Good overview of biofeedback therapy:

When you raise your hand to wave hello to a friend, or lift your knee to take another step on the Stairmaster, you control these actions. Other body functions -- like heart rate, skin temperature, and blood pressure -- are controlled involuntarily by your nervous system. You don't think about making your heart beat faster. It just happens in response to your environment, like when you're nervous, excited, or exercising.

One technique can help you gain more control over these normally involuntary functions. It's called biofeedback, and the therapy is used to help prevent or treat conditions including migraine headaches, chronic pain, incontinence, and high blood pressure.

How Does Biofeedback Therapy Work?

Researchers aren't exactly sure how or why biofeedback works. They do know that biofeedback promotes relaxation, which can help relieve a number of conditions that are related to stress.

During a biofeedback session, electrodes are attached to your skin. These electrodes send signals to a monitor, which displays a sound, flash of light, or image that represents your heart and breathing rate, blood pressure, skin temperature, sweating, or muscle activity.

When you're under stress, these functions change. Your heart rate speeds up, your muscles tighten, your blood pressure rises, you start to sweat, and your breathing quickens. You can see these stress responses as they happen on the monitor, and then get immediate feedback as you try to stop them.

A biofeedback therapist helps you practice relaxation exercises, which you fine-tune to control different body functions. For example, you might use a relaxation technique to turn down the brainwaves that activate when you have a headache.

Several different relaxation exercises are used in biofeedback therapy, including:

Deep breathing

Progressive muscle relaxation -- alternately tightening and then relaxing different muscle groups

Guided imagery -- concentrating on a specific image (such as the color and texture of an orange) to focus your mind and make you feel more relaxed

Mindfulness meditation -- focusing your thoughts and letting go of negative emotions

As you slow your heart rate, lower your blood pressure, and ease muscle tension, you'll get instant feedback on the screen. Eventually you'll learn how control these functions on your own, without the biofeedback equipment.

Different types of biofeedback are used to monitor different body functions:

Electromyogram (EMG). This measures muscle activity and tension. It may be used for back pain, headaches, anxiety disorders, muscle retraining after injury, and incontinence.

Thermal. This measures skin temperature. It may be used for headache and Raynaud's disease.

Neurofeedback or electroencephalography (EEG). This measures brain waves. It may be used for attention deficit hyperactivity disorder (ADHD), epilepsy and other seizure disorders.

Electrodermal activity (EDA). This measures sweating and can be used for pain and anxiety.

Heart rate variability (HRA). This measures heart rate. It may be used for anxiety, asthma, chronic obstructive pulmonary disease (COPD), and irregular heartbeat.

Each biofeedback therapy section lasts about 30 minutes. Usually, you can start to see biofeedback benefits within 10 sessions or less. Some conditions, such as high blood pressure, can take 20 or more sessions to improve.