# Effects of aquatic and land high intensity interval training on hemodynamics and vascular function of middle-aged men

PMID: 39072213
Journal: Frontiers in Physiology
Published: 2024
Authors: Xin C, Fu J, Zhou Z, Zhou Y, He H

## Question

How do 8 weeks of aquatic versus land-based HIIT affect hemodynamics and vascular function in low-activity middle-aged men?

## Summary

This randomized 8-week trial compared aquatic HIIT with land-based running HIIT in low-activity middle-aged men. Both groups improved body composition, cardiac function, blood pressure, blood-flow measures, flow-mediated dilation, and pulse wave velocity, with several larger changes in the aquatic group. The study supports supervised interval running as a vascular-health intervention in this narrow population, but it did not include a non-exercise control group.

## Population

- Thirty low-activity middle-aged men were randomized to aquatic or land HIIT; final analysed sample was 27 after attendance exclusions.
- Sample size: 30
- Age: Aquatic 52.43 +/- 4.11 years; land 52.74 +/- 5.62 years
- Sex: Men only
- Fitness level: Low physical activity by IPAQ.
- Health status: No cardiovascular disease or other diseases affecting exercise; no recent lipid- or blood-pressure-lowering medications.

## Methodology

- Randomized two-arm intervention comparing aquatic HIIT with land HIIT across baseline, 4-week, and 8-week assessments.
- 8 weeks.
- Aquatic sessions in a 1.2 m deep swimming pool and land sessions on a professional track.
- Randomized and controlled study design.

## Protocol

- Aquatic HIIT.
- Modality: Fast running in 1.2 m deep pool water.
- Work intervals: 12 x 30-second fast-running intervals.
- Recovery: 1 minute complete rest between intervals.
- Sets or repetitions: 12 intervals.
- Intensity: 75-80% HRR in week 1, then 80-85% HRR from week 2 onward.
- Session duration: 40 minutes.
- Frequency: 3 sessions per week.
- Program length: 8 weeks.
- Progression: Intensity increased after week 1 from 75-80% HRR to 80-85% HRR.
- Land HIIT.
- Modality: Fast running on a professional track.
- Work intervals: 12 x 30-second fast-running intervals.
- Recovery: 1 minute complete rest between intervals.
- Sets or repetitions: 12 intervals.
- Intensity: 75-80% HRR in week 1, then 80-85% HRR from week 2 onward.
- Session duration: 40 minutes.
- Frequency: 3 sessions per week.
- Program length: 8 weeks.
- Progression: Intensity increased after week 1 from 75-80% HRR to 80-85% HRR.

## Outcomes

### Body composition
Status: improved
Both groups reduced weight, BMI, and body-fat percentage after 8 weeks; aquatic HIIT produced a larger body-fat improvement.

Aquatic p < 0.01 and land p < 0.05 for within-group changes; body-fat improvement aquatic greater than land p < 0.05.

### Cardiac function
Status: improved
SV, EDV, CO, and FS increased while HR and ESV decreased in both groups, with larger aquatic improvements.

Aquatic p < 0.01 and land p < 0.05; aquatic better than land for SV, HR, EDV, ESV, CO, and FS p < 0.05.

### Hemodynamics
Status: improved
SBP and DBP decreased while WSS and PSV increased in both groups; aquatic training showed larger improvements for SBP, WSS, and PSV.

Aquatic p < 0.01 and land p < 0.05; interactions included SBP p = 0.035, DBP p = 0.041, WSS p = 0.033, PSV p = 0.029.

### Vascular function
Status: improved
Basal diameter and FMD increased and PWV decreased in both groups; aquatic HIIT showed a larger FMD improvement.

Both groups p < 0.05 after 8 weeks; interactions: basal diameter p = 0.043, FMD p = 0.025, PWV p = 0.045.

## Practical Insights

- A land-running version of the protocol is directly programmable as 12 x 30-second fast intervals with 1-minute rests.
- Aquatic HIIT may be useful as a lower-impact or pool-based variation, but it requires supervision and pool access.
- Claims should stay focused on surrogate vascular and hemodynamic measures, not clinical cardiovascular events.

## Limitations

- Small sample.
- Men only.
- No non-exercise control group.
- Attendance-based exclusions may overstate real-world adherence.
- Eight weeks may be too short to fully compare some vascular outcomes such as PWV.

## Safety And Adherence

- No explicit adverse events were reported in the article text read.
- Participants with cardiovascular disease or other exercise-limiting diseases were excluded.
- Exercise intensity was monitored with Polar Team 2 heart-rate monitors.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/39072213/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2024.1411277) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11272582/) (full text)

## Agent Guidance

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