The vestibular system itself has multiple components that contribute to the sense of our position in space and the movement of the head in relation to the body. These include the semicircular canals and the organs that reside within our inner ear. The semicircular canals include three different structures that are oriented in three different planes, anteriorly, horizontally, and posteriorly. These are paired between the left and right side in such a way that both sides will provide the same information to the brain no matter the position that the head is in.
Next to the semicircular canals are the utricle and saccule. These sensory organs also help to provide information on the position of our head in space, but are more interested in acceleration both vertically and horizontally. Inside these organs are small crystals or otoliths that are embedded in the cellular membranes. Since these otoliths are a bit denser than the surrounding tissues and fluids, they are acted on by gravity more powerfully. When our head moves quickly or changes speed in general, these pressures in the utricle and saccule create electrical signals for the brain to interpret and coordinate.
Visual system :
We rely on our vision a great deal when it comes to orienting ourselves in space and with our environment. The eyes provide a wealth of information about where we are, how we are moving, and allows us to keep track of all of the elements in an ever-changing environment. The visual system has a very close relationship to the vestibular system and the brain/brain stem. In fact, there are a series of reflexes that exist within the brain that allow our eyes to hold steady in difficult circumstances, such as reading in a bouncing car, or being able to follow objects even as we change the orientation of our head such as watching a plane fly overhead. These reflexes rely on the ability of the brain and vestibular system to agree very closely on the position of the head and the necessary eye movement to keep everything in focus.
If there are any discrepancies in this communication it can lead to a feeling of slowness, eye fatigue, and accompanying dizziness and disequilibrium. There is a constant rechecking going on that makes sure that what the eyes are seeing and the vestibular system are reporting match up. What this means is that any compromise to vision or even changes in lighting can affect this communication and relationship.
Muscle and Joints:
The muscular system and proprioception are another key component of balance. The feet act as our contact point to the environment when we are standing or walking. The feet themselves are quite sensitive and good at measuring both pressure and force in a fine-tuned manner. I like to think of it as the steering wheel on the highway, it never holds perfectly still even when the road is straight and the constant adjustments and small twitches are what keeps everything in place in a dynamic fashion.
The information from the feet and ankles is sent to the brain to provide a sense of how our body is oriented. When walking on an incline or a decline this can get more complicated, with more muscle activity and more information being sent to the brain. If this information conflicts with the information from the vestibular or visual systems there can be confusion in the processing in the brain and a lack of ability to adapt to the environment (such as missing a step or stumbling/staggering).
All of these fine-tuned movements and measurements happening in the body allow for a number of places where things can break down. Sometimes, this system alone can lead to balance difficulties as inaccurate information from the feet, ankles, joints, and muscles can lead the brain to make poor decisions based on faulty information. Even in people who are experiencing primarily vestibular dysfunction it is often necessary to train the muscles of the lower extremities to develop control, strength, and power. The strength and power are often overlooked, particularly in an older population, but it is vital that the muscles of the foot and ankle be able to make the adjustments needed to maintain balance.
What can happen in some situations is that the brain will recognize an adjustment needs to be made, perhaps in a more challenging environment, but the ankles and feet are not powerful enough to make the necessary correction. This can lead to stumble, stagger, or fall, depending on the situation. Beyond the feet and legs themselves there is also the consideration of the core musculature that holds our spine and hips stable while moving or statically positioned. These muscles and the general control of this area from a proprioceptive perspective can greatly affect the control of our bodies and provide other strategies for maintaining balance outside of the ankle. While the ankle is the first line of defence for the average challenge to our balance, the hips and lower back can create changes in the center of gravity.
In an ideal situation, a small challenge to our balance would rely largely on the ankles and their respective muscles to adjust. However, if the challenge is large or fast, the hips can shift to absorb some of the force and to significantly alter the center of gravity. If the movement of the hips themselves is not enough, leaning the trunk/torso by utilizing the core musculature can also be implemented to regain or maintain equilibrium.
All of this is happening in a fraction of a second and is typically coordinated by the brain without much conscious effort. That being said, it is possible to train these responses and these systems. Much like any skill, progressive practice and repetition with guidance from a skilled practitioner can typically provide improvement in strategies and functional outcomes.
- Vestibular Rehabilitation: 4th Edition. Herdman, Susan. Clendaniel, Richard. ISBN 9780803640818. F.A. Davis. July 2014.
- Current concepts and future approaches to vestibular rehabilitation. Tjernstrom, F., Zur, O., Jahn, K. J Neurol 2016. DOI 10.1007/s00415-015-7914-1.
- Effects of balance training on balance performance in healthy older adults: a systematic review and meta-analysis. Lesinski M., et al. Sports Med 2015. DOI 10.1007/s40279-015-0375-y.