Whole body vibration

Whole body vibration (WBV) is a generic term used when vibrations (mechanical oscillations) 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. Human’s 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 (above 50 Hz) enter though the hands, occupational safety concerns may arise. For example, when working with a jackhammer and the development of 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 review in 2014 came to the conclusion that there is little and inconsistent evidence that acute and/or chronic whole body vibration could improve the performance of competitive and/or elite athletes.

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 extremely prevalent in situations where medically injured patients are transported. The discomfort due to vibration can estimated in various environments.

Workplace exposures 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 operatorsof aircraft, workers on-board sea vessels, drivers of public transportation including trains and buses among others. Farmers with long-term exposure to whole body vibration and mechanical shocks have a higher prevalence of back pain (compared to those not exposed to vibration), and the prevalence increases with vibration dose. Long-term exposure affecting the whole body leads to spinal degeneration (spondylosis) 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.

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 (litter), ground ambulance, and air medical services which all contain multiple forms of shocks and whole-body vibrations.

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 is the deliberate exposure to the body of varying frequencies/amplitudes/forces using certain joint angles for any limited time (approximately 1 minute sets). It is also known as vibration therapy, biomechanical stimulation (BMS), mechanostimulation and biomechanical oscillation (BMO). It employs low amplitude, low frequency mechanical stimulation. It can be pivotal (vibrating from side to side) or lineal (vibrating up and down).

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