But for centuries, supporters of yoga, Zen Buddhism and other Eastern belief systems have maintained that body functions could be controlled through meditation and other thought processes. There are at least five different ways to measure body functions for biofeedback purposes. Most measurements are made through electrodes attached to various parts of the body. People can believe they are relaxed, while in reality their muscles may have remained tense without their awareness. It can help in healing muscle injuries, and in relieving chronic pain and incontinence.
Thermal biofeedback provides information about skin temperatures.
The temperature of skin is a good indicator of blood flow. EDA, or electrodermal activity, shows changes in perspiration rates. It is useful in the treatment of anxiety. Breathing is easy to monitor. In biofeedback, not only is the rate and rhythm of breathing measured, but the volume of air breathed in is measured as well.