Curious about vibration technology? It's the latest technology to hit the industry, with a host of manufacturers offering their own products. Find out about the products' history, relevant research and practical applications for your fitness center.
The fitness industry is always looking for things that are scientifically valid, add excitement to exercise and improve results. Whole Body Vibration (WBV) has been touted as a way to improve everything from strength to hormones. At the FIBO 2006 show, there were 31 WBV equipment manufacturers, and consumers are beginning to see clever ads linking improved health to inexpensive, home gym versions.
Vibration training can be a useful warm-up modality before an exercise session or athletic performance.
This is not a case of too good to be true but, rather, true within the context of WBV machine benefits. They do work - but not for everything, and not for everyone. Their place in the commercial market is dependent on type, use and guided versus unguided application. Until now, their primary use has been in therapy clinics and for training professional athletes. WBV machines offer a variety of exercises, but the question is, which exercises and applications are commercially viable? Users can stand on a WBV machine in a squat position, move dynamically, stretch, balance, and even perform resistance-training exercises or plyometrics. Not many protocols are set in stone; instead, they are determined by the training paradigm of the fitness professional. If there are drawbacks, WBV requires a well-designed program to be effective and, for self-guided use, a good educational program and instructional materials.
The specifics are sketchy, but it appears that the Russians and Dutch originally developed WBV as a tool sometime in the 1970s. The Russian scientist, Nazarov, was reportedly the first to explore vibration, with other studies performed by an Israeli scientist, Issurin. They found that standing on a vibrating plate produced a number of positive benefits, including increases in bone density and leg strength. Some other initial research was performed in Germany on a teeter-totter-type platform. What looked like machines made in a garage became a bona-fide exercise category in the late 1990s, when the first commercial units were manufactured by Galileo (now VibraFlex), followed by PowerPlate in 2000. Contributing to the growth of WBV was the success experienced by Dutch speed skaters, and an accumulating body of evidence that demonstrated a number of health and performance applications. The Russians found this device potentially useful at countering the long periods of weightlessness in space, as it helped to maintain astronauts' bone density. WBV as a possible intervention for osteoporosis helped to fuel the popularity of both low-end home machines and commercial units. Initially, the machines were solid plates, some with handlebars and some without. Now, machines have handlebars, programmable controls, and weight limits up to 1,500 pounds, which allows for plyometric training and Olympic-style weightlifting to be performed on the plates. Rather than being a defined technology with set protocols and applications, WBV can be described as a category in the launch stage, just getting off the ground.
Not so fast
Excessive vibration, especially connected with an occupation, such as operating a jackhammer, has been demonstrated to cause numbness, loss of circulation, joint damage and other harmful effects. However, these applications occur for hours at a time, not a five-minute session. Such organizations as the Occupational Safety and Health Administration and the American National Standards Institute, as well as work-safety experts, have suggested limitations to vibration exposure. In July 2005, Control of Vibration at Work Regulations was issued in the United Kingdom. This document set standards for both hand and WBV exposure, which is directly linked to the magnitude of the vibration, combined with exposure time. Obviously, exposure to excessive vibration in the workplace for up to 40 hours per week is quite different than using WBV as an intermittent fitness or therapy modality.
WBV, and even the few hand-held units on the market, work with four variables that act on the human body. Hertz (Hz) are the cycles per second, which is essentially the vibration speed. Amplitude, or the depth or travel of the vibration, is generally measured in millimeters, and is a factor that determines intensity (most machines have high and low settings). On a fixed platform, users can change the distance the vibration travels. On a tilting platform, users change the amplitude by using a wider stance. On a sound-driven machine, users turn up the volume. Magnitude, or the acceleration power of the movement, is a measure of the mechanism and its movement through space and time. Duration is the amount of time spent on the machine. How users adjust these variables determines their results, and the type of machine also determines how they adjust the variables. How vibration affects the body involves a number of reactions and systems. As the plate vibrates, the body goes through relatively quick oscillations, when states of more or less gravity are alternately applied. Vibration stimulates innate muscle spindle activation. The rapid continual firing of this mechanism, due to vibration, is known as the Tonic Vibrational Reflex (TVR). The effect on the muscular system - especially when flexed, such as in a half squat - is to fire the stretch reflex (SR) through the muscle spindles to add muscular force. In addition, the golgi tendon organs (GTO) are activated by relatively strong contractions, lessening the force on the muscle as a protective mechanism. Theoretically, the muscles are fired, relaxed somewhat and fired again in this scenario, in response to WBV. However, just because something vibrates doesn't mean it invokes these physiological mechanisms. There is some evidence that at 8 to 10 Hz, the SR is not activated the same way it is as at 25 Hz. Positioning and movement obviously would elicit a smaller or greater response, in addition to Hz and amplitude variation.
Further research is needed to discover the placement of vibration training within an overall conditioning program.
In terms of hormonal system changes, there have been reports of similar increases in testosterone and growth hormone to resistance training, with some speculation that the physiological responses to mechanical vibration are tied to these effects. However, as there appears to be less stress on the body with WBV compared to weight training, Cortisol (a measure of stress response) has been lower in response to WBV. WBV activates the joint receptors to supply increased information about body position and state of posture. Mechanoreceptors respond to both passive and active movement, as well as the range of movement speeds.
