Proprioception is the internal regulatory system of the body that governs the ability to generate and maintain an effective upright posture and physical balance. An internal sensory feedback system, proprioception is the complex series of communications that signal a variation in muscle contraction made in response to any external factors. The important proprioceptors located within the body are the vestibular system (the organs and nerves of the inner ear) and the stretch receptors, nervous system components that are located in the muscles of the joints. These receptors assist in permitting the body to know where the joints are positioned at any time. A prominent stretch receptor, the Golgi tendon organ, is located at the junction of various tendons and corresponding skeletal muscle, relaying the degree of muscle tension present at any time to the brain.
Proprioception and its importance to human movement is best understood in contrast to two other sensory concepts, the first of which is the physical senses. The five senses of taste, touch, smell, sight, and sound are all sensory devices that act as both a monitoring system and as an early warning defense for the body in relation to its environment; information is received by each sensory organ and transmitted to the brain for processing and, where required, action. In contrast, proprioception is the method by which the body regulates itself, both in terms of physical position, as well as orientation to the ground or other fixed objects.
The second contrasting concept to that of proprioception is that of the human kinesthetic senses, the related notions of muscle memory and hand-eye coordination. The kinesthetic sense is similar to proprioception, in that it is an internal mechanism, but distinct by virtue of the role of proprioception in coordinating joint motion and acceleration.
Proprioception has been referred to as the "sixth sense," as it will continue to function in the event the physical senses cannot function. A common feature of cases involving an amputation is the sensation on the part of the amputee that the absent limb is producing pain.
The vestibular system of the inner ear is a delicate bone and tissue structure that coordinates balance, orientation, and the detection of acceleration in objects near the body. The inner ear can recognize changes in each of these physical areas more quickly than the coordinated efforts of the eye (through the optic nerve) and the brain. There are two primary sub-mechanisms within the inner ear that provide data for proprioception. The cilia are very fine hairs located along the inner ear canal. These structures sense changes in acceleration, transmitted to the brain by way of the vestibular nerve.
The function of the vestibular system is prominent whenever an athlete is endeavoring to track an object that has been sent into the air on a trajectory, such as a fly ball in baseball or a rugby ball kicked down the field. The vestibular system provides continual input regarding speed and body orientation to the ground as the player closes in on the ball.
In addition to sports where an object must be followed in the air, airborne sports, in which the athlete's physical equilibrium are distorted through the movements required by the sport itself, are those where proprioception skills must be developed to their fullest extent. Diving, gymnastics, and aerial
Balance has components that are genetically based. As a very general proposition, smaller people tend to possess better balance skills and the related features of physical coordination than do larger people, by virtue of the physiological fact that the smaller person is required to control a smaller mass, with a smaller neuromuscular system to be managed. Further, when persons of any size have structural imbalances, such as leg length discrepancies, which create unequal generation of forces in movement, it is likely that such persons will be less coordinated and less balanced in their movements.
Balance training is intended to complement the proprioception system. The first and most important aspect of balance training is the building and maintenance of the core strength of the athlete. A maximum level of core strength, the integrated efforts of the abdominal, gluteal, lumbar, and groin muscles and connective tissues, permits the athlete to incorporate stability into every movement in sport. A well-developed core strength also permits a stable and maintained athletic stance, the couched playing position with knees and hips flexed, head erect, that is at the heart of numerous sports.
Once core strength is in place, the athlete can develop a series of physical attributes that contribute to quickness, performed on a stable physical platform. The ability to transfer weight effectively and seamlessly is a hallmark of athletic balance. Exercises that place the athlete in a continuous series of constant and dynamic movements reinforce for the body its proprioception system.
Any exercise that requires the body to respond instantly to physical position will aid in balance training. Activities as varied as juggling and the use of a wobble board (a device where the athlete is positioned at the center of the board to maintain balance) are employed to perfect balance.