Physiological Effects of Exercise in the Water

Aquatic training provides an exercise modality for fitness and rehabilitation. The properties of water provide support, resistance and assistance in a training program. An aquatic training program can decrease compression, vibration and torsional forces that occur when training on land. The properties of water influence the body during exercise and at rest. Here are just a few examples.

Buoyancy

Buoyancy lets participants experience a partial-floating feeling when entering the pool. The water creates pressure and pushes a person up, which is valuable for a person who does not want to place his whole body weight on a specific body part. The deeper the water, the less weight one has to support with his own body. The buoyancy of water reduces the "weight" of a person by up to 90 percent depending on body composition, muscular structure and depth of water, which reduces stress on joints and connective tissue. Buoyancy can be used to aid or resist exercises depending on the desired effect. Buoyancy assists individuals with lower-body or spinal injuries, pregnant individuals and those with physical limitations.

Hydrostatic pressure

Hydrostatic pressure is the pressure exerted by the water on an object immersed in the water. The deeper an object is submerged, the more pressure there is on that object. Using hydrostatic pressure is used do decrease excessive edema or swelling and is also beneficial for breathing. The hydrostatic pressure on the chest wall resists muscles that expand the chest for breathing, increasing the capacity to inhale oxygen out of the water.

Viscosity

Viscosity is resistance between the water molecules, effecting how it flows. Water is 790 times more viscous and provides 12 times the resistance than the air normal exercise is performed in. This provides ways to create resistance without overloading muscles or joints. Moving through the water, a body creates drag as water molecules attempt to "stick" to the body, while also trying to stick to other water molecules. Because of the water's viscosity, equipment used will increase the resistance increasingly with size. Increasing the speed of an exercises will also increase the resistance of the exercise.

Thermal regulation through convection

One factor associated with exercising in water is the ability to regulate body temperature. Optimal water temperature for aquatic exercise is between 80 and 86 degrees Fahrenheit. Water below 78 degrees may not be appropriate for exercise as it may impede the ability to maintain optimal body temperature. Water temperatures above 88 degrees may be too warm and speed up fatigue. When the body is submerged in water, heat loss via conduction is 26 times greater compared to a similar air temperature.