Your body needs to sense how long your muscles are to understand their position to help them function more efficiently. They have tiny sensory organs called muscle spindles. These are the sensory nerves that tell how long are short the muscle is worth it is quickly stretched.
Muscles have pain receptors in the membranes that surround them as well as where blood vessels course in the muscle. Research published in 2010 sheds new light onto how pain is felt in relation to these muscle spindles. When the muscle is injured such as an overload or a sprain strain these pain receptors are activated. Damage to these filaments can contribute to chronic muscle pain.