Biofeedback techniques allow people to control bodily processes that normally happen involuntarily—such as heart rate, blood pressure, muscle tension, and skin temperature—in order to improve conditions including high blood pressure, headaches, and chronic pain. Patients work with a biofeedback therapist to learn these relaxation techniques and mental exercises. In initial sessions, electrodes are attached to the skin to measure bodily states, but eventually the techniques can be practiced without a therapist or equipment. Researchers still aren’t sure how or why biofeedback works—but a lot of research suggests it does work. Relaxation seems to be a key component, as most people who benefit from the practice have conditions that are caused or exacerbated by stress.