This is just something that are a collection of thoughts based on what I've seen and read, right of wrong this is my thoughts on flexibility as a result of exercise.
And I'm not trying to sell anything and I have a little time this morning.
Exercise should increase flexibility...but it seldom does.
Proper full-range exercise will increase flexibility, but improper, mid range exercise may have an opposite effect.
Contrary to popular opinion the size of your muscle has absolutely nothing to do with your flexibility...but the method you use to biuld those muscles is important.
Distance runners normally have very little in the way of muscular size, so you expect them to be very flexible, but in fact quite the opposite is true, injuries are common among these blokes and are mostly a direct result of their in-flexibility.
In contrast, gymnasts are very muscular and very flexible.
So it should be clear that there is no relationship between muscular size and flexibility.
Flexibility is a result of stretching.
So exercises that involve stretching will increase flexibility....while exercises that do not involve stretching will not increase flexibility, will not, in fact, and this is interesting, even prevent a gradual loss of flexibility, may even produce a loss of flexibility.
Where possible exercises should involve stretching...but in practice, very few exercises do involve stretching.
In order to provide stretching, the range of movement of the exercise must actually exceed the possible range of movement.
*In effect, you must reach your limit of movement and still encounter resistance*
If it is possible to relax in the extended posisition of an exercise and remove the resistance, then stretching is not provided.
The bench press does not provides stretching... Because, at the bottom or the movement the wieght is supported by the chest
In contrast, a prperly performed dip exercise does provide stretching for the chest and shoulder muscles....because, in the low position, the resistance is not removed.
Regardless of your exciting level of flexibility, the resistance will still be imposed even when you have reached the limit of the movement.
And I said properly performed exercise.
It is also possible to perform the exercise incorrectly and it is usually performed incorrectly, and if so, then stretching is still not provided, I can give examples of this and examples of exercises that do and do not provide stretching.