Which of the following is NOT an accurate flexibility exercise guideline?

- Choose flexibility exercises for all major muscle groups
- PNF and static stretching flexibility exercises are recommended for beginners
- No pain, no gain—feeling pain lets you know that you have overloaded the muscle with stretch
- Gradually increase the time you hold your stretches as well as the number of sets of stretches
- Avoid stretching muscles that are already overstretched from poor posture
- To get the most benefits from flexibility exercise, you need to warm up