Aquatic exercise is physical activity performed in water, and it is not the same thing as swimming lengths. Most of the research adults encounter under headings about swimming and health studied people walking, stepping and moving upright in chest-deep water, not people doing front crawl. That distinction runs through everything below.
Water changes four things about exercising: how much weight the joints carry, how much resistance each movement meets, how the body’s fluid sits, and how fast the body loses or gains heat. Those four properties are why aquatic exercise has been trialled in conditions where land-based exercise is painful or difficult, including osteoarthritis of the knee and hip, fibromyalgia and chronic low back pain, and why it has also been examined against blood pressure and blood glucose.
This guide explains what aquatic exercise is, what water changes about exercising, and what the research on swimming and water exercise for health conditions does and does not show. It is not medical advice, and it deliberately leaves out the outcome figures those studies report, for reasons explained below.
What Is Aquatic Exercise?
Aquatic exercise is physical activity performed in water, usually at a depth between the waist and the shoulders, in which the water supports part of the body’s weight and resists every movement. It covers four common forms:
- Water walking: walking forwards, backwards and sideways in chest-deep water
- Structured aquatic exercise classes: group sessions of upright movement, often called aquafit or water aerobics
- Aquatic physiotherapy: individual sessions led by a physiotherapist, sometimes in a heated pool
- Swimming lengths: horizontal, continuous, using recognized strokes
The first three are what most published research examines. Swimming lengths is the form most people picture and the least studied of the four in this context. A reader who assumes the research is about front crawl will draw conclusions the research does not support.
Aquatic exercise also has no ability requirement at the shallow end. Water walking, shallow-water classes and most aquatic physiotherapy are all available to an adult who cannot swim at all. Only swimming lengths requires a stroke. The wider case for swimming as exercise, separate from any condition, is set out on the benefits of swimming page.
Aquatic exercise is defined by where it happens. What that changes is physics.
What Does Water Change About Exercising?
Water changes four things about exercising: how much of a person’s weight their joints carry, how much resistance every movement meets, how the body’s fluid is distributed, and how quickly the body loses or gains heat. Every difference between exercising in a pool and exercising on land traces back to one of those four.
The first is buoyancy.
Buoyancy and Joint Load
Buoyancy is the upward force water exerts on a submerged body, and it offsets a large part of that body’s weight. The deeper a person stands, the more of their weight the water carries, so a movement performed in chest-deep water loads the knees, hips and spine far less than the same movement performed on a floor.
Arthritis Society Canada describes the effect directly: “the buoyancy of the water also takes the weight off painful joints”, and “walking, jogging or running in water offers the same benefits of those activities on land, just without the impact on joints”.
What buoyancy does is reduce load. That is a mechanical statement about force, and it is the whole of what can be said with confidence. Reduced load is the reason aquatic exercise is studied in joint conditions. It is not, by itself, a result for any individual person.
Buoyancy removes load. Pressure and drag add something instead.
Hydrostatic Pressure and Drag
Hydrostatic pressure is the inward force water exerts on a submerged body, and it increases with depth. Drag is the resistance a body meets when it moves through water. It comes mainly from water’s density (roughly 800 times that of air), with a smaller contribution from its viscosity.
Drag is why every movement in a pool meets resistance in every direction. On land, a leg lift is resisted on the way up and assisted by gravity on the way down. In water, both directions meet resistance, and buoyancy, not gravity, decides which one is easier. That resistance also rises with speed, which means a movement in water is self-limiting: moving faster is harder, and slowing down immediately reduces the effort, without any equipment to adjust.
Hydrostatic pressure acts continuously on the chest, abdomen and limbs while a person is immersed. It is the reason breathing feels different in the water and the reason immersion is a genuine physiological state rather than a figure of speech.
Pressure and drag are the same in any pool. The temperature is not.
Water Temperature
Water temperature varies more between pools than any other property, and it is the one most worth checking. A Toronto aquatic physiotherapist quoted by Arthritis Society Canada says that “generally, 90 to 92°F (32 to 34°C) is a neutral comfortable temperature” for water therapy.
