The Importance of Water Therapy in a Physical Rehabilitation Program

Stephanie Thomovsky, DVM, MS, DACVIM (Neurology), CCRP
Clinical Assistant Professor of Neurology and Neurosurgery at Purdue
Director of Physical Rehabilitation Purdue

Physical rehabilitation (PR) is an up and coming aspect of veterinary medicine and veterinary care.  Though its use is widespread, its validity has been studied only in a few veterinary reports to date.  PR techniques are utilized in orthopedic patients, neurologic patients, arthritic patients and obese dogs.  An important aspect of physical rehabilitation is water therapy.  Water therapy is regularly utilized in human rehabilitation as a mainstay of care.  In veterinary medicine water therapy mainly comes in the forms of swimming and underwater treadmill walking or running.

There are many benefits of water therapy.  These include:  the warming effect of water, pain reduction, heat dissipation, improved circulation, increased metabolism, complete use of all body muscles, and improved joint range of motion.  Water therapy also helps with muscular balance all while providing a low impact environment for joints and muscles.  Perhaps most importantly, however, water is a fun environment in which to work and play.

In human medicine there are 10 accepted proven benefits of swimming and exercises that involve water.  One of the main benefits is an improved life expectancy; those who swim have a 50% lower death rate than those individuals who run or walk for exercise or those who do not exercise.  Water therapy has been proven to reduce stress; swimming is associated with endorphin release and the replacement of new neuronal cell bodies in the brain destroyed secondary to stress.  Those individuals who swim are at a lower risk of diabetes, high cholesterol and heart disease.  The warm, moist environment of swimming pools is helpful to those with a variety of respiratory system abnormalities such as asthma.  Swimming also is proven to increase flexibility, allowing joints, muscles and ligaments to remain elongated and loose.  Strength of muscles and bones is improved in water in less time as water is twelve times denser than air.  This density helps to build muscle and strength in a reduced time.  Swimming is also beneficial to weight control and weight loss as it effectively increases metabolism.

There are many properties of water that make it an ideal medium in which to exercise.  Those properties include:  viscosity, resistance, hydrostatic pressure, fluid dynamics, buoyancy and the temperature of the water.  As state previously water is denser than air.  It is also 15 times more viscous than air.  This increased viscosity allows animals that are weak to stand and walk with less assistance, helping to build confidence.  This confidence is especially important in post-operative recovery.  The viscous nature of the water also helps support the patient and allows them to improve strength, tone and fitness while walking less.  This viscosity adds to the resistance that one feels when moving in water as compared to air. 

Resistance is both dependent on surface area and also the speed of water flow.  The surface area is dependent on water depth; the addition of equipment can also increase the surface area of the patient.  When more surface is in contact with the water, there is added resistance to movement.  Equipment such as weights or parachutes add drag and increase resistance when moving through the water.  The speed the patient is moving through the water also affects resistance.  The patient’s speed is dependent on their own volitional movement, while water speed is controlled with jets and, in a treadmill setting, the speed of the belt.  Though resistance makes movement for the patient more difficult, it also means that the patient can, with less activity and less time more efficiently improve strength, tone and fitness. 

Hydrostatic pressure is affected by the density of the water and also the depth of submersion.  Pascal’s law states that the fluid pressure exerted on all immersed body surfaces is equal at any given depth.  The pressure exerted by water on the patient can be utilized to reduce limb edema, allow for improved blood flow from the periphery and helps reduce nociceptor sensitivity.  Other key principles of water that influence its use as a tool for effective rehabilitation include basic fluid dynamic principles.  Movement through water is affected by laminar flow, Current and the turbulence affect ease of movement through water and resistance.  Increased resistance is created secondary to increased friction, water eddy formation and drag.  The amount of drag experience by a patient is dependent on body size and hair length.  Imagine a Puli walking on an underwater treadmill versus a Chihuahua.  It would be much more challenging for the former as compared to the later as he will have more resistance to movement because of both body size and hair length.  The hydrodynamic forces of water create a differential in pressure between the thoracic limbs which are under higher pressures versus the pelvic limbs, under lower pressures.  This pressure difference and water friction help to test balance and also strengthen postural muscles.

Buoyancy is another important property of water.  Archimedes stated that a submerged body in water experiences an upward thrust that is equal to the weights water displaced.  The degree of buoyancy is dependent on water depth and an animal’s buoyancy affects weight bearing and compressive forces on his joints.  Buoyancy challenges balance and proprioception but also helps lighten an animal so that movement is easier.  In patients in which paresis is a component of their disease, buoyancy can really make movement easier. 

The ability to control water temperature is also an asset when it comes to devising a physical rehabilitation plan.  Warm water can improve circulation, increase calorie expenditure, improve the elasticity of soft tissue, as well as improve coordination, proprioception and nerve conduction velocity.  There is also evidence that submersion in warm water improves mood and relieves pain. 

To date there are only few peer reviewed research reports in veterinary medicine regarding the use of water therapy in physical rehabilitation.  That being said Levine D et al, (2010) published a novel report that sought to look at PR using an underwater treadmill.  He showed that when a dog is immersed at the level of the greater trochanter he carries 38% of his own weight, at the level of the femoral condyles he carries 85% of his weight and at the level of lateral malleolus, he carries 91% of his own weight.  This information is extremely helpful as the underwater treadmill, in a commonly used tool in veterinary PR.

Water therapy is often recommended as an adjunct to neurosurgery and conservative management of a variety of neurologic conditions in dogs.  Water therapy has also been studied in a few publications dogs recovering from orthopedic surgery or those dogs being medically managed with orthopedic disease such as osteoarthritis.

As previously stated, there are two main ways that water therapy is implemented in canine rehabilitation.  One is via use of an underwater treadmill and the other swimming in a pool.  Both types of water exposure have different benefits.  Underwater treadmill allows for active range of motion that mimics motion on land, however joint flexion is mildly improved in water as compared to land.  Water provides the added benefit of warmth, buoyancy decreased joint compression and resistance as compared to land walking.  There is also something to be said for building confidence in water, especially in patients with varying degrees of paresis.  Often tetraparetic animals, for example are nervous to attempt to walk on land for fear of falling.  The friction and buoyancy of water allow for movement with less risk of falling and injury.  Swimming shares similar benefits of underwater treadmill walking but with complete lack of weight bearing and concussive forces.  Flexion is greatly improved when dogs swim as compared to walking in any medium.  This is important for patients recovering from muscle contracture or orthopedic conditions resulting in reduced joint flexion.  Swimming these patients allows for active range of motion and improved flexion and can speed recovery.

In summary, water therapy is a beneficial tool for veterinary rehabilitation.  When properly performed it carries little risk to the patient but is of great benefit.  As time goes on and the use of water therapy becomes more and more common, hopefully, more veterinary studies will be performed assessing its benefit. 


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