biofeedback

It is surprisingly hard to know whether you are actually using the right muscle, or relaxing one you mean to relax — the body's internal signals are usually invisible to us. Biofeedback solves this by turning an unseen body signal into something you can see or hear in real time, so you can learn to control it.

A sensor picks up a body signal and a machine displays it as a line on a screen, a number, or a tone that rises and falls. The most common rehabilitation form uses surface electromyography (EMG), which detects the tiny electrical activity of a muscle: when you contract harder, the tone goes higher; when you relax, it drops. With this instant feedback a person can learn to switch a weak muscle on, to relax a muscle stuck in tension, or to retrain a coordinated movement. Other forms feed back heart rate, breathing, skin temperature, or pressure (for example to retrain pelvic floor muscles or to relax a tense jaw or shoulders).

Biofeedback is essentially a teaching tool, not a passive treatment that 'does' something to you — the work is the patient learning, with the machine as a coach. It is most valuable where a person genuinely cannot sense what a muscle is doing, such as after a stroke, with pelvic floor problems, with tension headaches, or in chronic muscle tension. Its limit is that the new skill must transfer to real life away from the machine; the goal is to need the feedback less over time, not to depend on the screen.