I've heard many of my clients saying, "I have no flexibility. I am made of wood. I am too old to increase my flexibility.." I've been thinking about this and had a chance to organize my thoughts around it. It is a bit long post but definitely have some information that you might like to hear about. So brace yourself :) It is also related to foam rolling or other self-myofascial release technique that lately became the new norm for mobility training.
While it is true that there are individual differences in flexibility and that aging can contribute to decreased flexibility, we are actually more flexible than we think. The founder of Functional Range Conditioning, Dr. Andreo Spina, beautifully explained how we are more mobile than our perceived flexibility limit. According to him, our nervous system (or brain) automatically sets the safe range of motion that is smaller than actual range of motion that we are physically capable of using. A good example of this is that we can usually perform a straight leg raise much further when a therapist push the leg for us compared to when we try to do it by ourselves. Our body usually protects us from going beyond the safe range of motion virtually set by the nervous system, because we haven't gained ability to stabilize the joint as we go beyond that range of motion. This indicates that we are not structurally stuck at the current range of motion, thus our joint mobility will improve as we explore or regain control over the virtual safe range of motion. There are different ways to regain that control. Controlled functional range conditioning shown below can be one of the examples (for the details visit https://youtu.be/nLuvQCTPrcY).
As we try to explore larger range of motion, we have to learn how to deal with the brain's way of preventing us from going beyond the virtual safe range of motion. The brain tends to elicit a pain response that results in shortening of the muscle when we try to stretch the muscles. What triggers such pain response is the tension we receive in the muscles and connective tissues when we try to mechanically lengthen the muscle. Often, that pain threshold is unnecessarily low and can even make our dynamic stretching counterproductive as the reflexive contraction of the muscles can overly stress our connective tissues like tendons.
Foam rolling (or any type of self myofascial release) before dynamic mobility training can help our muscles to be more relaxed by temporarily increasing the pain threshold; meaning that the body can now tolerate more stretching-related tension before it generates protective contraction of the muscles. Foam rolling gives you gentle pain as you put continuous pressure on the tender spot or trigger point. Continuously feeding our brain with this so called "good pain" eventually help our nervous system relaxes the boundary of protective response during stretching, because the brain recognize that, "yes, there is a pain but it is not necessarily dangerous so I don't have to be overly protective about it." This concept is well explained as the theory of "Diffuse Noxious Inhibitory Control (DNIC)" DNIC is better explained by a movement expert, Todd Hargrove in this link. A fellow Kinesiologist and a good friend of mine, Jordan Smith, described this process in a genius way: "the 'candy' pain is safe for our neuro-immune system." In addition, David Butler from the Neuro Orthopedic Institute explained that DNIC can reflect our context dependent pain modulation (visit https://youtu.be/Gd2NaGZa7M4 for details).
Remember that the key to the successful foam rolling is the "good" pain. Don't be to gung-ho and put too much pressure until you get bruise, this can actually make the brain narrow its protective boundary.