Physiology and Immersion

This diagram shows what's happening in the body before a person enters the water, and what happens afterward. The changes are significant, especially those involving blood flow and the heart. The deeper a person is immersed, the more the health benefits increase. At neck level, even the brain is affected because more blood is forced upward from the lower extremities.

Click to see figure's text larger.

The heat and agitating water of a spa causes the heart to "stretch," imitating the effects of exercise. People in their 20s and 30s can experience as much as a 59 percent increase in increased blood flow, while soakers in their 40s and above see as much as a 22 percent increase. And the hotter the water, the greater the effect. (Of course, excessive high temperatures should be avoided.)

"The scientific community does much more research on pain than on pleasure," says Dr. Bruce Becker M.D., director of the National Aquatics and Sports Medicine Institute at Washington State University and a leader of several NSPF-funded studies. "My hope is that if we can do a good enough job in publishing this stuff, the heatlth-care industry will follow."*

 *Source: Pool and Spa News, November 14, 2008;100,102.