Mechanoreceptors are little sensors that alert the body if there are and what kind of imbalances may be present. They are made up of spindles and Golgi tendon organs. The spindles keep the muscle in check and don’t let it stretch too fast. When the muscle is stretched the spindle sends the signal through the feeling of tightness. Exciting the Golgi tendon organ sends the signal for the muscle to contract. In order to increase efficiency and flexibility working past this signal safely is ideal.
If the body is moving properly in all ranges of motion it is therefore efficient and has benefited through the practice of flexibility.