# Effects of aquatic high-intensity interval training on aerobic capacity in adults with rheumatic and musculoskeletal diseases: the AquaHigh randomised controlled trial

PMID: 40132852
Journal: BMJ open
Published: 2025 Mar 24
Authors: Bunæs-Næss H, Heywood SE, Kvæl LAH, Heiberg KE, Nilsson BB

## Question

Does 12 weeks of aquatic high-intensity interval training improve aerobic capacity more than aquatic moderate-intensity continuous training in adults with rheumatic and musculoskeletal diseases?

## Summary

In adults with rheumatic and musculoskeletal diseases, 12 weeks of peer-led aquatic HIIT improved estimated VO2peak more than moderate aquatic exercise at 3 months, but the advantage was not maintained at 6 months. Lower-limb sit-to-stand performance improved similarly in both groups, and no exercise adverse events were reported.

## Population

- Adults with rheumatic and musculoskeletal diseases
- Sample size: 89
- Age: Mean 62 years, SD 13
- Sex: 91% female
- Fitness level: Community clinical sample with low age-relative VO2peak
- Health status: Rheumatic and musculoskeletal diseases; contraindications to high-intensity exercise excluded

## Methodology

- Assessor-blinded pragmatic multisite randomized controlled trial
- 12-week intervention with 6-month follow-up
- Community aquatic exercise groups at five local pool facilities in Eastern Norway
- Randomized and controlled study design.

## Protocol

- AHIIT.
- Modality: Aquatic exercise.
- Work intervals: 4 min at Borg RPE 14-18.
- Recovery: 2-3 min light aquatic recovery exercises.
- Sets or repetitions: 4 intervals.
- Intensity: Borg 14-18; mean achieved RPE 15.
- Session duration: 45-60 min.
- Frequency: 2 sessions/week.
- Program length: 12 weeks.
- Progression: No detailed progression reported.
- AMICT.
- Modality: Aquatic exercise.
- Work intervals: Continuous moderate aquatic exercise.
- Sets or repetitions: Continuous session after warm-up.
- Intensity: Borg RPE 12-13; mean achieved RPE 13.
- Session duration: 45-60 min.
- Frequency: 2 sessions/week.
- Program length: 12 weeks.
- Progression: Usual aquatic group format alternating flexibility, endurance, strength, and balance.

## Outcomes

### VO2peak
Status: improved
AHIIT improved estimated VO2peak more than AMICT after 12 weeks.

Mean difference 1.91 mL/kg/min, 95% CI 0.05 to 3.77, p=0.045.

### VO2peak follow-up
Status: no clear change
The between-group VO2peak advantage was not maintained at 6 months.

Mean difference 1.06 mL/kg/min, 95% CI -1.05 to 3.17, p=0.322.

### Sit-to-stand
Status: no clear change
Lower-limb functional strength improved in both groups without between-group differences.

30sSTS mean difference 0.55 at 3 months, p=0.528; 0.55 at 6 months, p=0.543.

### Safety
Status: no clear change
No exercise adverse events were reported.

## Practical Insights

- Aquatic HIIT can use a 4 x 4-min RPE-based structure for screened clinical adults.
- Intensity adherence may need repeated RPE training and instructor feedback.
- Ongoing participation may be needed to sustain aerobic gains.

## Limitations

- High dropout
- Small sample
- Participants and instructors not blinded
- No healthcare professional supervision at every session
- Pool-based protocol limits direct app translation

## Safety And Adherence

- No adverse events were reported during the intervention.
- Medical contraindications to high-intensity exercise were excluded.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/40132852/) (pubmed)
- [DOI](https://doi.org/10.1136/bmjopen-2024-090612) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11934390/) (full text)

## Agent Guidance

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