Increasing interest in aquatic physical therapy can be attributed in part to its evolution from the limited confines of spas and “Hubbard tanks,” to the larger venues of swimming pools. These larger exercising areas accommodate a greater variety of exercises, including those that require sustained propulsive movements.
Using the water to regain lost mobility and strengthen weakened muscles has been described by a number of authors. The purpose of this article is to discuss the manner in which aquatic physical therapy is used for the treatment of common athletic injuries.
PHYSICAL PROPERTIES OF WATER AFFECTING AQUATIC PHYSICAL THERAPY
Two important physical properties of water, buoyancy and viscosity, are key elements in designing effective exercises for treating athletic injuries. The advantage of buoyancy is direct: When a person enters the water, there is an immediate reduction in the effects of gravity on the body. The advantage of viscosity of water is indirect: When the person moves through the water, resistance is felt. The degree of effort is determined by the size of the moving body, or limb, plus the speed or velocity of the movement.
Force of Buoyancy and Its Effect on Weightbearing During Immersion
The buoyant force of water decreases the effective weight of an individual in proportion to the degree of immersion. Axial loading on the spine and weight-bearing joints, particularly the hip, knee, and ankle, is reduced with increasing
depths of immersion.
When standing in chest-deep water, the weight-bearing load is approximately 40% of the total body weight, whereas stepping on a submerged step (waist-deep water) increases the weight-bearing value to approximately 60%.
The ability to control joint compression forces by varying degrees of immersion is of primary benefit in the design and prescription of therapeutic exercises. By monitoring the depths at which functional movements, such as walking and stepping, are performed, the effect of gravity can be reintroduced and, consequently, gradual strengthening is. When floating in prone, supine, or vertical positions, the effects of gravity are eliminated.
Muscle Strengthening Using the Viscosity of Water
Although traditional modes of strength training have been used successfully in clinical settings, there are three primary advantages for using water resistance to promote strengthening.
Water Acts as an Accommodating Resistance
The advantage of accommodating resistance is that it matches the patient’s applied force or effort. Because the resistance of the water equals the force exerted, the likelihood of exacerbation or reinjury is reduced dramatically.
Water Acts as a Variable Resistance
The term variable refers to being able to change the speed or velocity of the movement. Unlike isokinetic strength-training apparatus, which limit exercises to a preset velocity, it is possible to change limb speeds during each repetition in the water. Because most human motion is variable in nature, functional gains are more likely to be made.