Muscle Energy Technique (MET) and Proprioceptive Neuromuscular Facilitation (PNF) both use your own contractions to get a muscle to let go — taking advantage of the fact that a muscle relaxes more readily immediately after it has contracted.
What you actually do
You will be asked to push against my resistance at a controlled effort — often quite gently — hold for a few seconds, then relax. The limb is then taken into its new range. Repeated a few times, range typically improves noticeably within a session.
Why use it
It is active rather than passive, so it tends to hold better than stretching alone. It is comfortable, which makes it suitable where tissue is too sensitive for deep work. And because you are contracting the muscle, it starts rebuilding control through the new range rather than just creating slack.
Who it suits
Anyone whose range of movement is restricted but whose tissue is too sensitive, too acute or too guarded for deep work. Because you control the effort, it is comfortable and it is easy to stop — which makes it a good first technique on a nervous client, a recent injury, or an area that has been painful long enough that the muscles brace before anything even touches them.
It also suits people who want to be doing something rather than lying there.
What it is not
It is not passive stretching, and it is not the therapist forcing a limb further than it wants to go. The contraction is yours, usually at somewhere between a quarter and half of full effort — pushing as hard as you can is counterproductive and a common mistake.
What to expect
Range usually improves within the session, often noticeably. Holding it is the harder part: new range that is never used gets given back within a couple of weeks, so it is paired with exercises that load the muscle through the range you have just gained.
There is rarely much soreness afterwards, which is one of its advantages — useful mid-season, or the week of an event, when deep work would leave you sore at the wrong moment. It pairs well with joint mobilisations where both the muscle and the joint have stiffened up.