# Short-Term High-Intensity Interval Exercise Promotes Motor Cortex Plasticity and Executive Function in Sedentary Females

PMID: 33967719
Journal: Frontiers in human neuroscience
Published: 2021
Authors: Hu M, Zeng N, Gu Z, Zheng Y, Xu K, Xue L, Leng L, Lu X, Shen Y, Huang J

## Question

Does a short-term HIIT program alter motor cortex plasticity and executive-function-related brain activation in sedentary young women?

## Summary

Sedentary young women randomized to eight supervised cycling HIIT sessions over two weeks showed changes in motor-cortex excitability and greater prefrontal activation during a Stroop task, but their behavioral Stroop performance did not clearly improve compared with controls.

## Population

- Healthy sedentary right-handed young women.
- Sample size: 32
- Age: About 19 years
- Sex: Female
- Fitness level: Sedentary
- Health status: Healthy, with PAR-Q and TMS contraindication screening

## Methodology

- Randomized controlled trial
- 2 weeks
- Supervised laboratory exercise and neurophysiology testing
- Randomized and controlled study design.

## Protocol

- Short-term cycling HIIT.
- Modality: Stationary cycling.
- Work intervals: 2 minutes at 90% heart-rate reserve.
- Recovery: 3 minutes at 50% heart-rate reserve.
- Sets or repetitions: 4 cycles per session.
- Intensity: Alternating 90% and 50% heart-rate reserve.
- Session duration: About 24-25 minutes including 2-minute warm-up and 2-minute cooldown/relaxation.
- Frequency: 4 sessions per week.
- Program length: 2 weeks.
- Progression: No progression reported.
- Normal lifestyle control.
- Modality: No exercise intervention.
- Program length: 2 weeks.

## Outcomes

### ICF
Status: improved
Intracortical facilitation decreased in the HIIT group, interpreted by the authors as altered motor cortex plasticity.

Group-by-training interaction p=0.054; HIIT pre-post t=2.76, p=0.015, d=0.690.

### SICI
Status: no clear change
Short-interval intracortical inhibition did not significantly change.

No significant group, training, or interaction effect.

### Stroop behavior
Status: no clear change
Behavioral Stroop task performance did not show a clear HIIT-specific improvement.

Reaction-time training effects were present, but group-by-training interactions were not significant.

### Prefrontal activation
Status: improved
HIIT increased activation in left dorsolateral prefrontal and orbitofrontal regions during the Stroop task.

Reported as increased oxygenated hemoglobin activation in left DLPFC and left OFC after HIIT.

## Practical Insights

- A short two-week cycling HIIT block can be feasible in sedentary young women under supervision.
- Neural activation changes should not be translated into claims of improved executive performance because behavioral outcomes were not clearly improved.
- Heart-rate reserve targets make this protocol more reproducible than all-out sprint formats.

## Limitations

- Small sample.
- Only sedentary young women were studied.
- Menstrual cycle was not monitored.
- Cortical plasticity was measured in a hand muscle while the intervention trained the lower body.
- Short intervention duration and surrogate neurophysiological outcomes.

## Safety And Adherence

- Participants were screened with PAR-Q and TMS contraindication criteria.
- No adverse events were reported in the extracted text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33967719/) (pubmed)
- [DOI](https://doi.org/10.3389/fnhum.2021.620958) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8102987/) (full text)

## Agent Guidance

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