One of the issues with WBV research to date is that the type of vibration applied, combined with the specific exercise, time and frequency, all determine results. Because there are now very different forms of vibration, it is difficult, without comparative studies, to apply research from one type of machine to another. A large portion of the initial research was performed on tilting platforms, and then later performed on fixed platforms. When viewing the available research, it is important to note whether the study looked at changes immediately after a WBV session, or over an extended period of time. There is significant data to strongly indicate that a number of variables improve right after a WBV session, such as strength, explosive abilities, balance, shuttle run speed and flexibility. This points to a conclusion held by many practitioners that WBV can be a useful warm-up modality before an exercise session or athletic performance. Long-term studies, such as those performed by Torvinen, et al., where body balance in non-athletic young adults improved, demonstrates that, over longer periods of time, WBV can improve some physiological measures. Increased bone density, measured by Bone Mineral Density tests, is one of the largest research areas on the positive effects of WBV. Verschueren, et al., studied the effect WBV had over six months on bone density in the hip and postural control, and found significant benefits. Rubin, et al., extended the time of WBV treatment to one year, and found a similar increase in bone density in post-menopausal women. A few studies have found little or no change in young adults, while there have been measurable and positive changes with children and older adults. Some of this may have to do with state of training and previous loads, and just where WBV stimulus fits according to those variables. In other words, with young adults who are active, WBV may not have been significant compared to loads experienced during normal activities. For the older and younger groups, however, WBV was significant. Strength gains have been researched by Bosco, et al., Roelants, et al., and others, looking at leg extensor strength and explosive capabilities. In these studies, WBV showed positive responses in such measures as vertical jumping ability, theorized to be enhanced through increased neurological activation, as well as some muscular development. One of the reasons explosive or power applications show improvement immediately after WBV may be linked to increased neurological activation. Some studies, such as the one done by Abercromby, et al., comparing tilting or teeter-totter to vertical platforms (especially with regard to leg strength), demonstrated that tilting platforms had higher leg activation results as knee angles get more extreme. While it can be argued that all vibration will - if applied at the correct settings and duration - result in strength gains, testers noted that the same Hz level and amplitude did not feel the same on all the test machines. This is an important observation; vibration applications may be mildly specific to the vibration type and application. With regard to strength, overall strength improvement is linked with frequencies of 20 to 27 Hz, yet that doesn't mean higher frequencies/amplitudes or lower amplitudes, if applied correctly, wouldn't lead to significant strength gains. With respect to upper-body exercise devices, such as the Mini by VibraFlex, this area is not well-researched, but it can be conjectured that, if applied within a sound model, results would be positive. Because platforms have recently been developed that allow resistance training and plyometric movements (specifically, The Wave and Pneumex), it would be reasonable to expect that future research will address combining WBV with more aggressive movements. It may be that the studies to date that demonstrated no or little improvement in explosive capabilities simply did not place vibration within the optimal phase of training with the optimal load/dose for improvement. Further research is still needed to discover the exact placement of WBV within an overall conditioning program, and how it can be "periodized" within a fitness or sports training model that is applicable to various populations and levels of fitness. Flexibility showed significant increases, especially immediately after a bout of WBV, or an acute treatment. Other areas have documented improvement from WBV, including hormonal gains, balance, posture, minor cardiovascular improvements and pain relief.
Types of vibration machines
When first introduced, there were two initial designs. The tilting, or teeter-totter, platforms (VibraFlex and MaxuVibe are examples) were developed with the cross-over pattern of the body in mind (for example, the right hand moves with left leg in walking). Plus, the purported use of leg and hip independence from side to side was taken into consideration. The original fixed plate has vibrations occurring in a vertical plane. Recently, a number of different approaches have been used to modify the vibration output and, theoretically, increase the training effect. Some fixed platforms now offer a combination of vertical, side-to-side and front-to-back vibration (such as PowerPlate). Some machines sense load and adjust structurally to keep Hz cycles/amplitudes constant (Pneumex uses staggered supports at 45-degree angles for this purpose). Air adjustment systems have been developed to compensate for various user weights to keep Hz and amplitude levels constant through increased or decreased pneumatic pressure under the platform (The Wave and PowerPlate). Additionally, one manufacturer uses sound waves under the platform to create minute Hz changes that also start at small Hz levels (Turbosonic). VersaClimber is the first company to apply vibration to exercise machines, and currently has four machines that offer vibration. At the time this article was written, there were reports of new units using two or three motors to apply vibration in various patterns. (See What Machines are Available for a list of companies.)
The scientific evidence makes a case that WBV is a useful and effective modality in rehabilitation, general fitness and sports performance. With the addition of upper-body devices, such as the VibraFlex Mini and the ExerVibe hand-held, you can expect more application to upper-body resistance training. So what would make WBV effective in your facility? First, it is important to educate your staff on WBV and how to use it within a fitness program. According to two industry experts, Mike Boyle and J.C. Santana, with education and such direction as posters/wall charts, members can safely and effectively use WBV on their own. Also, personal trainers are an important part of the usefulness of WBV in fitness centers. Clients will not only be better educated on the uses of WBV when working with trainers, but other members who see the product in use are more likely to follow suit. And, independent training organizations, like VibroKinetix (www.bettervibrations.com), are emerging to help fitness professionals better use WBV as a training tool. WBV can be effective, with the right knowledge and for the right training goals. Before buying a machine just because it is the latest trend, do your homework to find out if WBV is a right fit for your fitness center.