Anytime an athlete is experiencing a sensation of muscle tightness, the first step taken should be assessing their joint mobility. Most of the time the root of the problem lies with joint mobility. For example, a common sensation cyclists experience is tightness in the hip flexors. Is this coming from hip flexors that are actually too tight or is a hypo-mobile joint restricting hip extension? Take it even a step farther, is the hip joint hyper-mobile and the hip flexors have increased tension in an effort to produce joint stability? The fact is very rarely is a tight hip flexor sensation coming from a tight hip flexor! To find the answer differential diagnosis is key to finding a solution and in both these situations, stretching is not the answer!
This idea of differential diagnosis must then be taken one step further. In the example of restricted hip extension, once the hip joint has been ruled out, we still aren't done. This only confirms the problem to be muscular, but fails to tell us which muscles are actually limiting extension range. Is it the one-joint hip flexor Iliacus, or the two-joint Rectus Femoris, or to complicate things even further is it the TFL, IT band, or the nervous system?
This "tight" feeling could be coming from the nervous system. However, due to its amazing complexity, it is often overlooked when talking about stretching. We need to respect the fact that manipulating the nervous system alone can yield massive improvement in muscle elongation abilities. In the presence of pain and pathology, extra care most certainly is warranted. However, even in a non-injury state, the nervous system must be evaluated effectively in order to understand its limitations and nature of response.