A standard lap pool is usually cooler than that, commonly in the range of 26 to 28°C (79 to 82°F), because swimmers doing continuous lengths generate heat and a warm pool becomes uncomfortable quickly. A therapy pool and a lane pool are therefore different environments for the same activity.
Neither temperature is correct in general. Warmer water suits slow upright movement. Cooler water suits continuous swimming. An adult choosing between two facilities is often really choosing between two temperatures, without knowing that is the choice being made.
Those properties are why aquatic exercise has been trialled in conditions where land exercise is difficult.
Which Conditions Has Aquatic Exercise Been Studied In?
Aquatic exercise has been trialled most often in three conditions where land-based exercise is painful or difficult: osteoarthritis of the knee and hip, fibromyalgia, and chronic low back pain.
Studied in is not the same as proven for. None of the reviews below concludes that aquatic exercise treats a condition. Each reports what happened to groups of trial participants following a supervised protocol, and each names limits in its own evidence. Those limits are reported here alongside the findings, because a summary that carries the finding without the limit is not a summary of that research.
The summaries below are deliberately short. Each review is linked in full in the Sources section at the end.
Osteoarthritis of the Knee and Hip
A Cochrane review led by Bartels and colleagues, published in 2016, pooled 13 trials covering 1,190 participants with knee or hip osteoarthritis. The review found “moderate quality evidence that aquatic exercise may have small, short-term, and clinically relevant effects on patient-reported pain, disability, and QoL”. Three words in that conclusion carry weight and are usually dropped when it is quoted: small, short-term, and patient-reported.
Fibromyalgia
A Cochrane review led by Bidonde and colleagues, published in 2014, examined 16 studies covering 881 people with fibromyalgia, of whom 866 were women and 15 were men. The review reported that “low to moderate quality evidence relative to control suggests that aquatic training is beneficial for improving wellness, symptoms, and fitness in adults with fibromyalgia”, and that “no serious adverse effects were reported”, while also noting that adverse effects were poorly reported. The sample is almost entirely female, which the review states plainly.
Chronic Low Back Pain
A systematic review and meta-analysis by Ma and colleagues, published in BMC Musculoskeletal Disorders in 2022, covered 13 articles and 597 patients with chronic low back pain. The authors concluded that aquatic physical therapy “could benefit patients with chronic low back pain”, and immediately added that “because the articles included in this systematic review have high bias risk or are unclear, more high-quality randomized controlled trials are needed to verify”. The authors also rated the certainty of the evidence as low or very low. Both caveats came from the authors, not from this page.
Those three are musculoskeletal. A second body of research looks at measures taken in a clinic.
What Research Says About Blood Pressure and Blood Glucose
Aquatic exercise has been examined against two measures taken in a clinic rather than reported by a patient: blood pressure and HbA1c. Both are measured rather than self-reported, which makes this research harder to dismiss and easier to misuse.
Igarashi and Nogami published a meta-analysis of regular aquatic exercise and blood pressure in the European Journal of Preventive Cardiology in 2018, pooling 14 randomized controlled trials covering 452 participants. Rees, Johnson and Boulé published a meta-analysis of aquatic exercise in adults with type 2 diabetes in Acta Diabetologica in 2017, pooling 9 trials covering 222 participants and examining HbA1c, the blood test that reflects average blood glucose over roughly three months. Four of those nine trials had no comparison group at all.
Both reviews report numeric changes. This page does not reproduce them, and the reason is worth stating rather than hiding.
A figure from a meta-analysis is an average across a trial population, produced under a supervised protocol, over a set number of weeks, in people who met specific inclusion criteria. Printed on a page like this one, that same figure reads as a prediction of what will happen to the reader. It is not one, and no honest framing of it makes it one. The numbers belong in the papers, where the methods sit next to them.
The other thing worth saying is that 452 and 222 are small numbers for cardiometabolic research. Both reviews are real, both are peer-reviewed, and both are smaller than the confidence with which they are usually cited.
What can be said without any of this difficulty: aquatic exercise is exercise, it can be sustained at a moderate intensity for a long time, and it is available to adults for whom land-based exercise is not. Blood pressure and blood glucose are topics on which that research exists. They are not outcomes this page offers.
