Whole Body Vibration concerns the exposure of the human body to environmental vibration. Adverse health effects from exposure include spinal injuries, abdominal and digestive problems, and cardiovascular disorders. The following presents a basic understanding of whole body vibration, its sources, and how it may be a cause of previously unexplainable injuries and illnesses.


Vibration applied to the human body can cause motion in part or all of the human body. If the vibration moves the entire body, the classification of exposure is generally called wholebody vibration. In special cases involving very low frequency vibration, we refer to the human response as motion sickness. Many times the vibration is isolated in one specific part of the body. With the prevalent use of vibrating handheld tools in the workplace, a frequently occurring occupational illness is hand-arm vibration syndrome or HAVS (Janicak, 35). Depending on vibration's extent of exposure to the body or its parts and its frequency and magnitude, adverse health effects may be expected.

Vibration Basics

Vibration is a wave motion, oscillating about a fixed point. It is a mechanical wave that can cause a transfer of energy from one object to another. A simple type of wave known as the sine wave is characterized by frequency and amplitude, with a measurement of acceleration generally given in meters per second squared (m-s-2). In older literature, acceleration is occasionally reported in "g's", representing the 9.8 m-s-2 acceleration of gravity. In the context of ocean waves, frequency is the distance between the waves, the amplitude is the height of the waves, and the "fixed point" is half way between the trough and crest of the wave. Frequency is expressed in hertz, (Hz), the number of cycles per second such as seen in our household electrical power (110 volts, 60 Hz). However, it would be extremely rare to find a human exposure in a non-laboratory environment where vibration exposure would occur with only a single sine wave. Environmental exposure will almost always involve many simultaneous dissimilar waves from different directions that would be graphed as a relatively "squiggly" line. The total impact of this integrated vibration is of concern in ascertaining the potential for human illness.

The magnitude of vibration is the acceleration. As previously mentioned, vibration isoscillation about a fixed point, with negative and positive values assigned to respective directions of travel above and below this fixed point. Without external complications, the summation of both negative and positive values will cancel out to zero over time. For this reason, vibration is measured in terms of root-mean-square (r.m.s.), still using units of m-s-2. The r.m.s. squares the individual values of the vibration wave, takes the mean, and reduces the means by the square root to eliminate the positive-negative canceling effect by utilizing the squares. The r.m.s. is analogous to the statistical standard deviation function (Mansfield 112).

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