Research Evidence of the Benefits of the Natural-Fit Handrim

The research evidence (detailed below) demonstrates that you pay a price with every push on the skinny, round tube standard handrim. The price is less efficiency, more effort, and more fatigue and pain. In contrast, the same research shows that the ergonomic grip of the Natural-Fit improves performance and efficiency with every push:

  • The Natural-Fit provides a 16% reduction in effort to grip the rim.
  • You can cover the same ground with less work and less fatigue.
  • Multiply the effort saved on every push by 2000-3000 - that's the average number of times wheelchair users push on their handrim in a single day.

Ergonomic Grip Matters. Every Push. Every Day.

Background and Details of the Research

The Natural-Fit is the most extensively researched wheelchair handrim on the market today. Two published papers demonstrate the extent to which the Natural-Fit benefits the end-user by improving the grip on the handrim, making wheelchair propulsion more efficient, and reducing pain in the hands and wrists. One paper was published in 2006 in the journal Assistive Technology (Volume 18, pp. 123-143), and another was published in 2008 in the Journal of Spinal Cord Medicine (Volume 31, pp. 62-69). Research on the Natural-Fit has also been funded by the National Institutes of Health (NIH) through their Small Business Innovation Research (SBIR) program (Grant #R43 HD39962-01). Here are some highlights from the published research:

Two comprehensive questionnaire studies were conducted with users of the Natural-Fit:

  • In a 2004 study, 46 users completed questionnaires.
  • In a 2005 study, 82 users completed questionnaires.
  • Responses to questionnaires in both studies were anonymous.
  • Use of the Natural-Fit in these two studies ranged from 2 weeks to over 2 years, and average duration of use was 6-9 months.

The results of both questionnaires indicated that the Natural-Fit led to important reductions in pain in the hands and wrists. Since using the Natural-Fit:

  • 76%-85% of respondents reported less pain in the hands.
  • 71%-80% of respondents reported less pain in the wrists.
  • Reports of reduced pain were more pronounced as time using the Natural-Fit increased.

The 2005 questionnaire also examined daily function. Since using the Natural-Fit:

  • 67% of respondents reported that daily tasks were "less work".
  • Each of eight activities of daily living were perceived, on average, as less difficult.

NIH-Funded Research: The Effect on Wheelchair Propulsion Biomechanics

  • The National Institutes of Health (NIH) funded research comparing wheelchair propulsion efficiency when using the Natural-Fit versus using a standard handrim.
  • A prototype Natural-Fit Handrim was used during a two-week trial period with before and after measurements of propulsion efficiency.
  • After the two-week trial use period, wheelchair users generated significantly more forward force with a lower hand gripping moment (16% reduction in effort to grip the rim) with the Natural-Fit than with a standard handrim.
    • With the Natural-Fit, hand gripping moments were reduced without any reduction in overall power output toward propelling the wheelchair. This means that less work was required to acheive the same outcome.
    • This the best indication of a healthier propulsion stroke with the Natural-Fit Handrim.

References for Research Summarized Above:

Koontz, A.M., Yang, Y., Boninger, D.S., Kanaly, J., Cooper, R.A., Boninger, M.L., Dieruf, K., Ewer, L. (2006). Investigation of the Performance of an Ergonomic Handrim as a Pain-Relieving Intervention for Manual Wheelchair Users, Assistive Technology, 18, 123-143.

Dieruf, K., Ewer, L., Boninger, D.S. (2008). Factors related to improved symptoms and function with use of the Natural-Fit contoured wheelchair handrims, Journal of Spinal Cord Medicine, 31, 62-69.

The NIH-Funded Research described above is based on data provided by one of the most sophisticated and heavily validated wheelchair propulsion measurement tools (the SmartWheel), and has been conducted by one of the most respected teams of wheelchair propulsion biomechanics researchers, Dr. Michael L. Boninger and Dr. Rory A. Cooper, researchers at the University of Pittsburgh, one of our partner research institutions.

Carpal Tunnel Syndrome & Repetitive Stress Injuries

Research has linked the stress and strain that wheelchair propulsion exerts on the arms to the development of Carpal Tunnel Syndrome (CTS) and wrist pain. For instance, research has shown that damage to the median nerve, a cause of CTS, has been associated with high-force, high-repetition tasks commonly experienced during manual wheelchair propulsion. In one study conducted over a multi-year period, the way an individual propelled their wheelchair predicted the onset of CTS years later.

The way an individual propels their wheelchair has also been linked to the development of repetitive stress injuries (RSI) and shoulder pain. Research has shown that individuals who propel with a greater percentage of radial force (force directed down into the axle of the wheelchair) are at greater risk of progressively worse shoulder injuries over time.

Taken together, the research on CTS and RSI (which we have only briefly described here) suggests that the manner in which people propel their wheelchairs is likely to influence the development over time of pain and injury in both the wrist and shoulder areas. Because the Natural-Fit Handrim reduces the stress and strain on the arms by facilitating more efficient wheelchair propulsion and reducing stress on the carpal tunnel, it may help to delay the onset of CTS and RSI and, if these conditions already exist, it will help to reduce the pain associated with these injuries, as the above research indicates.

Natural-Fit Research References - This is a list of research references relevant to the Natural-Fit (supporting a letter of medical necessity) and relevant to research on RSI, CTS, paraplegia, and wheelchair propulsion.

For any other questions you may have, please call us at 509-416-4317 or e-mail us at

We Don't Make the Wheelchair. We Make the Wheelchair Better.
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