Whole body vibration

Whole body vibration (WBV) refers to the transmission to the human body of low frequency environmental vibration in the range of 0.5 to 80 Hz through a broad contact area, such as the feet when standing, the buttocks when sitting, or the reclining body when in contact with the vibrating surface.

Whole body vibration may refer to vibration training, also known as vibration therapy, biomechanical stimulation (BMS), and biomechanical oscillation (BMO), a training method employing low amplitude, low frequency mechanical stimulation to exercise musculoskeletal structures for the improvement of muscle strength, power, and flexibility. Vibration training has been advocated as a therapeutic method in the treatment of osteoporosis, sarcopenia, and metabolic syndrome, and is used in the fitness industry, physical therapy, rehabilitation, professional sports, and beauty and wellness applications.

Whole body vibration may also refer to the vibration exposures found in many occupational settings such as heavy construction, forklift operation, vehicle operation, and farming. Occupational WBV exposure, especially when chronic, is suspected to cause adverse health effects such as fatigue, lower back pain, vision problems, interference with or irritation to the lungs, abdomen, or bladder, and adverse effects to the digestive, genital/urinary, and female reproductive systems. Mandatory standards for regulation and monitoring of worker exposure to WBV exist in Europe; in the U.S., there are reference standards but no specific regulations.

Background
In the 1880s and 1890s, John Harvey Kellogg was utilizing vibrating chairs, platforms and bars at his Battle Creek, Michigan sanitarium. These methods were part of his "wellness" strategies for inpatient and outpatient populations.

The immediate predecessor of modern vibration training is Rhythmic Neuromuscular Stimulation (RNS). In former East Germany Biermann was experimenting with the use of cyclic massage and its effects on trunk flexion back in the sixties (Biermann, 1960 ).

In that same era the Russian scientist Nazarov translated these findings into practical uses for athletes. He observed a substantial increase in flexibility and strength after the application of vibrations in the athletes he studied (Kunnemeyer & Smidtbleicher, 1997 ). The Russians also carried out experiments with "Biomechanical Stimulation" for the benefit of their athletes as well as in their space program. Unlike WBV devices on which the user stands, Biomechanical Stimulation uses vibration stimulation directly on muscles or tendons.

Due to the lack of gravity in space, astronauts and cosmonauts exhibited muscle atrophy (muscle impairment) and bone loss, which forces them to return to earth rather quickly. To prevent muscle and bone loss on long term mission the European Space Agency as well as the DLR are experimenting with various types of vibration training systems as a supplement to other fitness training.

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 (Marin PJ, Rhea MR, 2010 ). Main categories of machine types are: 1. High Energy Lineal, found mostly in commercial vibration training studios and gyms. The vibration direction is lineal/upward eliciting a strong stretch-reflex contraction in muscle fibres targeted by the positions of training program. 2. Premium Speed Pivotal, (teeter-totter movement) used for physiotherapy work at lower speeds and exercise workouts at “premium” speed, up to 30 Hz. Both commercial and home units are available. 3. Medium Energy Lineal, the majority of lineal platforms produced. These are usually made of plastic; some have 3-D vibration which is low quality. They give slower and less consistent results. 4. Low Speed Pivotal units. These can give “therapy” benefits. Other machine types are low Energy/Low amplitude lineal and Low energy/High amplitude lineal with varying uses from osteoporosis prevention, therapy for improved blood circulation and flexibility and limited fitness training.

In order to elicit a stretch reflex in the muscles, the major contributing factor to the training results that can be achieved with vibrating platforms, the up-down movement is the most important. The platform is vibrated upwards to work directly against gravity and therefore is called "hyper-gravity". High Energy Lineal Machines can overload the muscles up to 6 times(6G)in the upward phase; meaning the person on the platform is weight training using their own body mass.

The training frequency (Hz) is another of the important factors involved. The human body is designed to absorb vertical vibrations better due to the effects of gravity; however, many machines vibrate in more than one direction: sideways (x), front and back (y) and up and down (z). The z-axis has the largest amplitude and is the most defining component in generating and inducing muscle contractions.

Concerning the z-movements, two main types of system can be distinguished (Marin PJ et al. 2010, Rittweger 2010, Rauch 2010 ) : Systems with side alternation usually offer a larger amplitude of oscillation and a frequency range of about 5 Hz to 35 Hz. Linear/upright systems offer lower amplitudes but higher frequencies in the range of 20 Hz to 50 Hz. Despite the larger amplitudes of side-alternating systems, the vibration (acceleration) transmitted to the head is significantly smaller than in non side-alternating systems (Abercromby et al. 2007 ). This difference can be a determining factor when choosing a platform for therapy versus training effects.
 * Side alternating (pivotal) 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.

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 (Abercromby et al. 2007, Burkhardt 2006 ).

Due to this subconscious contraction of the muscles, many more muscle fibers are used than in a conscious, voluntary movement (Issurin & Tenenbaum 1999 ). This is also obvious from the heightened EMG activity (Bosco et al. 1999, Delecluse et al. 2003 ).

