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ExerciseNov 14, 2023

Physio Heidi Bunaes-Naess led study on benefits of HIIT in water

Aquatic high-intensity interval training AHIIT) improves exercise capacity in adults with chronic conditions and has a similar impact as land-based training (LBHIIT), an article published today (15 November) the open access journal BMJ Open Sport & Exercise Medicine suggests.

The paper’s first author is physiotherapist Heidi Bunæs-Næss, from the Department of Rehabilitation Science and Health Technology, Faculty of Health Science in Oslo, Norway. She and her colleagues note that AHIIT may provide a safe and valuable alternative for people with chronic conditions who are unable to perform LBHIIT.

To investigate the effect of AHIIT, they analysed 18 trials that compared how AHIIT improved participants’ exercise capacity (measured by oxygen consumption, walking tests and physical fitness tests) with LBHIIT, moderate-intensity exercise in water (AMICT) or a non-exercising control group.

The trials were of varying quality, but the researchers were able to assess the certainty of evidence using the recognised GRADE system.

Photo Credit: Shutterstock
Aquatic HIIT offers exercise options for people who can't perform land based movements


Fewer adverse events reported in AHIIT 

A total of 868 participants (74 per cent of whom were women) were included. Their conditions included back pain, arthritis, chronic lung disease, type 2 diabetes and multiple sclerosis. Some participants had more than one chronic condition.

Differences between groups were expressed as standardised mean differences (SMD). Generally, an SMD of 0.2-0.5 indicates a small effect, 0.5-0.8 a moderate effect, and 0.8 or more a large effect.

The results show that AHIIT moderately improved participants’ exercise capacity compared with no exercise (SMD 0.78) and had a small beneficial effect compared with AMICT (SMD 0.45), but no difference in exercise capacity was seen for AHIIT compared with LBHIIT.

There were fewer adverse events reported in AHIIT than with LBHIIT, and adherence rates for AHIIT ranged from 84 to 100 per cent.

AHIIT may be as beneficial as LBHIIT, which gives people with chronic conditions another choice for effective HIIT or potentially a more successful environment to start and continue with high-intensity training [Heidi Bunæs-Næss et al]

Caveats and conclusions

The study was observational in nature, and the researchers acknowledge that some of the trials did not include a blind assessor, which may have affected results, and none of the studies looked at long term improvements on exercise capacity or quality of life. 

However, the detailed search strategy and inclusion of several chronic conditions, adverse events and adherence enabled a greater depth of understanding of AHIIT in a variety of populations.

‘A key finding of this meta-analysis indicates that AHIIT may be as beneficial as LBHIIT, which gives people with chronic conditions another choice for effective HIIT or potentially a more successful environment to start and continue with high-intensity training,’ Ms Bunæs-Næss and her colleagues state. They add that the natural support and buoyancy of water ‘may facilitate this effectiveness’.

They add that future research should focus on the link between exercise capacity and key patient-related outcomes, barriers to HIIT and the ongoing independent commitment to exercise.

Fact file

HIIT is a type of interval training exercise that involves brief bursts of high intensity movements followed by short recovery periods of lower intensity movements.

HIIT is considered to have more health benefits than moderate-intensity exercise for people with and without chronic conditions. It increases aerobic capacity and endurance while being time efficient, making it an attractive exercise option.

Exercising in water can also help to relieve pressure on joints, allowing people to complete movements they cannot do on land, but there is conflicting evidence on its physiological benefits.

To access the full version of the article – titledAquatic high-intensity interval training (HIIT) may be similarly effective to land based HIIT in improving exercise capacity in people with chronic conditions: a systematic review and meta-analysis doi:10.1136/bmjsem-2023-001639 – click

Author: I A McMillan
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