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Aquatic therapy

Principles of aquatic therapy

It is necessary to understand the basic principles and properties of water that include relative density, buoyancy, viscosity and resistance, and hydrostatic pressure to glimpse the benefits that aquatic therapy provides us.

Relative density

The relative density and specific gravity of an object determines how well that object will float. The specific gravity of water is 1; that of fat, lean muscle and bone are 0.8, 1 and 1.5 to 2 respectively. Therefore, if the specific gravity of an object is greater than 1, it will tend to sink, while if it is lower, it will float. That is why a thin animal, which is not moving, will have a tendency to sink faster than an obese one.


A body immersed in water is held in place by two forces, gravity and thrust. Thrust is the force that pushes the body upward, creating the false sensation of weight loss while the dog is submerged. The value of this force is the same as the weight of the animal. The thrust acts directly on the center of the thrust (which we can consider as the center of gravity of the submerged part), which does not have to coincide with the center of gravity. Our problem may be when the center of gravity and thrust are not in the same vertical, which can occur with inadequate placement of a float, causing the animal to tilt and be unable to maintain balance. The location of the thrust center depends on the percentage of body fat and the location of adipose tissue.

Pushing helps in the rehabilitation of weakened muscles and painful joints. It allows the patient to exercise in a vertical position and with reduced pain because they have to support less weight. This information is especially useful when dealing with animals with arthritis.

hydrostatic pressure

It is the pressure suffered by bodies submerged in a liquid or fluid simply by being immersed in it. Since hydrostatic pressure provides constant pressure on the body or leg immersed in water, it makes this an ideal environment to work with swollen joints or edematous tissues. Hydrostatic pressure opposes the tendency of blood and edema to pool in the lower areas of the body, therefore helping to reduce swelling.

Hydrostatic pressure also helps reduce pain during exercise. This is because it provides phasic stimuli (responses, reflexes or movements of rapid appearance and short duration) in the skin sensors that cause a decrease in the hypersensitivity of the nociceptors (neurons specialized in receiving pain) causing a decrease in sensation of pain, allowing the patient to execute different movements with less pain.

Viscosity and resistance

We could define viscosity as the resistance that a fluid opposes to movement within it. It is obvious that the viscosity of water is higher than that of air, making it more difficult to move through water than through air. This means that water provides us with the possibility of strengthening canine muscles and improving cardiovascular capacity. The resistance that water opposes is proportional to the speed of the movement that is carried out. It is also important in aquatic therapy for other aspects; It can increase awareness of movement which helps in stabilizing unstable joints. It also helps prevent falls, increasing the time the patient has to react, which in turn reduces the patient's anxiety. The combination of thrust and viscosity properties help keep the dog.

Piscina Hidroterapia

Benefits of aquatic therapy

Aquatic therapy has many benefits. Exercising in water is beneficial for developing strength, muscular endurance, cardiorespiratory endurance, range of motion, agility and mental well-being, all while minimizing pain. Gravity is the main resistance force when exercising on land, while viscosity, friction and turbulence are the main ones in water; These properties have a direct effect on heart rate and oxygen consumption.


Comparing subjects who exercise on land with those who exercise in water, the latter present a slightly higher heart rate and have a greater overall increase in heart rate due to the lower initial resting heart rate. Metabolic requirements are also greater in exercises performed in water. Patients can walk through the water at a slower speed and consume the same amount of energy. When we perform aerobic exercises in the rehabilitation process, they also contribute to cardiovascular well-being and weight loss. Exercises in water are also beneficial for muscle strengthening. Due to the push, walking on water can provide an excellent alternative to achieve and maintain muscle strength and range of motion in individuals with small joint problems such as osteoarthritis. Although exercises in water are not as effective in achieving maximum muscle development as if we did them on land, rehabilitation in water reduces joint effusion and leads to other improvements. Closed chain exercises, such as water walking, are more associated with everyday exercises than open chain exercises since they activate the muscles in a more functional way. Performing closed chain exercises in an environment where weight bearing has decreased can minimize or eliminate soft tissue damage or inflammation, while maximizing functional training. The aquatic environment can also help reduce knee pain and joint effusion, which facilitates the recovery of lower extremity function after anterior cruciate ligament surgery. The buoyancy of water also makes it easier to perform exercises while providing proprioceptive feedback that helps in the rehabilitation process. The effect of buoyancy (or thrust) allows gentle active exercises, reducing the load on damaged tissues. Aquatic exercises can be used as a transition to land exercises in post-surgical rehabilitation. These are normally less painful due to the support offered by buoyancy, which is why exercises in the water are less uncomfortable and provide a greater feeling of security when we begin active movements. This helps maintain range of motion and functional movement before they regain the strength needed to perform the same exercises out of the water.

There are also many physiological effects of exercising in heated water. Among them are increased circulation, increased joint flexibility and decreased joint pain. The decrease in pain and the daily improvement in the execution of activities has a significant impact on the general increase in the patient's functionality.

Water temperature also has a significant effect on the cardiovascular response to exercise. If the water temperature is low, peripheral vasoconstriction appears, blood moves towards the center, venous return improves and stroke volume increases. Therefore, to maintain the same cardiac performance, the heart rate decreases. Blood pressure is also altered by water temperature. On the other hand, exercising in water with a temperature higher than body temperature can increase cardiovascular demand.

The type of aquatic therapy used by therapists, veterinarians and owners will depend on the specific rehabilitation each individual needs. Knowing the benefits of aquatic therapy will help in prescribing specific protocols.

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