Therapists have used active inhibition techniques, most of which have been adapted from proprioceptive neuromuscular facilitation (PNF) techniques, for many years as an adjunct or alternative to manual passive stretching. Inhibition techniques increase muscle length by relaxing and elongating the contractile components of muscle. The assumption is that sarcomere give will occur more easily when the muscle is relaxed, with less active resistance (tension) in the muscle as it is elongated. An advantage of inhibition techniques is that muscle elongation is a more comfortable form of stretching than traditional high-intensity short-duration passive stretching. A disadvantage of active inhibition is that because it is a high-intensity stretch, it affects primarily the elastic structures of muscle and produces less permanent increase in soft tissue extensibility than more prolonged stretching methods.