Research describes populations. A pool is a specific building.
What to Check About a Pool Before You Start
Six facts about a pool decide whether it suits an adult with a long-term condition, and none of them appears in a program description. Each is a question worth asking the facility directly:
- What temperature is the water kept at? The difference between a therapy pool and a lane pool is several degrees, and it changes which activity is comfortable.
- How deep is the shallow end? Chest depth for one adult is shoulder depth for another, and the depth decides how much weight the joints carry.
- How do people get in and out? Steps with a handrail, a ladder, a graded ramp and a hoist are four different answers, and only one of them suits some adults.
- Are the change room and pool deck accessible? Distance from the change room to the water, bench seating, and non-slip surfaces matter more than the pool itself for some people.
- Is a staff member on the deck during the session? Supervision is not the same as a lifeguard being somewhere in the building.
- How busy is the pool at that time? An adult moving slowly in a lane shared with four continuous swimmers has a different session from the same adult in an off-peak hour.
Rocket Swim Club can answer all six for any of its Toronto pools before a first session. Ask when you get in touch.
An adult who cannot yet swim comfortably is better served by instruction than by an open lane, and Rocket Swim Club’s adult swimming lessons, run at pools across Toronto’s west end, are available one to one as well as in a group.
Those questions are answerable by the facility. One is not.
Why to Speak to a Doctor First
A doctor is the only person who knows both the condition and the person. This page knows neither, and no page can.
There is a specific physiological reason rather than a general caution. Arthritis Society Canada notes that “exercise in water can lower blood pressure and heart rate, so consult with your health care provider first”. Immersion is not a neutral environment. It shifts fluid toward the chest, changes the work the heart is doing, and can add to the effect of medications that already lower blood pressure or heart rate. An adult taking medication that affects blood pressure or heart rate has a genuine question to ask, and it has an answer that depends on the medication.
Three things are worth asking before a first session: whether immersion interacts with any current medication, whether there is a depth or a water temperature to avoid, and whether any particular movement or stroke should not be attempted. All three have short answers, and all three are specific to one person.
An adult who has been told to exercise and has found land exercise painful is exactly the reader this page is written for. The next step for that reader is a conversation with their own clinician, not a decision made from a web page.
Questions Adults Ask Before a First Session
Is swimming good for arthritis?
Water exercise is widely recommended by arthritis organizations, but most of the evidence is for upright aquatic exercise rather than swimming lengths. The Cochrane review on knee and hip osteoarthritis described above found small, short-term benefits for pain and function, and Arthritis Society Canada points to buoyancy taking weight off painful joints. Whether swimming lengths suits a particular joint, and which strokes to avoid, is a question for a doctor or physiotherapist.
Is water walking as useful as swimming lengths?
They are different activities studied for different reasons. Water walking is upright, slower, easier to control and easier to stop, and it is what most of the research described above actually examined. Swimming lengths is continuous, horizontal, harder to pace, and requires a stroke. For an adult starting from nothing, water walking is the form that needs no ability, no equipment and no instruction, which is why it is usually where people begin.
What if you cannot swim?
Nothing in the shallow end requires swimming ability. Water walking, standing movements and supported exercise all take place where a person can stand, and an adult who cannot swim at all can do every one of them. Swimming lengths is a separate skill, and it is a learnable one at any age. Rocket Swim Club’s swimming lessons start from no ability, and one-to-one sessions are available for adults who would rather not learn in a group.
Is a warm pool always better?
No. Warmer water suits slow, upright movement and is what therapy pools are heated for. It becomes uncomfortable during continuous swimming, because a swimmer generates heat and has nowhere to lose it. The right temperature depends on the activity, not on the person’s condition alone.
Can you do aquatic exercise on a bad day?
That is a question for a clinician, not for a swimming club. What is worth saying is that a bad day is not a failure of the plan, and that the six pool questions above matter most on exactly those days: how far the change room is, whether there is a handrail, and how busy the water is. An adult who has thought about those in advance has more options on a bad day than one who has not.