Much of the soft tissue of the human body can be described as plastic, elastic, or some combination of the two depending on the strain. Knowing which elements have which properties and how best to train them can be important knowledge for a coach to have. Elastic tissue is similar to a rubber band. Stretch it and it will snap back. When we speak of the elastic tissues of the body we’re primarily concerned with the tendons. Plastic tissue doesn’t have that same recoil. If it’s stretched too far it will remain stretched and have a permanent deformation. Cartilage and to a lesser extent fascia is generally thought to be plastic in nature.
Efficient movement requires sufficient mobility in all tissues to permit adequate range of motion at a joint while still being able to take full advantage of the elastic properties of tendons and muscles. Very few people have the perfect balance which makes addressing the different structures (and there associated ranges of motion) very important to truly maximize performance. In fact, many excessively asymmetrical movements or inefficient movement patterns can be addressed through diligent mobility work. Unfortunately, in cases like these, traditional static stretching will not suffice. Because we’re looking for plastic deformation of restricted areas the tension has to either be quite high during extreme ranges of motion and / or for extended periods of time. If neither of these is observed any stretching will be primarily for CNS down-regulation and social time and not making lasting changes in the tissue. The trick is that this needs to be done without causing laxity or reducing any of the beneficial elastic properties of the joint. This is where an understanding of functional anatomy really helps. For a quick primer, I suggest picking up The Concise Book of Muscles, Revised Edition