Vibratory stimulus and its effects on performance physiology
December 2005 – NetworkMag
Author: Juan Carlos Santana
The popularity of functional training has forced many fitness professionals to take a second look at some of the traditional training concepts. Discussions regarding functional training have often become heated at conferences and seminars. One of the topics generating a significant amount of debate is the efficacy of training in unstable training environments. More specifically, the topic of vibration training, a form of unstable training, has received much attention in recent months.
Confusion surrounding unstable training environments revolves around the assumption that functional training exclusively uses training in unstable environments to enhance strength and performance. It is important to know that: functional training involves much more than unstable training. Functional training encompasses a multi-disciplinary approach to training. It involves the use of a wide variety of modalities and specific movement patterns for the purpose of enhancing performance and rehabilitation, the use of unstable training just happens to be one of those modalities.
Functional training uses unstable training environments to improve performance through enhanced stability and balance. One of the reasons this type of training is debated may be because many exercises performed in unstable training environments have been lapelled ‘functional’ just because they are hard to perform and look different (e.g., barbell squats on a stability ball). This exaggerated methodology and misrepresentation of functional training may be what has fuelled arguments against the use of unstable training environments. Perhaps some clarity may be useful in bringing strength and conditioning professionals to a common ground of discussion.
Stability and balance training in unstable training environments is no more effective than any other performance enhancement method; specificity still governs the training adaptation. The use and effectiveness of this training approach has been proven in the field, in the gym and in the lab. However, this does not mean it is the magic potion. For example, framing in unstable environments would certainly not be my first choice to develop hypertrophy or explosiveness. Having said that, I would certainly incorporate a measured dose of stability training (i.e., using an unstable training environment) within any hypertrophy or power program to help direct and control the size and power my program will provide.
Scientific data shows the efficacy of unstable training environments. For example, a recent study, published in Physical Therapy by Vera Garcia, Grenier and McGill showed increased core muscle recruitment during an abdominal curl when performed in an unstable environment, compared to a stable surface. Research (by Eils and Rosenbaum and published in Medical Science Sports Exercise) has also demonstrated the efficacy of using unstable training environments when rehabilitating the ankle complex with a multi- station proprioceptive exercise program. Training under vibratory stimulus, which can be seen as a form of an unstable training environment, has also been shown to enhance performance parameters, such as a vertical jump. Vibratory stimulus deserves a more detailed review due to its current popularity.
Vibration training is one of the new methods of unstable training, Multiple studies have now been conducted on the effects of vibration training on different parameters of performance and physiology. The curiosity with vibration dates back to 1965, when the Tonic Vibration Reflex (TVR) was first defined. This phenomenon described a reflex muscle contraction that ensued after mechanical vibrations were felt by muscles. It is believed that vibration training may enhance activation of the muscle spindles, leading to an enhancement of the ‘reflex loop’. Furthermore, it is believed that the higher EMG readings illustrated during vibration training, when compared to voluntary contractions training, could be related to an increase in motor unit synchronisation. The reflex muscle activity noted in vibration framing is thought to be a response of the central nervous system to strong perturbations (i.e., a disturbance of motion, course, arrangement or state of equilibrium).
Most of the vibration frequencies studied have been between 26Hz and 44Hz. Various implements have been researched, from vibrating dumbbells to total body platforms. The studies have shown some positive adaptations to vibration training, although the mechanism of action and the optimal protocol still evade scientists. There are many questions that must be answered before going out and spending $US7000 to $US10000 for a vibration platform. Below are some practical questions we need to consider before we jump onto the very expensive, vibration bandwagon.
1. Is all vibration training created equal? What frequency is optimal? Is the optimal dose of vibration different across muscle groups or body positions?
2. If high vibration frequencies are superior to lower vibration frequencies, is the difference worth an extra $US7000 to $US10000?
3. Can any unstable training, such as a push-up on a stability ball or single leg work with the Bodyblade, provide enough perturbation as to elicit a vibration reflex, or something similar, to provide vibration stimulus?
4. Can the improvements noted in vibration studies be obtained with a combination of other functional modalities?
These questions are just the beginning when it comes to the factors that must be considered before jumping into a purchase of a vibrating platform.
Personally, I find all vibration research interesting and worth continuing. However, I suspect that much the same can be done with stability balls, balance equipment and the proper use of the Bodyblade. I have seen people start to shake when put on the appropriate balance equipment. Anyone that has seen a beginner do a ‘hands on ball’ push up on a stability ball knows what I’m talking about. The same vibratory stimulus can be provided to experts in control of the stability ball by lightly tapping the ball in all directions while a push-up is performed on it. I have also found the Bodyblade provides excellent vibratory stimulus. Although the Bodyblade vibrates at 4.5Hz, it does provide excellent active and dynamic vibration, which may provide a similar effect as higher vibration frequencies not dynamically created by muscles. This issue should be looked at in a controlled research study that would compare high passive frequency (e.g. 40Hz) to low active frequency vibration (e.g. 4.5Hz); however, this type of research has yet to be studied.
We must remember that all training modalities are tools. Perturbation training, as a form of training on unstable training environments, is just one of the many tools in today’s fitness and performance environment. The neural control developed from this approach to balance and stability training has been well documented in our practice, as well as throughout many facilities housing qualified trainers and coaches. Although the exact mechanisms of action and optimal protocols have yet to be determined, vibratory training is one of the many promising modalities that make functional training as exciting as it is.