There are three important components of using water as a therapy to decrease pain and re-habilitate, they are buoyancy, resistance, and drag and turbulence. Buoyancy is defined as the upward thrust your body receives in the water which is the opposite of the downward thrust the body experiences on land due to gravity. With this buoyancy the force of compression on the joints is decreased dramatically, making it possible to reach full range of motion. The water acts like a natural support for all the limbs easing the pressure on joints even further. All of this means that it is possible to move and exercise in water with little risk of injury.
Resistance is defined as a force that works against the muscle making it work harder.
Water is denser than air and increases the resistance on the muscles by 12. It is possible to build greater strength in the water than on land due to the resistance factor and the lack of land gravity. Drag creates opposition to the movements of the limbs in the water. Turbulence is the agitation of the surrounding water that can be created in the water that can be used as a hydromassage effect. Water therapy uses the elements of stretching, exercise and massage to reach its goals.