tensing your way to sleep
Progressive muscle relaxation asks you to deliberately tense a muscle before letting it go, which sounds like the opposite of what you want at bedtime. It's the oldest relaxation protocol in clinical use, it's the basis of the slow release track, and the counterintuitive bit is the bit that works.
why you tense first
Edmund Jacobson published progressive relaxation in 1938, and the core insight has survived nearly a century of people trying to improve on it.
Jacobson noticed that anxious patients could not relax on command. Told to relax a shoulder, they would report that it was relaxed, while it plainly wasn't. The problem was not unwillingness. It was that they had been holding that shoulder for so long that its held state had become the baseline, and you cannot release a tension you can no longer feel.
So he had them tense it first, hard, on purpose. Squeeze the muscle for five seconds, then let go. The contrast between the two states is what makes the release perceptible, and once it's perceptible it can be repeated. Tensing on purpose is not the exercise. It's the instrument that lets you find the exercise.
This is the part people skip when they try to shortcut the protocol, and skipping it is why the shortcut doesn't work. Lying in bed telling your jaw to unclench mostly produces a jaw that is still clenched, plus a new feeling of failing at relaxing.
you cannot let go of something you didn't know you were holding.
the run through the body
The full protocol works through the body in order, usually feet upward, one muscle group at a time. Tense for around five seconds. Release. Sit with the released feeling for fifteen or twenty seconds before moving on. That pause is not padding. It's where the actual relaxing happens, and rushing it turns the whole thing into a workout.
Feet, calves, thighs. Hands, forearms, upper arms. Stomach, chest, shoulders. Neck, jaw, the muscles around the eyes. The face at the end is worth waiting for: most people have no idea how much they are holding in the jaw and the space between the eyebrows until the moment they let it go.
Tense firmly, but not to the point of cramp or pain. This isn't a strength exercise and there's no benefit to straining. If you have an injury, skip that region rather than working around it.
The whole run takes ten to fifteen minutes. Many people are asleep before the recording gets to their shoulders, which is a slightly annoying feature of a protocol built to be finished.
what it's good for
The evidence here is better than most bedtime advice manages. A 2008 systematic review with meta-analysis, covering ten years of trials, found relaxation training to be a genuinely effective treatment for anxiety, with progressive muscle relaxation among the best-supported forms of it.
That matters at bedtime because a lot of what keeps people awake is not sleepiness failing to arrive, it's arousal refusing to leave. A body that has been braced all day does not stop being braced because the light went off. PMR gives that body something specific and physical to do, and it works on the tension directly rather than asking the mind to talk itself down, which the mind at 1am is notoriously bad at.
It is particularly good for people who say they cannot switch off, and who find that breathing exercises leave them lying there with nothing to hold on to. This gives them something to hold on to, and then it takes it away, on purpose, one muscle at a time.