Some terminology I use when discussing stretching and flexibility:

Full Range of Motion - this is exactly how for the human body can possibly move in any one direction. This will vary based upon sex and body type but little else affects it.

Functional Range of Motion - this is exactly how far the human body can possibly move in any one direction AT ANY GIVEN MOMENT IN TIME. This will vary based upon fitness level, age, current or past injuries, fatigue and mental attitude. This can never exceed full range of motion and usually is far less.

Flexibility Limit - this is the limit inside the individual's functional range of motion where the muscles involved can function normally. A simple example: the height where you can make a side kick and hold it there is your flexibility limit for a side kick.

Elasticity Limit: this is the region inside an individual's function range of motion but beyond the flexibility limit. In this range it is the ability of the muscle and connective tissue to stretch and rebound (be elastic) that allows you to make a kick or strike. Using our example, this is the height where you can "fire off' a side kick but you cannot hold it there. range, height and some power but little to no control.

Some concepts about flexibility using my terminology:

The ideal flexibility is when your full range of motion, functional range of motion, and flexibility limit are exactly the same. This should be your goal in flexibility training; there should never be any reason to "take a bounce".

You CANNOT increase your flexibility limit unless you perform your stretching routine beyond that limit and inside the elasticity limit.

Flexibility stretching MUST include both relaxation and strengthening actions in order to be effective.
- The individual must start at their flexibility limit and then push past that limit into the elasticity limit. When this happens the muscles will tense up and resist and you must wait (20-30 seconds) for the muscles to relax again before proceeding. This is what I mean by 'relaxation". Often one finds that there is more elastic range available after the muscles relax, and you can repeat this process a number of times before you actually hit the elasticity limit or the end of functional range of motion.

- When the individual reaches their elasticity limit, they must then strengthen the muscles at that range. This is done by tightening the muscles and pulling against the stretch. It is better to pull with about 1/3 to 1/2 of your strength than to pull as hard as possible, and this should be repeated 2-3 times with about a 20-30 second rest period in between.

- You eased into a stretch; ease out of it. Never just "let go". Take your time, muscles need to relax on the way out of the stretch just as much as they did getting into it, the 20-30 second rule applies here as well.

OKAY PEOPLE, LISTEN UP!!! THIS IS THE MOST INCREDIBLE LINE OF B/S EVER!

"IF YOU ARE STRETCHING AND YOU FEEL PAIN YOU ARE DOING IT WRONG"

I generally try not to get upset when I hear nonsense being repeated as gospel, or when I hear opinion being repeated as fact, or when I hear someone who HAS knowledge and understanding misspeak and therefore literally DESTROY the ability for another to advance in their training.

This is pure nonsense.