Immediate and short term
More motor units (and the correlating muscle fibers) are activated under the influence of vibration than in normal, conscious muscle contractions. Due to this, muscles are incited more efficiently (Paradisis & Zacharogiannis 2007; Lamont et al. 2006; Cormie et al. 2006; Bosco et al. 1999, 2000; Rittweger 2001, 2002; Abercromby et al. 2005; Amonette et al. 2005 ). The immediate effect of WBV is therefore that the muscles can be used quickly and efficiently, rendering them capable of producing more force. However, this process will only be effective if the stimulus is not too intense and does not last too long, because otherwise performance will diminish due to fatigue.

Another immediate effect of WBV is an improvement of circulation. The rapid contraction and relaxation of the muscles at 20 to 50 times per second basically works as a pump on the blood vessels and lymphatic vessels, increasing the speed of the blood flow through the body (Kerschan-Schindl et al. 2001; Lohman et al. 2007 ). Subjects often experience this as a tingling, prickling, warm sensation in the skin. Both Stewart (2005 ) and Oliveri (1989 ) describe the appearance of vasodilatation (widening of the blood vessels) as a result of vibration.

Long term
In order to have any effect on the body in the long term it is vital that the body systems experience fatigue or some sort of light stress. As in other kinds of training, when the body is overloaded repeatedly and regularly, the principle of supercompensation applies. This principle is the cause of the body adapting to loading. In other words: performance will increase.

This effect has been proven several times in scientific research for both young and elderly subjects (Roelants et al. 2004, Delecluse et al. 2003, Verschueren et al. 2004, Paradisis et al. 2007 ). The only placebo-controlled study to date (Delecluse et al. 2003 ) concluded "specific Whole Body Vibration protocol of 5 weeks had no surplus value upon the conventional training program to improve speed-strength performance in sprint-trained athletes". Therefore there is no clear indication that the vibrations actually do have added value when performing static exercises.

From research into the structural effects of vibration training it can be deduced that the increased strength resulting from WBV training can definitely be compared to the results that can be attained with conventional methods of training. But there are indications that better results may be achieved with WBV in the area of explosive power (Delecluse et al. 2003 ).

Another important difference between conventional training methods and WBV is that there is only a minimum of loading. No additional weights are necessary, which ensures that there is very little loading to passive structures such as bones, ligaments and joints. That is why WBV is highly suited to people that are difficult to train due to old age, illness, disorders, weight or injury. On the other hand, it is also highly suitable for professional athletes who want to stimulate and strengthen their muscles without overloading joints and the rest of the physical system (Cochrane et al. 2005; Mahieu et al. 2006 ).

Other than its influence on the muscles, WBV can also have a positive effect on bone mineral density. Vibrations cause compression and remodeling of the bone tissue Mechanostat,  activating the osteoblasts (bone building cells), while reducing the activity of the osteoclasts (cells that break bone down). Repeated stimulation of this system, combined with the increased pull on the bones by the muscles, will increase bone mineral density over time. It is also likely that improved circulation and the related bone perfusion due to a better supply of nutrients, which are also more able to penetrate the bone tissue, are contributing factors (Verschueren 2004, Jordan 2005, Olof Johnell & John Eisman, 2004, Rubin et al. 2004 ).

Furthermore the Berlin Bedrest Study (BBR) proved that 10 minutes of vibration training 6 times a week prevented muscle and bone loss in total bedrest over 55 days (Rittweger et al. 2004, Felsenberg et al. 2004, Bleeker et al. 2005, Blottner et al. 2006 ).

In preventing falls and the bone fractures that often result from them, enhancing bone mineral density is not the only important issue. Increased muscle power, postural control and balance are also factors worthy of consideration. Studies involving elderly subjects have shown that all of these issues can be improved using whole body vibration (Roelants et al. 2004, Bautmans et al. 2005, Bogaerts et al. 2007, Kawanabe et al. 2007 ).

Criticism
Although much research has covered these areas (bone mineral density, circulation etc.), research currently only suggests an effect on weight loss when also reducing caloric intake. It is also not clear that the effects of whole body vibration can give similar results as that of regular exercise. In reality, vibration machines are not a replacement for weight loss and healthy living, and those under this impression are at a risk of neglecting their health. A study by Roelants et al. (2004) found that 24 weeks of whole body vibration did “not reduce weight, total body fat or subcutaneous fat in previously untrained females.”

A study on previous research findings completed in July 2012 found that no causality can be shown between whole-body vibration and abnormal spinal imaging findings.

Literature

 * Albasini, Alfio; Krause, Martin; and Rembitzki, Ingo. (2010). Using Whole Body Vibration in Physical Therapy and Sport: Clinical Practice and Treatment Exercises. London: Churchill Livingstone. ISBN 978-0-7020-3173-1.
 * International Organization for Standardization (ISO). (1997). ISO 2631-1:1997. Mechanical shock and vibration: Evaluation of human exposure to whole-body vibration — Part 1: General requirements. Geneva: International Organization for Standardization.
 * Mansfield, Neil J. (2005). Human Response to Vibration. Boca Raton, FL: CRC Press. ISBN 0-415-28239-X.