Have you ever wondered about your ability to sense movement?
Your ability to know where you are in space? The unconscious perception of movement and the ability to know where you are spatially with orientation to other objects against gravity arises from the stimuli and the receptors within the body itself. Every precise, coordinated movement requires precise proprioception at work.
Proprioception means “sense of self”. In the limbs, the proprioceptors are sensors that provide information about joint angle, muscle length, and tension, which is integrated to give information about the position of the limbs in space.
Sensory Receptors: We also have other receptors that give us feedback like the eyes and ears which have the visual receptors and the vestibular receptors help us when doing complex movements.
Have you ever wondered how you could walk downstairs in a dark room and not fall down the stairs? How someone can move beautifully like a dancer or doing complex movements like balancing on a beam or tightrope?
Where does proprioception come from? In the body there are free nerve endings and receptors that are located in our ligaments, skin, muscles, joint capsules, and tendons. These tiny receptors include over 17,000 skin receptors in a piece of 1 cm of skin alone! We have millions of these receptors located in our bodies.
These receptors then feed into the higher brain centers of the central nervous system and in turn relay information to the brain to both the cerebrum, (which is the higher brain) for processing, and the cerebellum, the small, golf ball like part of the brain at the brainstem.
Other receptors include information from the eyes and the ears that allow us to coordinate hand, foot and eye coordination, and also balance. Proprioceptive training, also known as neuromuscular training, involves the integration of proprioceptors, specifically the Ruffinis endings, Pacinian corpuscles, Golgi Mazzoni corpuscles, Golgi-tendon organs, Golgi-ligament endings, and muscle spindles.
Any successful rehabilitation program must include activities that address “training of the prorioceptors”. By doing these types of activities, the athlete or individual also improves their kinesthetic awareness and confidence with complex, skilled movements. Take for example, expert high-speed snowboarding. This requires fast, reflexive movement and a reactive, fully functioning nervous system. To be an expert snowboarder, you have to be able to make sense of the position of your limbs relative to your center of gravity (over the base of support), while also positioning your body against the earth’s surface and gravity, interacting with the board and the snow. Your visual and vestibular (inner ear) system is constantly orienting you to your sense of position, as well. This is all happening automatically, coordinating activity with thousands of sensory stimuli coming into the nervous system via the sensory receptors.
These receptors can be stimulated and trained and are the basis of many of our training programs including injuries to the foot and ankle, injuries to the knee, hip or spine in rehabilitation and athletes who want to perform efficiently.
Proprioceptive training includes the ability to hop, jump, cut, change directions, and balance on one leg on unstable services. The greatest number of proprioceptors occur in the ankle and the soles of the feet. These are cutaneous (skin) receptors. There’s also a number of them at the base of the skull located in the muscles called the suboccipital muscles. They act as a gyroscope to let us know where we are in space and orient us with gravity and the horizon.
How do they get injured or altered? When there is an injury and there is pain, the body undergoes a protective response by decreasing muscle activation and altered proprioception. Poor proprioception can be altered in the injured and also as we age, particularly with the elderly. As we injure ourselves and damage to the tissue occurs, the pain mechanisms that feed into our brains tend to override the nerve cells transmissions to the brain and we don’t have such a defined appreciation for positional sense. This basically slows the neurological system down. These delays or deficits can be assessed with movement testing by a clinician.
There are some anatomical structures that play essential roles in proprioception. For example, the ACL or anterior cruciate ligament, has numerous nerve endings that contribute to proprioception along with the lateral ankle ligaments; the most commonly injured is the anterior talofibular ligament. This ligament can be injured in an inversion ankle sprain or when the foot and ankle turn in. Injury to these ligament structures will make us feel unstable. The athlete may sense a feeling of being unconfident or unsteady on uneven surfaces.
We also observe these proprioceptive deficits in the aging population. The elderly have aging nerve endings and their nerves may not conduct the information as effectively as younger people. They have more trouble with activities requiring body awareness and as a result can fall easily. The nervous system needs stimuli to adapt, and by training, this can be improved and is the basis of many balance programs for the elderly.
Many research studies confirm that proprioception and fall programs are essential for prevention of injuries; we place a big emphasis on this in our work as physical therapists and athletic trainers.
Check back soon for Part 2, which will deomonstrate some proprioceptive training exercises.