PNF Stretching
PNF stands for Proprioceptive Neuromusclar Facilitation, so no suprise as to why we abbreviate!
This form of stretching is known to be the most effective for increasing flexibility in the muscle and increasing range of movement in the  joint..however it is not always easy to carry out...you do need a partner..you need someone who knows what they are doing and you need some extra time.
The main form of stretching Lazy Runners use is static stretching..this is where you hold the muscle in a stretched position for about 30 seconds, relax and repeat.

PNF stretches involves taking the muscle or joint into a static stretch for about 30seconds, then contracting that muscle and using force to resist the stretch (that's where the partner comes in) for 8 seconds, then a brief rest and then the muscle is put back into the same static stretch for another 30seconds, this time the stretch should be greater.

All this is repeated 3 times on each muscle. It is very effective if performed on the larger muscles or muscle groups such as the hamstrings, the glutes, hip flexors and the adductors (inner thigh muscles).PNF stretching is also not recommended for children and people whose bones are still growing .

 PNF stretching helps strengthen the muscles that are contracted and therefore is good for increasing active flexibility as well as passive flexibility. PNF stretching should not be performed daily as the muscles need time to gain the full benefits of the procedure, once a week is enough.