequency: Single acute condition.
- Program length: One session.
- Progression: None.

## Outcomes

### BDNF
Status: improved
Both HIIT protocols increased BDNF immediately after exercise, with return to baseline by 30 minutes.

Time effect p=0.001; group p=0.164; time x group p=0.755.

### Lactate
Status: mixed
Lactate increased after both protocols and was higher after the 2:1 protocol.

Group p=0.009; time x group p=0.017.

### Cortisol
Status: mixed
Cortisol rose after both protocols and remained higher at 30 minutes after the 2:1 protocol.

Time p=0.001; group p=0.034; interaction p=0.013.

## Practical Insights

- Work-rest ratio can change lactate and cortisol load even when BDNF response is similar.
- Short lab cycling HIIT reached very high RPE in untrained men.
- BDNF evidence here is acute and transient.

## Limitations

- Small sample
- Male-only participants
- Acute biomarker design
- No long-term cognitive or training outcomes
- Laboratory cycling limits app translation

## Safety And Adherence

- No adverse-event results were reported.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/36160866/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2022.988773) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9490303/) (full text)

## Agent Guidance

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