Pittsburgh University Study on In-wheel Suspension

Gemma Pearce avatar

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A new study compares three different wheels for reducing shocks and vibration

The first paper by the University of Pittsburgh on its independent study into the Effects of In-Wheel Suspension on Whole-Body Vibration and Comfort in Manual Wheelchair Users was published in the scientific journal Vibration on 30 April 2024.

The paper compares Loopwheels, Spinergy CLX Wheels and basic spoked wheels. It concludes that the in-wheel suspension in Loopwheels helps reduce harmful levels of shock and vibration.

Why do we care about shock and vibration?

For a long time it’s been shown that frequent and prolonged exposure to high levels of whole body vibration can cause neck and back pain and discomfort for many people who use a wheelchair.

What is whole body vibration?

Whole Body Vibration is typically characterised by both

  • low impact, long-term vibrations  – such as driving over a gravel road; and
  • high impact, short-term shocks  – such hitting a pothole on a smooth road.

Given the risk of health consequences, the International Standards Organisation (ISO) has published several guidelines on levels of vibration exposure and their relationship to health outcomes. Regulations protect workers from over-exposure to whole body vibration in jobs which involve exposure to it, like driving or using machinary.

What did the Pittsburgh study find?

24 manual wheelchair users with Spinal Cord Injury were propelled over nine different surfaces using a standard spoked wheel, a Spinergy CLX, and Loopwheels. Accelerometry data was collected at the footrest, seat, and backrest.

The study found that:

  • Loopwheels are effective at reducing both vibration and shock, significantly reducing the amount of Whole Body Vibration exposure at the backrest and at the footrest
  • Spoked wheels and CLX were not effective at reducing vibration or shock
  • Further study involving long-term testing is required to determine effects on health: Pittsburgh is yet to report on later parts of their study.

Specific findings:

  • Loopwheels lowered vibrations by 10% at the backrest compared to the standard and CLX wheels and by 7% at the footrest compared to the CLX 
  • Loopwheels also reduced shocks by 7% at the backrest compared to the standard wheel and CLX. 
  • Assuming a Manual Wheelchair User occupies their wheelchair for an average of 13 hours a day, a 7-10% reduction in backrest and footrest vibration would reduce the amount of exposure to harmful Whole Body Vibration by around an hour, and potentially increase the amount of time a manual wheelchair user can safely push before it becomes it becomes hazardous to health.

These findings add to the body of knowledge about the benefits of Loopwheels.

This paper reports just on the first phase of the study and tested slow-speed, manual use over 9 different surfaces. Our own work previously has measured how much Loopwheels reduce vibrations at the seat and at faster speeds, using a power attachment that lifts the wheelchair casters off the ground. We found higher levels of reduction in our testing than in this study.

Later this year, we expect the University to publish its findings from the participants using Loopwheels over an extended period.