The PNF techniques were first used by physical therapists for treating patients who had various types of neuromuscular paralysis. Only recently have PNF stretching exercises been used as a stretching technique for increasing flexibility.
There are a number of different PNF techniques currently being used for stretching, including slow - reversal - hold - relax, contract - relax, and hold - relax techniques. All involve some combination of alternating contraction and relaxation of both agonist and antagonist muscles (a 10 - second pushing phase followed by a 10 -second relaxing phase). Using a hamstring stretching technique as an example, the slow - reversal - hold – relax technique would be done as follows. With the athlete lying supine with the knee extended and the ankle flexed to 90 degrees, the athletic trainer passively flexes the hip joint to the point at which there is slight discomfort in the muscle. At this point the athlete begins pushing against the athletic trainer's resistance by contracting the hamstring muscle. After pushing for 10 seconds, the hamstring muscles are relaxed and the agonist quadriceps muscle is contracted while the athletic trainer applies passive pressure to further stretch the antagonist hamstrings. This should move the leg so that there is increased hip joint flexion. The relaxing phase lasts for 10 seconds, at which time the athlete pushes against the athletic trainer's resistance, beginning at this new joint angle. The push - relax sequence is repealed at least three times.
The contract - relax and hold - relax techniques are variations Ml the slow - reversal hold - relax method. In the contract - relax method, the hamstring are isotonically contracted so that the leg actually moves toward the floor during the push phase. The hold - relax method involves an isometric hamstring contraction against immovable resistance during the push phase. During the relax phase, both techniques involve relaxation of hamstrings and quadriceps while the hamstrings are passively stretched. This same basic PNF technique can be used to stretch any muscle in the body. The PNF stretching techniques are perhaps best performed with a partner, although they may also be done using a wall as resistance.
