# Acute effect of resistive aquatic high-intensity interval training on metabolic costs in adults

PMID: 39469607
Journal: Frontiers in sports and active living
Published: 2024
Authors: Kwok MMY, Ng SSM, Ng YM, Tan GCC, Huang PP, Zhang Y, So BCL

## Question

Does adding resistive boots to aquatic HIIT change acute metabolic cost and perceived effort compared with standard aquatic HIIT?

## Summary

In 20 healthy young adults, a single aquatic HIIT session with resistance boots produced similar acute energy-expenditure and resting-metabolic effects to matched aquatic HIIT without boots. Participants were screened and supervised by an aquatic physiotherapist, and all completed the protocols.

## Population

- Twenty clinically healthy young adults
- Sample size: 20
- Age: Men 24.27 +/- 6.59 years; women 25.44 +/- 4.22 years
- Sex: 11 men, 9 women
- Fitness level: Healthy adults; physical activity assessed
- Health status: Clinically healthy

## Methodology

- Randomized crossover acute exercise study
- Single-session crossover with preliminary testing and familiarization
- Heated hydrotherapy pool in a university setting
- Randomized and controlled study design.

## Protocol

- Resistive aquatic HIIT.
- Modality: Aquatic stationary running with resistance boots.
- Work intervals: 1 minute.
- Recovery: 1 minute dynamic rest.
- Sets or repetitions: 5 intervals.
- Intensity: 90% HRmax work, 70% HRmax recovery.
- Session duration: 20 minutes including warm-up and cool-down.
- Frequency: Single acute session.
- Program length: Acute crossover.
- Progression: None.
- Aquatic HIIT.
- Modality: Aquatic stationary running without resistance boots.
- Work intervals: 1 minute.
- Recovery: 1 minute dynamic rest.
- Sets or repetitions: 5 intervals.
- Intensity: 90% HRmax work, 70% HRmax recovery.
- Session duration: 20 minutes including warm-up and cool-down.
- Frequency: Single acute session.
- Program length: Acute crossover.
- Progression: None.

## Outcomes

### REE
Status: improved
Resting energy expenditure increased after both aquatic HIIT protocols.

Time effect p<0.01; group x time p=0.76.

### RER
Status: mixed
RER decreased after exercise in both groups without a between-group difference.

Time effect p<0.05; group x time p=0.88.

### Energy
Status: no clear change
Total energy expenditure did not differ between standard and resistive aquatic HIIT.

Between-group p=0.59.

### RPE
Status: mixed
RPE increased in both conditions, with some evidence that the resistive protocol felt harder.

Time effect p<0.01; table between-group p=0.11, discussion reports p=0.007.

## Practical Insights

- A 5 x 1-minute aquatic HIIT format can raise acute metabolic measures in healthy adults.
- Adding resistance boots may increase perceived effort without clearly improving energy expenditure.
- Pool-based HIIT has safety and access constraints that differ from land-based app programming.

## Limitations

- Small sample of healthy young adults.
- Acute effects only.
- Findings may not generalize to older adults or clinical populations.
- Long-term training outcomes were not measured.

## Safety And Adherence

- Adverse events were not explicitly reported.
- Participants were screened for health status, pregnancy, hydrophobia, relevant disease, recent lower-limb injury or surgery, and contraindications to aquatic exercise.
- All 20 participants completed incremental tests and both aquatic HIIT protocols under registered aquatic physiotherapist supervision.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/39469607/) (pubmed)
- [DOI](https://doi.org/10.3389/fspor.2024.1421281) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11513309/) (full text)

## Agent Guidance

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