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Swimming is one high-intensity exercise people can do in the pool. AleksandarGeorgiev/Getty Images
  • Researchers report that Aquatic High Intensity Interval Training (AHIIT) improves exercise capability in adults with chronic conditions.
  • They noted AHIIT had a similar impact as land-based training (LBHIIT) and may be a safe and valuable alternative for people with chronic conditions unable to perform the land-based exercise.
  • Experts say exercising in water can help relieve pressure on joints, allowing people to complete movements they can’t necessarily do on land, but there’s conflicting evidence on its physiological benefits.

Researchers have a message for people with chronic conditions who find land-based training too difficult.

Get in. The water’s fine.

Published today in the journal BMJ Open Sport & Exercise Medicine. the study states that high-intensity interval training in water, often called aquatic HIIT (AHIIT) improves exercise capacity in adults with chronic conditions such as diabetes and arthritis.

The researchers also say that AHIIT has a similar impact as land-based training (LBHIIT) and may be a safe and valuable alternative for people with chronic conditions who are unable to perform LBHIIT.

Dr. Mark Slabaugh, a sports medicine specialist at Mercy Medical Center in Baltimore, told Medical News Today the benefits of water exercise is clear for people suffering from conditions such as tendinitis, arthritis, and chronic pain.

“This study gives us as clinicians even more options for patients who are interested in cross training and doing HIIT workouts but can not due to joint pain,” said Slabaugh, who was not involved in the study. “I counsel my patients to start out with these light AHIIT sessions and gradually work up to a longer duration of swimming, which has been proven to be a sport which can be done well into your later years.”

HIIT is an interval training exercise involving brief bursts of high intensity movements followed by short recovery periods with lower intensity movements.

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

On the other hand, researchers say that exercising in water can help relieve pressure on joints, allowing people to complete movements they can’t necessarily do on land.

There is, however, conflicting evidence on AHIIT’s physiological benefits.

The research team analyzed 18 trials, comparing how AHIIT improved participants’ exercise capability (measured by oxygen consumption, walking tests and other physical fitness tests) compared with LBHIIT.

They also compared AHIIT with moderate-intensity exercise in water (AMICT) and a non-exercising control group.

The researchers assessed the certainty of evidence using the recognized GRADE system.

They looked at 868 participants – 74% of whom were women – who had a range of conditions including back pain, arthritis, chronic lung disease (COPD), type 2 diabetes, and multiple sclerosis. Some participants had more than one chronic condition.

The study expressed differences between groups as standardized mean differences (SMD). An SMD of 0.2-0.49 indicated a small effect, 0.5-0.79 a moderate effect, and 0.8 or more a large effect.

The researchers reported 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). In addition, no difference in exercise capacity was seen for AHIIT compared with LBHIIT.

There were fewer adverse events reported in AHIIT than with LBHIIT. Adherence rates for AHIIT ranged from 84% to 100%.

“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,” the researchers said in a statement.

They added that the natural support and buoyancy of water “may facilitate this effectiveness.”

They also stressed it was an observational study and acknowledged some of the trials didn’t include a blind assessor, which may have affected results. None of the studies looked at long-term improvements on exercise capacity or quality of life.

They concluded 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.

The team said future research should examine the link between exercise capacity and key patient-related outcomes, barriers to HIIT, and the ongoing independent commitment to exercise.

Sydnee Corbin is a physical therapist and clinic director at SporTherapy in Texas, where they use a pool for therapy.

Corbin, who was not involved in the study, told Medical News Today that water-based therapy offloads joints while giving people increased resistance with which to help with conditions such as osteoarthritis, balance deficits, sensory processing disorders, and generalized weakness/deconditioning as well as with post-operative patients.

“The pool is a great opportunity to provide sensory feedback while also providing resistance, which is a unique property that is difficult to replicate on land,” Corbin said. “An aquatic environment can be a great way to reach a patient population that is otherwise sedentary or inactive.”

Corbin said people with osteoarthritis, chronic low back pain, or other chronic conditions may be limited in their tolerance to LBHIIT and not be able to fully participate and enjoy the benefits HIIT has to offer.

“We can be more inclusive to those populations and decrease further health risks to those populations by introducing AHIIT,” she said. “The aquatic environment both provides offloading of joints, but also sensory input to their system which may be otherwise sensitized from chronic pain, constant resistance from the water, and if performing in a warmed pool may provide relaxation to otherwise painful muscles and joints.”

Dr. William Ashford, an orthopedic surgeon at AICA Orthopedics in Atlanta who wasn’t involved in the study, told Medical News Today that AHIIT presents a highly effective treatment modality, particularly for people with musculoskeletal conditions such as arthritis and chronic back pain.

Ashford said buoyancy of water provides a natural resistance while minimizing joint stress, allowing people to perform exercises that would be painful or impossible on land.

“Moreover, the cardiovascular benefits of HIIT are well-documented, and translating this to an aquatic environment seems to amplify these benefits for certain populations,” Ashford said.

Ashford said adherence to exercise regimens is a critical factor in chronic disease management.

There are also limitations to water-based exercise.

“While effective for many, it might not suit all patients, especially those with certain types of chronic lung diseases, where the water pressure might pose breathing challenges,” Ashford said. “Also, accessibility to appropriate facilities can be a barrier for some patients.”

That said, Ashford said more research should be done to identify ways to make the water-based therapy more accessible to more people.

“AHIIT stands out as a potent, adaptable, and patient-friendly approach to managing various chronic conditions,” he said. “It combines the benefits of HIIT with the unique properties of water, offering a synergistic effect that can be particularly beneficial for patients struggling with land-based exercises.”