# No changes in corticospinal excitability, biochemical markers, and working memory after six weeks of high-intensity interval training in sedentary males

PMID: 31175708
Journal: Physiological Reports
Published: 2019 Jun
Authors: Nicolini C, Toepp S, Harasym D, Michalski B, Fahnestock M, Gibala MJ, Nelson AJ

## Question

Does a 6-week 5-by-1-minute cycling HIIT program improve cardiorespiratory fitness and produce parallel changes in corticospinal excitability, intracortical circuits, serum BDNF/IGF-1/cathepsin B, or working memory in sedentary young men?

## Summary

In healthy sedentary young men, six weeks of supervised low-volume cycling HIIT improved VO2peak by about 12%, but did not improve working memory or most measured neurophysiology and blood biomarkers.

## Population

- Healthy sedentary young men.
- Sample size: 18
- Age: 23.1 +/- 3.5 years
- Sex: Male
- Fitness level: Sedentary
- Health status: Healthy

## Methodology

- Single-arm pre-post exercise intervention
- 6 weeks
- Supervised laboratory cycling sessions

## Protocol

- 5-by-1-minute cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: 1 min at about 105-135% Wpeak.
- Recovery: 1.5 min active recovery at 30% Wpeak.
- Sets or repetitions: 5.
- Intensity: Individualized Wpeak-derived workload.
- Session duration: 17.5 min.
- Frequency: 3 sessions/week.
- Program length: 6 weeks.
- Progression: Increase or decrease target workload by 10% Wpeak based on interval completion.
- Pre-training baseline.

## Outcomes

### VO2peak
Status: improved
VO2peak increased by about 12%, with all participants improving.

Significant increase; individual gains about 3% to 29%.

### Neural measures
Status: mixed
ICF decreased, but corticospinal excitability and SICI did not change.

ICF significant; MEP AUCs and SICI not significant.

### Biomarkers
Status: no clear change
BDNF, IGF-1, total CTSB, and pro-CTSB did not significantly change.

No significant pre-post changes.

### Working memory
Status: no clear change
Operation span performance was unaltered.

No significant pre-post change.

## Practical Insights

- A 17.5 min cycling HIIT protocol can improve aerobic fitness in sedentary young men over 6 weeks.
- Do not translate this study into claims about working memory or BDNF improvement.
- Completion-based intensity adjustment is a practical way to individualize hard intervals.

## Limitations

- No control group
- Small male-only sample
- Young healthy participants only
- No long-term follow-up
- Biomarker and TMS outcomes are mechanistic rather than direct health outcomes

## Safety And Adherence

- No adverse events were reported.
- All HIIT sessions were supervised and the protocol allowed workload reductions if participants could not complete an interval.
- All participants successfully completed the experiment; detailed attendance percentages were not reported.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/31175708/) (pubmed)
- [DOI](https://doi.org/10.14814/phy2.14140) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6555846/) (full text)

## Agent Guidance

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