Proprioception: The Sixth Sense
Updated: Aug 2, 2021
Edited by Dr. Trevor Bennion
In elementary school, your science teacher probably taught the five senses: taste, touch, smell, and sight. What they did not teach you was the last two senses: balance (vestibular), and proprioception. Proprioception is your body’s spatial awareness, and most people refer to proprioceptive organs as reflexes. Close your eyes and move your arm around. You instinctively know where your arm is in relation to your body. These sense organs protect the body and, with knowledge, can be utilized to increase range of motion.
There are four proprioceptive organs: muscle spindles, Golgi tendon organs, Pacinian corpuscles, and Ruffini endings
Proprioception is you internal and external spatial awareness sense
Proprioception is used to keep the body safe by being an automatic reflex
Vocabulary Terms and Definitions:
Proprioceptors - Terminal end organs that almost instantaneously relay information about muscular dynamics and limb movement to conscious and subconscious portions of the central nervous system.
Muscle Spindles - Named for their similar shape to the spindle on a spinning wheel, muscle spindles provide mechano-sensory information about changes in muscle fiber length and tension.
Golgi Tendon Organs - Named after the Italian physician Camillo Golgi who first identified Golgi tendon organs in 1898, these fine-tuned sensory receptors detect differences in the tension generated by active muscle rather than muscle length.
Pacinian Corpuscles - Small, ellipsoidal bodies located close to the Golgi tendon organs and embedded in a single, unmyelinated nerve fiber. These sensitive sensory receptors respond to quick movement and deep pressure.
Ruffini Endings - Ruffini endings detect stretch, deformation within joints, and warmth.
Proprioceptive Neuromuscular Facilitation (PNF) - A type of stretching that was originally developed as part of a neuromuscular rehabilitation program, designed to relax muscles with increased tone or activity. It has since been expanded to athletics as a method of increasing flexibility. PNF techniques are usually performed with a partner and involve both passive movement and active muscle actions.
There are four proprioceptive organs: muscle spindles, Golgi tendon organs, Pacinian corpuscles, and Ruffini endings. Muscle spindles reside within the belly of a muscle. These sense the stretch of a muscle (Tuthill & Azim, 2018). If this organ is triggered it causes the muscle belly to contract (Tuthill & Azim, 2018). Golgi tendon organs reside within the tendon near the bone (Tuthill & Azim, 2018). They sense the amount of contraction within a muscle (Tuthill & Azim, 2018). If the Golgi tendon organ is triggered it causes the muscle that it’s attached to, to relax (Tuthill & Azim, 2018). The Pacinian corpuscles and Ruffini endings reside in the joint. Pacinian corpuscles sense the increasing or decreasing angle of the joint while it is moving and Ruffini endings sense static joint positions (Tuthill & Azim, 2018).
For our nervous system to receive signals, the message must travel all the way up the spinal cord to the switchboard of the nervous system: The thalamus. From the thalamus, the message is relayed to the cortex of the brain. This process is not necessary for proprioceptive organs. Instead, for proprioceptive organs, the nerves send the impulse to the same level of the spinal cord then the impulse gets sent right back to the muscle (Tuthill & Azim, 2018). It is why the response is automatic; it does not need the central nervous system to give it instructions. The information does eventually get to the cortex of the brain to process what happened, but by then the reaction has already occurred. Because these responses are involuntary it allows for a quick response. Our body needs to protect itself as quickly as possible which needs to happen faster than the time it takes to think.
The Muscle spindles are protecting against the muscle being strained through too much stretch and the Golgi tendon organs are protecting from the muscle tendon pulling away from the bone in an avulsion fracture (Tuthill & Azim, 2018). When you are falling asleep, while sitting up straight, and your head begins to fall forward you are suddenly woken up by a snapping back of your head into place. That is the myotatic reflex of the muscle spindles.
You may have heard the term Proprioceptive Neuromuscular Facilitation or PNF before if working with a trainer or physical therapist. PNF is a stretching technique that uses the reflex of the organs to help increase range of motion. This technique uses the myotatic reflex of the muscle spindles and the autogenic inhibition reflex of the Golgi tendon organs to cause a deeper relaxation of the muscle you are trying to stretch. If you have ever tried carrying something extremely heavy and felt, for no reason, you were about to drop it, it could be due to the Golgi Tendon Organs sensing the extreme contraction of the muscle and then telling the muscle to relax.
Proprioception is critical for balance, internal and external spatial awareness. It also can be utilized to increase range of motion.
For more information on PNF and other stretching techniques please join us for our 10 week coaching course where we dive into the nitty gritty of stretching.
References:
Han, J., Waddington, G., Adams, R., Anson, J., & Liu, Y. (2016). Assessing proprioception: A critical review of methods. Journal of Sport and Health Science, 80-90.
Tuthill, J. C., & Azim, E. (2018). Proprioception. Current Biology, 194-203.