I do not think anyone has a ready answer for your question.
For one, what do you think you are stretching ( nerve,muscle,joint, connective tissue, scars?) and in which cases?
I have just started reading Skeletal Muscle, structure, Function and Plasticity - the phsyiological basis of rehabilitation 3rd edition by Richard Leiber
( Lippincott Williams & Wilkins Home Page )
You will have to divide your question into either:
- age groups
- disorders
- acuut or chronic problems
- neurologocial damage yes/no
and then maybe you might find some information. I do not have any answers for you at the moment. I suggest you buy the above book.
kind regards
Esther