Whole body vibration
Whole body vibration is a generic term used when vibrations of any frequency are transferred to the human body. Humans are exposed to vibration through a contact surface that is in a mechanical vibrating state. Humans are generally exposed to many different forms of vibration in their daily lives. This could be a driver's seat, a moving train platform, through a power tool, a training platform, or one of countless other devices. It is a potential form of occupational hazard, particularly after years of exposure.
When high frequency vibrations enter through the hands, occupational safety concerns may arise. For example, working with a jackhammer has been known to develop vibration white finger. Exposures and limits have been estimated in the ISO 5349-1 for hand-transmitted vibration.
Whole body vibration training as a form of physical exercise can offer some fitness and health benefits, but it is not clear if it is as beneficial as regular physical exercise. A 2018 meta-analysis has shown that whole body vibration can improve bone mineral density in the lumbar spine of postmenopausal women as well as the femoral neck of postmenopausal women younger than 65.
As a hazard
Humans are sensitive to mechanical oscillations ranging in frequency from well below 1 Hz up to 100 Hz. Lower frequencies of vibration lead to human motion sickness while higher frequencies can lead to general annoyance and discomfort. The minimization of discomfort due to vehicle vibration is important in the automotive industry where ride quality is important. Discomfort and even pain may be extremely prevalent in situations where medically injured patients are transported. The discomfort due to vibration can be estimated in various environments.Workplace exposure
to whole-body vibrations for long durations can lead to musculoskeletal problems of many kinds. Problems of the neck and lower back in particular can be common for operators of heavy equipment including construction, forestry, agriculture, and trucking. Other occupations where whole-body vibrations may be present include aircraft operators, sea vessel workers, drivers of public transportation like trains and buses.Farmers with long-term exposure to whole body vibration and mechanical shocks have a higher prevalence of back pain, and the prevalence increases with vibration dose. Long-term exposure affecting the whole body leads to spinal degeneration and increased risk of low back pain.
Factors that affect the occupational exposure to whole-body vibration include the frequency of vibrations, the magnitude of vibrations, the daily exposure to vibrations, the standing or seating posture of the operator, the direction of the vibration, and how tightly coupled the human is to the source of the vibration. Exposure limits and estimates have been characterized in the ISO 2631-1 for whole-body vibration. Measurements of vibration exposure are usually taken at the human/vibration interface.
Patient transport
Injured patients can be exposed to shocks and vibrations during transport which can worsen patient conditions due to involuntary motions of the body. Many forms of immobilization devices are used to limit this motion with varying degrees of success. Common modes of patient transport include hand carried stretcher, ground ambulance, and air medical services which all contain multiple forms of shocks and whole-body vibrations.Measurement
Measurements are taken with accelerometers to estimate the amount of vibration exposure to the human body. These measurements are taken at the human body or at the vibration source or surface. Measurements of different directions are taken to relate the motion direction with the response of the human body. Specifically, transfer functions can be used to determine the human response to the vibration. Measurement techniques for estimating exposures to whole body vibrations and hand-arm vibration have been developed in International Standards.Vibration training
Vibration training is the deliberate exposure to the body of varying frequencies/amplitudes/forces using certain joint angles for any limited time. It is also known as vibration therapy,vibrotherapy, biomechanical stimulation, mechanostimulation and biomechanical oscillation. It employs low amplitude, low frequency mechanical stimulation. It can be pivotal/oscillating or lineal.History
The immediate predecessor of modern vibration training is Rhythmic Neuromuscular Stimulation. In former East Germany Biermann was experimenting with the use of cyclic massage and its effects on trunk flexion back in the sixties.The technique has been tested on turkeys in the hope of finding a benefit that could be used for astronauts. Engineering issues came into play when they tried to upgrade the test machine to support the weight of a human being. Once the vibration intensity grew strong enough to lift over 40 kg, fractures appeared in the steel. The first bed-rest study using a vibration training device for humans was done by the European Space Agency in 2003 in Berlin. The same technology was then used in several parabolic flight campaigns of the DLR starting in 2006 where the feasibility of use of a lightweight vibration training device under microgravity conditions was demonstrated and ein 2009 and 2010 where basic research on influence of microgravity on vibration training effects was investigated.
Since 1961, NASA has been testing adding light vibrations to exercise equipment and systems to minimize vibration transmission of existing exercise devices to the space station, like the Treadmill Vibration Isolation System and the Cycle Ergometer Vibration Isolation System. Any company referencing NASA directly in its marketing campaigns is misleading and has no relevance to the discipline of vibration training.
