Biofeedback training is a method of learning how to consciously regulate normally unconscious bodily functions (such as breathing, heart rate, and blood pressure) in order to improve overall health. It refers to any process that measures and reports back immediate information about the biological system of the person being monitored so he  can learn to consciously influence that system. 

  Biofeedback is useful for reducing stress, eliminating headaches, controlling asthmatic attacks, reconditioning injured muscles, and relieving pain. Biofeedback training teaches a person how to change and control his body's vital functions through the use of simple electronic devices. 

  The idea that a person can learn to modify his own vital functions is relatively new. Before the 1960s, most scientists believed that autonomic functions, such as heart rate and pulse, digestion, blood pressure, brain waves, and muscle behavior, could not be voluntarily controlled. Recently, biofeedback, along with other methods of self-regulation, such as guided imagery, progressive relaxation, and meditation, has found widespread acceptance among physiologists and psychologists alike.