There’s an International Standards Organization chart (from ISO-2631) dealing with vibration safety in chronic exposure, but it does not specify displacement:
Is it simply a bureaucratic error, that this chart does not explicitly or implicitly refer to a displacement? Read below to understand why it is true that without displacement, this chart is entirely useless.
Safety is about a machine’s impact (or “impulse“) on you.
With very little movement of its stainless steel platform, The Whole Body Vibrator has much less “impact” on your body than machines that are often compared to WBV, where safety is concerned:
- riding on an old, bumpy train every day, while sitting in a seat without padding
- operating a jack hammer
- driving a tractor without a comfortable, isolated, padded seat… etc…
Imagine standing in an elevator. You feel the acceleration when it starts. That’s work being done on you; but the acceleration is very low, so you don’t feel much “impact”.
Work = Force x Distance
An elevator accelerates slowly (the force on you is low), but you move very far, so the elevator does a lot of work on your body. But the total work done to lift you up a floor or more, is elapsed over a long period of time. Thus the “impact” is very low:
Work done, in a short period of time, is a high impact.
The same work done, in a long period of time, is a low impact.
The Whole Body Vibrator, puts more force on you than an elevator, but its stainless steel platform moves only a very small distance. Thus a Linear WBV machine does relatively little work on your body.
However, this little bit of work is done in a very short period of time — making a “high impact” possible. But the fact remains that the distance is very small, and the force is carefully designed so that the total impact on you is not comparable to a jack hammer or sitting on a steam-punk locomotive without a padded seat.
DISPLACEMENT IS VERY IMPORTANT
Imagine standing on a WBV machine that was somehow built to move up 1 foot and down 1 foot, at 30Hz (30 times per second , the same as in the Whole Body Vibrator). You wouldn’t need to know what “acceleration” is for this 1-foot monster machine. Just seeing it in motion you’d understand that it’s very dangerous. It moves very fast, to travel back and forth 30 times per second.
The Whole Body Vibrator’s platform doesn’t have to move as fast, to travel a tiny distance 30 times per second. It moves less than 0.05″ inches up and 0.05″ down. With that very low displacement it would take a much higher acceleration to have a harmful affect. This is described by the graphic of “G’s” on the Performance Data page.
THE WHOLE BODY VIBRATOR IS NOT RECOMMENDED FOR PEOPLE UNDER 100 POUNDS
With all that said, The Whole Body Vibrator could be dangerous for a person weighing less than 100 pounds:
- If you weigh under 100 pounds, the acceleration can exceed the suggested 7 G’s “comfort limit”.
- You are responsible for discerning whether an impact is detrimentally “jarring” on your body, as described in the “G’s” graphic on the Performance Data page.
- “Ask your doctor” is a disclaimer here. But that may not be worth your time. Most doctor’s know very little about health.
A WELL DESIGNED WBV MACHINE ISN’T COMPARABLE TO DANGEROUS POWER TOOLS
Holding a jack hammer, riding on a tractor, bumpy train, etc. Vibration from these machines means a significant distance, and they move very fast. That combination has a “jarring” affect on the body, and recurring exposure to that sort of vibration is dangerous.