The hold-relax is the most common type of PNF stretch. Your muscle is held in a passive stretch for about 20 seconds. Then that same muscle is contracted in a stationary position and is not moved. This contraction is held for 10 to 15 seconds before you relax your muscle for 3 seconds. Repeat the passive stretch for 20 seconds. The contraction allows the muscle to be stretched further than before.
The contract-relax technique is very similar to the hold-relax technique. A passive stretch is held for 20 seconds and then contracted. The difference between the contract-relax and and the hold-relax is that in the contract-relax technique, the muscle is contracted concentrically. This means the muscle is moved so it temporarily shortened. The contraction is released for a couple of seconds and then the passive stretch is repeated for another 20 seconds.
Contract-Relax with Antagonist Contract
The contract-relax with antagonist contract method appears to be the most effective type of PNF stretch. In this stretch, the muscle is stretched for 20 seconds. It is then contracted concentrically, such as in the contract-relax. After holding the contraction for 10 seconds, the muscle opposite to the contracted muscle is contracted statically for 10 seconds as well. After a quick three second relax, the passive stretch is repeated.
Less Common Types of PNF Stretches
Advanced athletes will sometimes use the hold-relax-swing, also known as the hold-relax-bounce. The hold-relax-swing is exactly like the hold-relax technique, except the ending passive stretch is replaced with a ballistic stretch, which uses bouncing motion to further stretch the muscles. It is rarely done because it can be dangerous. Post facilitation stretching is another uncommon PNF technique wherein the stretch is started midway between a completely relaxed position and a maximally stretched position. The muscle is contracted with as much strength as possible and held for 10 seconds. The muscle is released and immediately re-stretched. Other types of PNF stretches include rhythmic initiation and rhythmic stabilization.