top of page

Aquatic Exercise: Dangerous waters for the cardiopulmonary patient?

Byline: Andrea Salzman, MS, PT

It strikes terror into the most phlegmatic of pool managers: The sight of a motionless body hovering beneath the water’s surface.

But the truth is worse than imagined. Patients who suffer heart attacks or brain infarctions or other significant cardiorespiratory events do not flounder about the surface of the pool. They do not yelp out plaintively. They do not splash copious amounts of water. They slip, often unnoticed, silently into the depths.

And this (literally) heart-stopping possibility has kept doctors from sending cardiac – and even respiratory – patients to aquatic therapy for a generation.

Well, it may be time to rethink that policy.

Over the last ten years, researchers have delved into the reality of what can make a swimming pool a dangerous place for cardiopulmonary patients. Armed with this knowledge, the well-informed Y or JCC facility operator can correct many of the most egregious misperceptions, including the following.

1. Swimming and aquatic vertical exercise should be lumped into the same risk category. 

Swimming – especially for the novice or marginal swimmer – does require extremely high oxygen demands and can easily bump a compromised patient into near maximum VO2 levels. It can be a risky aerobic exercise for the unskilled or marginal swimmer.

Vertical aquatic exercise, on the other hand, has a shallower learning curve. It requires less skill, less energy expenditure and less coordination to execute. More importantly, the effects of hydrostatic pressure on the immersed legs create a pressure gradient which propels blood up to the chest. This results in greater myocardial perfusion and makes for a more efficient cardiac output.

2. Individuals exercising in water should use land-based models for calculating training heart rates. 

The traditional Karvonen method for determining exercise intensity (220 - your age x 60%-80%) is grossly inadequate for use in the pool, especially for the cardiopulmonary compromised patient. The hydrostatic pressure gradient present during vertical exercise allows the heart to expel a larger quantity of blood with each compression. This improved stroke volume permits the heart to beat less frequently for a given cardiac output. Thus, aquatic target heart rate zones should almost never mimic their land-based counterpoints; instead they should be established at a slower rate, perhaps as slow as 12-17 beats per minute fewer.

3. Individuals with low vital capacities will become dangerously short of breath during vertical immersion in water. 

The same hydrostatic pressure of the water which promotes improved cardiac return may prevent adequate chest expansion in a respiratory –compromised patient. This may make breathing difficult. However, there are three simple options to remedy this situation. Exercise in shallower water. Exercise in a supine position (usually supported with floats). Or intermittently use this increased resistance as a progressive resistive exercise program for the diaphragm and intercostal muscles.

4. Individuals with poor thermoregulation capacity will gain heat rapidly during immersion in “hot” therapy pool temperatures.

In truth, most therapy pools (and all traditional swimming pools) use water which chills the body during quiet immersion. A pool must be heated to 93-95° Fahrenheit in order for an individual at rest to gain heat during immersion. However, if a patient begins to exercise vigorously in relatively warm water (warmer than 89-90°) care should be taken to allow radiation and evaporation to occur. This can be accomplished by keeping the head uncovered, keeping humidity near or below 50%, and allowing rest breaks.

Creating a safe aquatic environment

Therapists who choose to use the relatively cooler waters available at the local Y or JCC pool will be able to create more vigorous aerobic challenges for their cardiopulmonary patients. That said, there are still many potential roadblocks to servicing this population’s needs in the pool. Here are some quick rules-of-thumb for the therapist contemplating taking the plunge.

Bring all emergency meds poolside. 

Imagine a scenario where a patient with COPD has an asthma attack while exercising in the pool. This is not the time to extract the patient’s locker combination (between wheezes) in order to obtain his inhaler. Rescue inhalers, nitroglycerin tablets, and glucose supplements should always be brought pool-side.

Restrict horizontal exercise.

Horizontal movement in water (swimming) is a skilled activity and can be aerobically demanding. The poorly efficient swimmer may reach VO2s of over 90% max. Swimming should not be attempted unless the patient already has strong swimming skills and is cleared for swimming by his doctor.

Use rating of perceived exertion or the “talk test”.

If the patient takes medications which artificially elevate or decrease the heart rate, or he has been fitted with a pacemaker, neither the Karvonen formula nor any of the “modified” formulas are appropriate to establish heart rate parameters for exercise. Instead, the patient should be taught to use a rating of perceived exertion (RPE) such as that described by Borg. Alternatively, patients can use the talk test to determine if they are overly taxed. Individuals unable to easily speak in sentences may be exercising beyond their target zone.

Encourage breaks.

Encourage breaks — even breaks out of water — if the water is near thermoneutral (93-95°) and the exercise is vigorous. Initially, exercise should be of low intensity and short duration. Angina response should be respected and any progression of exercise intensity and duration should be conservative (Note: initial angina may be from anxiety, not immersion or exercise). Water for drinking should be kept pool-side and patients should be encouraged to drink at least 8-12 ounces of water before leaving the pool.

Prepare for the unexpected.

All aquatic participants should have a medical release regardless of the remoteness of cardiac or respiratory difficulties. Have CPR and emergency plans posted for staff and patients. Never leave patients unattended even if states codes do not require a lifeguard to be present on deck. In fact, whenever possible, have at least two staff members present in the pool area at all times to allow one staffer to address emergencies while the other seeks help and manages other patients in the pool.

 Aquatic therapy has much to offer. Be safe, be wise, but most of all, be aware that the benefits often outweigh any risks for this population. Do so and you may just make your facility the “go to pool” for the cardiac and respiratory patient.


Therapists interested in the latest research on the benefits (and risks) of vertical aquatic exercise for this population will be interested in several articles currently available,


1. Cider, A.; Svealv, B.G.; Tang, M.S.; Schaufelberger, M.; Andersson, B. Immersion in warm water induces improvement in cardiac function in patients with chronic heart failure. Eur J Heart Fail. 2006: 8(3): 308-313.

2. Cider, A.; Sunnerhagen, K.S.; Schaufelberger, M.; Andersson, B.  Cardiorespiratory effects of warm water immersion in elderly patients with chronic heart failure. Clin Physiol Funct Imaging. 2005; 25(6): 313-317.

3. Schoenhofer, B.; Koehler, D.; Polkey, M.I. Influence of immersion in water on muscle function and breathing pattern in patients with severe diaphragm weakness. Chest. 2004; 125(6): 2069-2074.

4. Wadell, K.; Sundelin, G.; Henriksson-Larsen, K.; Lundgren, R. High intensity physical group training in water--an effective training modality for patients with COPD. Respir Med. 2004; 98(5): 428-438.

5. Cider, A.; Schaufelberger, M.; Sunnerhagen, K.S.; Andersson, B. Hydrotherapy - a new approach to improve function in the older patient with chronic heart failure. Eur J Heart Fail. 2003; 5(4): 527-535.

 6. Pechter, U.; Maaroos, J.; Mesikepp, S.; Veraksits, A.; Ots, M. Regular low-intensity aquatic exercise improves cardio-respiratory functional capacity and reduces proteinuria in chronic renal failure patients. Nephrol Dial Transplant. 2003; 18(3): 624-625.

20 views1 comment

1 Comment

Interested in similar aquatic therapy research? Read up on the effect of aquatic exercise on mental health, functional autonomy, and oxidative dysfunction in hypertensive adults here: Da Silva, L. A., Menguer, L., Motta, J., Dieke, B., Mariano, S., Tasca, G., … Aurino, P. R. (2017). Effect of aquatic exercise on mental health, functional autonomy, and oxidative dysfunction in hypertensive adults. Clinical and Experimental Hypertension, 1–7.

bottom of page