Recently, the abstract of a new study appeared on pubmed.org under the search term “whole body vibration”. What was unique about this study was that it didn’t involve a whole body vibration platform, but rather a device called a Vibrosphere which works much differently. The Vibrosphere is a disk shaped device that serves as an unstable surface for the purposes of balance and stability training. There are many devices available that are similar to the Vibrosphere, including wobble boards, dynadiscs, and bosu balls, but what makes this device unique is that it has the ability to vibrate at high frequencies. In this particular study, the vibration created an additional benefit for the subjects involved. The parameters that were improved in these individuals were trunk stability, postural control, and muscle tone.
In reviewing this study, and adding it to the multiple studies already published on the subject of the effects of vibration training on balance and stability, it is evident that the sensory component of vibration, perhaps regardless of the frequency, amplitude, or the resulting acceleration, may be all that is needed to enhance one’s balance and stability.
So how does the sensory input from a vibrating device actually influence the balance system of the human body? In the body, balance is a reflection of three key components. These include:
1) The Proprioceptive System (within the skin, ligaments, muscles, and tendons)
2) The Vestibular system (located in the inner ear),
3) The Visual system.
When it comes to vibration training however, it is the first component, the proprioceptive system, which is of most significance. The proprioceptive system is responsible for what we refer to as “proprioception”; more commonly referred to as “body awareness”. An example of an individual with excellent proprioception would be a ballet dancer. By definition, proprioception is “the sense of the relative position of the neighboring parts of the body”. The better the proprioception that we possess, the more accurate our movements are and the better we are able to respond to changes in the position of our bodies during movement (i.e. falling backward or forward, balancing on one leg, walking on a rough surface etc.).
Anatomically, the proprioceptive system is a complex matrix of sensory neurons, referred to as mechanoreceptors, located throughout the body. In our discussion here it is the mechanoreceptors located within and around the joints and muscles that we are most interested in. Mechanoreceptors are responsible for sending information to the brain regarding the various mechanical sensations that our bodies experience during our day-to-day activities or during exercise. Among the sensations picked up by mechanoreceptors during vibration training are pressure (in the form of compression), stretch (tension), and motion (lengthening and/or shortening of tissue). These sensations are also experienced to a lesser extent during everyday activities such as walking, climbing stairs, and running. This is why training repeatedly with superimposed vibration causes the mechanoreceptors to become more finely tuned. This leads to a more precise response from the central nervous system and a resulting increase in the precision and efficiency of our movements. This “learning response” represents the concept of neuroplasticity; the process by which the brain learns on a cellular level. In the words of Donald O. Hebb, “neurons that fire together, wire together” therefore improving the efficiency of their communication.
To go into the details of how receptors communicate with the brain is a conversation reserved for neurophysiologists. So for the purposes of simplifying it for this article, when information is received by a mechanoreceptor, that information is sent to the spinal cord via the peripheral nerves and carried through the spinal cord along specific tracts to the brain. The brain’s response to this information can occur on many levels. For example, it can reduce activity of a muscle (relax it), cause a muscle to contract (tense it), or decrease/increase the sensitivity of the receptors to further sensory feedback (mute or dampen it). In the case of a sedentary individual, the reduced sensory input, a reflection of less physical activity, causes the brain to decrease the sensitivity of the mechanoreceptors. This therefore reduces the individual’s precision and speed of movement in response to an unstable surface. As a result, the risk of falling increases for this individual. Combine this with the increased predisposition to osteoporosis among the same population and you can understand why fractures rank among the highest reported injuries in the elderly population. In another example, an athlete with poor mechanoreceptor sensitivity will respond ineffectively to the rapid joint movements, heavy muscular tensions, and repeated connective tissue stretching that they are exposed to during sport. This inevitably leads to tissue damage, pain, and inflammation and is the primary mechanism behind most overuse injuries seen in athletes today.
Still want evidence that these pathways exist? In another study published in the Journal of Sports Medicine and Physical Fitness, a vibrating upper body dumbbell created by the same company that created the Galileo vibration platform was used to assess the influence of vibration on electrical activity in the brain. The electrical activity was monitored using a technique referred to as transcranial magnetic stimulation (TMS). To simplify the results of the study and the conclusions drawn from the results, the vibrating dumbbell, in contrast to a non-vibrating dumbbell, demonstrated the ability to increase excitability of the motor cortex. This phenomenon therefore lends direct support to the idea that vibration, through the mechanoreceptor pathways, can directly stimulate the areas in the brain associated with balance, stability, and movement.
We can no longer ignore the unbelievable and groundbreaking impact that vibration training has on improving balance and stability in the human body. What is even more exciting however, is that recent studies have begun to demonstrate that vibration is in fact directly influencing the brain. Up to this point, the focus on the stretch reflex, a reflex that occurs only on the spinal cord level, has prevented us from looking upward . It is time for vibration training and our understanding of the mechanisms behind it to evolve . Considering this century will be dedicated to better understanding the brain, it is a “no-brainer” that an understanding of vibration training will move right alongside it.