# High-Intensity Interval Training Improves Cardiovascular Fitness and Induces Left-Ventricular Hypertrophy During Off-Season

PMID: 40700207
Journal: Journal of Functional Morphology and Kinesiology
Published: 2025-07-16
Authors: Venckunas T, Gumauskiene B, Muanjai P, Cadefau JA, Kamandulis S

## Question

Does a 7-week off-season running HIIT program improve fitness, performance, and cardiac morphology in young amateur dinghy sailors?

## Summary

In eight young amateur sailors, 7 weeks of supervised running HIIT during the off-season improved VO2peak and running performance and increased some cardiac wall-thickness measures. The study was small and uncontrolled, so the cardiac findings should be treated as preliminary athletic adaptation evidence.

## Population

- Young amateur dinghy sailors
- Sample size: 8
- Age: 18.2 +/- 1.0 years
- Sex: 6 male and 2 female
- Fitness level: Amateur athletes
- Health status: Apparently healthy

## Methodology

- Single-arm longitudinal intervention study
- 7 weeks
- Supervised indoor-track running sessions during off-season

## Protocol

- Running HIIT.
- Modality: Indoor-track running.
- Work intervals: 200 to 1000 m repeats.
- Recovery: Sitting or slow walking recovery.
- Sets or repetitions: Progressed across 21 sessions.
- Intensity: 95-145% of 2000 m velocity depending on distance.
- Session duration: 36 to 106 min depending on week.
- Frequency: 3 sessions/week.
- Program length: 7 weeks.
- Progression: Weekly progression in interval number and distance.

## Outcomes

### VO2peak
Status: improved
VO2peak increased after 7 weeks of running HIIT.

44.1 +/- 7.2 to 46.2 +/- 8.3 mL/kg/min, p=0.02.

### Performance
Status: improved
Running performance improved in the 200 m and 2000 m tests.

Exact values were reported in the article tables; both performance tests improved.

### Cardiac structure
Status: mixed
Left atrial diameter and LV wall-thickness measures increased, while ejection fraction stayed normal and unchanged.

LA diameter 32.0 to 33.5 mm, p=0.01; LV posterior wall 7.5 to 8.2 mm, p=0.01; septum 7.6 to 8.6 mm, p=0.02.

## Practical Insights

- Performance-based pacing can scale running intervals for athletes.
- High adherence may reflect supervised team-like athlete context.
- Cardiac adaptation claims require controlled replication.

## Limitations

- Small sample
- No control group
- Athlete-only population
- Only two female participants
- Short duration
- Cycle test used after running training

## Safety And Adherence

- No adverse events or injuries were reported.
- No detailed adverse-event monitoring method was described.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/40700207/) (pubmed)
- [DOI](https://doi.org/10.3390/jfmk10030271) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12286167/) (full text)

## Agent Guidance

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