The first Galileo machine patent was filed in 1996 in the same year the first Galileo device was commercially available. In 1996, the first Galileo vibrating dumbbell patent was filed.
Training effects
While it is not yet clear if whole body vibration produces the same health benefits as regular physical exercise, it has been proven to provide significant health benefits, including decreased resting heart rate and blood pressure and improved cardiac function.While it has been shown that whole body vibration at high frequencies can cause low back pain, studies have illustrated that at low frequencies, it can be effective in reducing back pain. A 2019 randomized control trial indicated that low frequency vibration can help people with non specific low back pain by reducing symptoms and improving joint proprioception.
A 2018 meta-analysis showed that whole body vibration can improve bone mineral density in the lumbar spine and femoral neck of postmenopausal women younger than 65. A 2019 publication evaluated the benefits of whole body vibration in pediatric oncology patients. Whole body vibration applied at frequencies ranging from 12 to 30 Hz was shown to improve balance and muscle strength of several muscle groups in the legs. This review concluded that whole body vibration is a therapeutic modality that can offset functional impairments in children with cancer. Whole body vibration should be used in conjunction with an exercise therapy program to promote an active lifestyle.
A review in 2014 concluded that there is little and inconsistent evidence that acute or chronic whole body vibration could improve the performance of competitive or elite athletes.
Cochrane reviews have concluded that there is insufficient evidence of effect of whole body vibration training on functional performance of people with neurodegenerative disease, or in disease-related problems in people with fibromyalgia.
Vibrating platform types
Vibrating platforms fall into different, distinct categories. The type of platform used is a moderator of the effect and result of the training or therapy performed. Main categories of machine types are:- High Energy Linear, found mostly in commercial vibration training studios and gyms. The vibration direction is lineal/upward
- Premium Speed Pivotal, used for physiotherapy work at lower speeds and exercise workouts at “premium” speed, up to 30 Hz. Both commercial and home units are available.
- Medium Energy Lineal, the majority of lineal platforms produced. These are usually made of plastic; some have 3-D vibration which is low quality.
- Low Speed Pivotal units.
Concerning the z-movements, two main types of system can be distinguished :
- Side alternating systems, operating like a see-saw and hence mimicking the human gait where one foot is always moving upwards and the other one downwards, and
- Linear systems where the whole platform is mainly doing the same motion, respectively: both feet are moved upwards or downwards at the same time.
Despite the larger amplitudes of side-alternating systems, the vibration transmitted to the head is significantly smaller than in non side-alternating systems while at the same time muscle activation even at identical vibration parameters are increased in pivotal systems. However, standing with both heels on one side of a side-alternating machine facing side-ways results in significant acceleration transmitted to the head and center of gravity of the upper body. At least one such WBV owner's manual suggest this variation calling it "Stand-a-side Pose". At the outer edge of the plate the amplitude is typically about 10 mm, which is more than the 3 mm maximum of a linear vibrator and not practical. The amplitude and impact can be reduced by centering, e.g., a gardener's knee pad, ~ 16"x 8" x 3/4", on the plate and standing with the heels toward the outer edge of the pad. While this is useful it does not replace a machine whose entire plate moves up and down in a linear fashion allowing for a variety of positions and activities.
Mechanical stimulation generates acceleration forces acting on the body. These forces cause the muscles to lengthen, and this signal is received by the muscle spindle, a small organ in the muscle. This spindle transmits the signal through the central nervous system to the muscles involved.
Power Plate is a brand of vibrating platform consisting of a vibrating base, which may vibrate up and down approximately 25 to 50 times per second. The machine is large enough to accommodate a person in deep squat. Traditional exercises such as squats and push-ups can be done on the vibrating base.
Galileo is a brand of vibration training platforms used as exercise equipment as well as for therapeutic use. It consists of a vibration platform which vibrates sinusoidal side alternating like a see-saw. Depending on the device size it oscillates with an amplitude of up to 6 mm and a frequency of 5 Hz to 40 Hz. Galileo is manufactured in Germany by the German company Novotec Medical GmbH. Since 2004 Galileo is also available as a medical device.
The base plate of Galileo vibration training devices is moving like a see-saw. This side alternating motion is supposed to mimic human gait in order to utilize nearly physiological motion patterns close to the side alternating human gait. The side alternation causes the hip to tilt which requires the contra lateral muscles of the back to be activated – while one leg is lifted the other drops. Compared to vertically vibrating devices the side alternating motion results in very low acceleration acting on the centre of gravity of the upper body and the head. But see the Stand-a-side Pose described above which does result in significant acceleration.