Here are some other general guidelines when completing PNF stretching: • 1. Leave 48 hours between PNF stretching routines. • 2. Perform only one exercise per muscle group in a session. • 3. For each muscle group complete 2-5 sets of the chosen exercise 4. Each set should consist of one stretch held for up to 30 seconds after the contracting phase. • 5. PNF stretching is not recommended for anyone under the age of 18. • 6. If PNF stretching is to be performed as a separate exercise session, a thorough warm up consisting of 5-10 minutes of light aerobic exercise and some dynamic Stretches must precede it.