Hydrostatic pressure from immersion in water forces more blood to the central organs, increasing cardiac stroke volume and cardiac output, which is a similar effect caused by exercise. In addition, immersion also impacts liver and hormone production (endocrine system) and respirator exercise to breathe against the pressure imparted by the water. As with any exercise, increasing activity provides additional benefits. Yet with aging and growing sedentary populations who are less prone to exercise, immersion or light activity in the water are ideal to gain heart, respiratory, and relaxation benefits with minimal risk of injury. (Comprehensive Aquatic Therapy, Ch. 2. Biophysiological Aspects of Hydrotherapy, WSU Publishing, 2011).
The above data was shared at the Learn-To-Swim Innovator Meeting in Colorado Springs Colorado on April 25, 2012. This meeting was sponsored by the National Swimming Pool Foundation.