Improving a Patient's Strength and Range of Motion with Aquatic Therapy


Published: 25 October 2017

Pick up a recent journal which deals with rehabilitation and odds are there will be an article on aquatic therapy.

Look closely. Kick back in your most delightful chair (move the cat) and read that baby from start to finish. Done?

Now tell me why the aquatic intervention worked. Can’t find that piece of information?

I’m not surprised. In many articles, they just don’t tell you. It’s as if the pool is this great big black box and all things which occur inside it are unknowable. In fact, often the article doesn’t even describe what kind of interventions were done in the pool. It is all lumped into the phrase ‘pool therapy’ or ‘aquatic rehab’. It is as if all things done in water become equal.

Think about the words themselves. Aquatic therapy. It’s such an ambiguous term. What does that phrase tell us, really? It tells us that the goal was rehabilitation and that the patient got wet. It tells us as much as if I documented a physiotherapy visit by describing the session as “dry land intervention” or “Terra Firma Physio”.

Clearly, if we are to determine if aquatic therapy is effective, we must first be square on what we mean by aquatic therapy and why we think the formula: immersion plus effort is a winning proposition.

In Part 1 of this series, we discussed the fact that aquatic therapy offered clinicians the opportunity to reduce weight bearing and joint compression for their clients. In this article, we will be asking why it is often better to do strength training and ROM treatments in water.

Improving a Patient's Strength and Range of Motion with Aquatic Therapy

So what is our working hypothesis for why water works?

It is our contention that immersed bodies are affected by the buoyancy and viscosity of the water in which they are immersed. These properties combine to create a therapeutic environment in which the patient’s weakness and loss of range of motion can be effectively treated.

Let’s try and make a case for immersion

Why is the pool considered such a wonderful place for addressing weakness and range of motion (ROM) restrictions? Two reasons: buoyancy and viscosity.


First, let’s consider buoyancy. As already described in Part 1, the therapeutic pool offers a buoyant environment, permitting greater movement freedom for those who do not have the strength to operate under gravity’s full effect. If the patient is in a cycle of immobility spiralling towards a greater loss in ROM and strength, exercise in water will help interrupt this cycle.

Buoyancy can also promote ease of handling of the patient, allowing access to body parts which would be inaccessible if the patient was positioned on a plinth or chair.

The therapist can use buoyancy to create a low-friction environment for exercise training and to float patients in a supine position. These positions make it possible to manipulate joint and soft tissue stretches and to craft innovative strength challenges, by allowing the progression of resistance in a logical, graded fashion.

Finally, buoyancy makes it possible for patients with impaired motor function (for instance, the inability to have normal scapulohumeral rhythm when raising the arm) to challenge both quantity and quality of movement between and across body segments. Because the arm weighs so much less, it may be possible for the patient to execute near normal kinematics of the shoulder joint while immersed.


Next, let’s consider viscosity. When people think about working in water, they typically think about the ease that comes with buoyancy. What they fail to take into account is that water’s viscosity can create a massive amount of resistance. Viscosity is nothing more than the inherent friction that exists between molecules of a liquid which cause a resistance to flow. Molecules of a liquid adhere to the surface of any body moving through that liquid, resulting in resistance.

It is possible to use this viscosity therapeutically. Slow-velocity movements (<45°/second) performed in an aquatic environment create less resistance than when performed on land. The skilled therapist can instruct the patient in a series of rhythmic motions which increase joint nutrition and bathe the joint in synovial fluid. This can assist in decreasing joint and soft tissue swelling, inflammation and/or restriction and increasing joint mobility.

If instead, the patient is instructed to move rapidly (>60°/second), the inherent molecular friction between the water molecules will increase the resistance of movement. In that way, rapid-velocity activity and exercise in an aquatic medium can be used for strength training.

Plyometric studies have demonstrated that it is possible to create the same dynamic forces in water as on land — without the weight bearing complications. And — although the water provides a reduced weight-bearing environment — this does not mean that water-based exercise will result in less bone stimulation than land-based exercise.

Bone growth and retention is stimulated by two factors—impact and muscular pull on the bone. Exercise in water — especially fast moving exercise using resistive devices such as a bell or paddle — will create considerable muscle pull on the bone, stimulating bone.

Finally, the water allows rapid changes in velocity, direction, and resistance. Strength training in the pool is predominantly concentric in nature (unless buoyant devices are employed) which means there will be less delayed onset muscle soreness. Mixed-velocity activity and exercise in an aquatic environment can challenge motor control and motor learning. Water-based resistance is hard to predict and thus provides a training opportunity for the skilled clinician.

It is also possible to use the concepts of flow to decrease resistance by taking advantage of the “pull” of wake or by performing movements in a more streamlined position. All of these properties can be harnessed therapeutically, making the pool the ideal location for addressing weakness and loss of ROM in orthopaedic and neurological populations.

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