Biofeedback is the use of instruments and devices to enable a person to monitor body responses triggered during the stress response such as heart rate, blood pressure, muscle tenseness, skin temperature, sweating and brain electrical activity. The technique allows the user to see for themselves their level of stress response activation and state of relaxation. Biofeedback is a useful tool for relaxation training, as it will indicate to the user whether or not a state of relaxation has been achieved.
One of the most commonly used methods involves measuring the amount of sweat on the skin. During the stress response sweating increases; in the relaxation response it decreases. The amount of sweat on the skin is detected by two small metal plates (electrodes), each strapped to a finger. A small safe electrical current is passed across the electrodes. When the skin is moist, due to the presence of sweat, the current passes easily over the skin. When the skin is drier, the passage of the current is impeded because the skin resistance is higher. So this technique measures the skin resistance and is known as the galvanic skin response or GSR. In fact, GSR techniques form the basis of lie detector apparatus. Usually when a person tells a lie, their emotions trigger the stress response, leading to sweating.
For biofeedback information, the skin resistance is converted into a sound. Increased stress and tension lead to a high-pitched sound, relaxation results in a lowering of the sound.
Skin resistance meters are relatively inexpensive devices suitable for self-help purposes. More sophisticated and expensive equipment is needed to obtain biofeedback from other body activities such as brain wave activity. However, a very simple and inexpensive device for self-help is the biodot. Available from Stresswise (see page 209).