METs utilize voluntary contraction of the muscle against a counterforce to mobilize joints and lengthen shortened muscles. Robert Daul, MPT explains the precise treatment:

Following a 3-5 second contraction, the operator takes the joint to its new barrier where the patient again performs a muscle contraction. This may be repeated two or more times. This technique is considered an active procedure as opposed to a passive procedure where the operator does all the work (such as joint mobilizations). Muscle energy techniques are generally tolerated well by the patient and do not stress the joint.