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Water properties and their use in therapy

Updated: Sep 30, 2023

It is well known that water has got many therapeutic properties that could be used to implement recovery and endurance.

Water properties include:

1. Buoyancy

2. Specific Gravity

3. Turbulence

4. Temperature

5. Resistance

6. Hydrostatic Pressure

7. Cohesion

8. Viscosity

Water temperature

Therapeutic effect on the patient can be achieved in temperature between 28°C and 32°C

When warm is applied to muscle tissue it causes: an increase in elasticity, increase in cell metabolism and blood flow and relaxation. This provides:

Pain relief

Increase in function or performance

Effective and comfortable exercise during the hydro session.

Specific Gravity (SG)/Density

SG is the density of a substance on the composition of the substances/object (the patient) and will depend on how well it will float on water.

The SG of water is 1,0, therefore if the SG of the object is >1,0 it will sink or if it is <1,0 it will tend to float.

· Water – 1,0

· Fat - 0,8

· Muscles =1

· Bone – 1,5-2


Buoyancy is based on Archimedes Principle:

“Upwards thrust of water acting on a body that creates an apparent reduction in body weight when immersed”

The deeper water = the greater buoyancy, however, deeper water increases the resistance to joint and limb movement

Cohesion/level of water

Exercising at the surface of the water is more difficult

If a patient is drawing their limbs close to the surface or lifting them out of the water – they will need to work harder.

The cohesive force is greater at the surface due to surface tension

The benefit of UWTM is that water can be adjusted according to a patient’s needs

Viscosity/thickness of the water

This is frictionless resistance due to the cohesive forces between molecules of a liquid. The viscosity of a liquid is significantly greater than air because the molecules in a liquid are more tightly packed together.

The viscosity of water increases drag forcing the patient to work harder when moving through the water

Viscosity may enable unstable animal to stand for longer periods, as falling over will take longer therefore they will have more time to rebalance themselves.


The disruption of the natural flow of water. Could cause detrimental effect – fatigue or/and lost of balance. On the other hand, it can improve balance, muscle strength and circulation!

As the patient moves through the water, they generate turbulence – this further increases the resistance to movement.


Resistance is surrounds us in the air and in the water. However, resistance is greater in water because molecules are more tightly packed together. Increased resistance to movement in the water can cause a patient to become more easily fatigued. The increased resistance during aquatic exercise can also be used in a beneficial way to promote muscle development and strength and improve cardio-vascular fitness.

Hydrostatic Pressure

Based on Pascal’s Law:

“Fluid will exert pressure on all objects that are submerged into it and this pressure is directly proportional to the depth and density of the water”

This is pressure felt when the body is fully or partially immersed in water


The pressure exerted can help to reduce oedema and localised swelling in the limbs and joints of the limbs. Which in turn promotes a healthier circulation and lymphatic flow which helps removal of toxins

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