The body's ability to maintain an upright posture over a relatively small base of support (our feet) is a fascinating and complicated system of checks, and well, balances. There are three main sensory systems by which our brain detects our balance status; the vestibular system, proprioceptive (position detectors), and vision.

Balance: The Sixth Sense
Proprioception, the sense of your body's position in space (without looking) is mediated through nerves in your muscles that carry information back to the parts of the brain involved in planning and coordinating movement. Extend your arms in front of you, close your eyes, and then touch your nose with one of your index fingers. You should have been able to touch your nose without punching yourself in the face. This is proprioception.  This mechanism sends a message through your central nervous system for analysis. The information is then relayed to the rest of the body about how to react and with what amount of tension.

The vestibular system is a labyrinth of fluid filled canals in the skull that sense fluid perturbations that the brain interprets as movement. Spinning in place causes you to be dizzy even after you stop moving because this fluid continues to move inside the canals, confusing the signals to your brain. Finally vision, intuitively, enables you to plan your movement relative to the physical space around you.

The Dynamic Nature of Balance Through Life
Our sense of balance evolves and changes at different points in our life. Children learning to sit up and walk primarily rely on their vestibular and proprioceptive systems to maintain their balance. Of note, children of this age tend to have perfect posture, posture and gait being linked intimately with balance. For reasons that are not completely understood, possibly increased awareness of social interactions, children begin to rely more heavily on their vision for orientation between the ages of 4-6. This trend continues into adulthood, where some adults and seniors rely primarily on their vision. This is adequate in most situations, unless the person finds themselves with in situations where they are walking through a dark room, have deteriorating vision, or cannot find their glasses.

What most people fail to realize is that proprioception can be improved through training. In fact, many athletes, dancers, and practitioners of yoga regularly "exercise" their ability to sense their body's perception of balance increasing coordination, stability, and grace of movement. Rehabilitation and training exercises focus on developing the ability to sense imbalance without relying on vision, identifying muscular weakness, and teaching people to use the three main balance strategies that the body employs to correct imbalances after they have been detected by our sensory systems. These include the Ankle, Hip, and Step strategies.

How Do We Maintain Balance
The body can be viewed as an inverted pyramid with the ankles as the focal point of support. During a mild balance threat, internal and external somatosensory input recruits the ankles to correct and maintain balance through a gentle sway. The ankle strategy is a sub-conscious and an ongoing static response for maintaining and recovering balance. Close your eyes and stand with your feet close together and you should feel the sway that is your ankles maintaining your balance.

When the intensity of imbalance is increased, the ankles become overwhelmed, and the hips take over to recover balance. The ankle strategy still plays a role, but now, the body adds activation of the upper and lower limbs to adjust the body's center of gravity, contraction of the upper body muscles and core muscles for stabilization, and movement and bending in the hips to recover balance.

When violent disruption of balance over-powers the ankle and hip strategies, the step strategy is called upon as a last resort to prevent falling. The sensory systems send signals to indicate the need to re-position our base of support (i.e. the feet). We do this by stepping forward, backward or to the side until an adequate base of support is achieved.

When Balance Fails
A balance disorder is a disturbance that causes an individual to feel unsteady, dizzy, woozy, or have a sensation of movement, spinning, or floating. An organ in our inner ear, the labyrinth, is an important part of our vestibular (balance) system. The labyrinth interacts with other systems in the body, such as the visual (eyes) and skeletal (bones and joints) systems, to maintain the body's position. These systems, along with the brain and the nervous system, can be the source of balance problems.

When balance sensory and adjustment systems fail the sequelae can be dangerous; instability, anxiety, falls, injury, and in some cases death. Instability in our population has become such a problem that in 2003 Congress issued the Elder Fall Prevention Act instating education and research programs aimed at reducing the incidence of falls in one our most vulnerable populations; the elderly. Balance training also benefits people of all ages as it has been shown to reduce the incidence of injuries to the ankle, knee, hips, back and upper body. The role of balance training in maintaining functional joints stability is also an excellent form of rehabilitation for injuries to the body.