An interesting point about stretching ligaments vs muscle-tendons -
In the reference Stretching Scientifically
(2003), 4th Ed, T. Kurz distinguishes between muscle-tendon stretching and stretching the ligaments at a joint. [Ligaments connect bone to bone.] He says that stretches aimed at elongating ligaments for adults may lead to lose joints and be hazardous.........very interesting discussion. There are many insightful discussions and observations in this book that I have not seen in any other stretching references.
In another area of research - Over the last several years there is biomechanical research that indicates that the muscle-tendon-fascia combination may not be as important for elasticity as the basic muscle cell itself. As best I understand it when elasticity is measured on isolated muscle cells the same elastic properties can be observed in a single basic cell. That is, the muscle overall structure/facia/tendon may not be as important as has been thought. ( I'm not sure if there are serious controversies with the new conclusion. ?) A protein molecule in the muscle cell itself called Titin may play the main role in elasticity. See last paragraph on Titin- http://muscle.ucsd.edu/musintro/contractions.shtml