ISO Standard 2631-1 (1997) recognised the damage that Whole Body Vibration (WBV) can pose to health, and it defines the measurement of the exposure to vibration, and the limits before action is needed to protect health.
More precisely it defines:
- A method for testing the vibration that a person in a seated position (including a wheelchair user) is exposed to
- The maximum amount of time per day that, if regularly exposed to, creates a health risk that should be acted on (Termed “Act.” in the standard)
- The maximum amount of time in any single event before action to reduce risk should be taken (Termed “Exp.” in the standard)
- Use the Larson Davis HVM200 accelerometer, which has been calibrated to measure against ISO 2631-1
- Use a standardised and replicable method
- Create test tracks of tarmac/black top and gravel
- Measure vibration at 6kph, 12kph and 18kph, which approximate average user speeds when using a power attachment.
- To remove the distortion of front castor vibration and to create an even speed all wheels were tested with a TriRide power attachment.
- All wheels were fitted on the same Roma wheelchair with same user weight (90kg) and ride position.
Results at 12 kph on Tarmac:
- aRMS is the “root mean squared” of the total frequencies the user was exposed to. This is a standard mathematical process.
- A(8) Exp is the maximum amount of time, in hours, that a user should be exposed to.
- A (8) Act is the Action Value, in hours. This should be acted on, to protect health, if a user regularly goes over that time.
If we convert the fractions of an hour from the ATV into minutes, we get the average amount of time per day that each wheel can be used before action should be taken to protect health.
- Spinergy Day Wheel: 1 hour 3 mins
- Softwheel: 1 hour 18 mins
- Metal Spoked: 1 hour 19 mins
- Loopwheel Classic: 1 hour 41 mins (+60.9% v’s Spinergy)
- Loopwheel Extreme: 2 hours 10 minutes (+109% v’s Spinergy)