The first self-propelled push-rim wheelchair was patented in 1881 by James Heath. While wheelchair design has evolved considerably since then, the basic concept of push-rim propulsion has remained largely unchanged, despite the fact that our understanding of the human body has grown leaps and bounds beyond what it was at that time.
If we look at modern medicine in general, we see huge leaps forward.
For historical context, around the same time push-rims were invented, Bayer was promoting heroin as a new, highly effective children’s cough suppressant.
Thankfully, we’ve learned and changed a lot since then!
Today, we know that the motion required to propel a push-rim wheelchair is an extremely inefficient use of energy. Typically, about 90% of the energy a wheelchair rider uses to propel their push-rim chair is wasted.
This is largely because propelling a push-rim requires the use of many small muscles primarily around the shoulder, which is why such a high percentage of manual wheelchair riders will develop shoulder pain in their lifetime, sometimes leading to overuse injuries like muscle strain, rotator cuff tears, and impingement.
Any repetitive movement – like transfers and reaching overhead to grab things – can add to the likelihood of overuse injuries, which is why it doesn’t make a lot of sense to use these muscles even more for propulsion when they are already required for other day-to-day tasks. It may sound grim, but don’t panic.
Recently, nearly 150 years after the advent of the push-rim, a new type of propulsion system is gaining popularity: the lever drive.
Like the name implies, levers give you leverage, amplifying your push force with each stroke. A lever drive – like the one used to propel the GRIT Freedom Chair – doesn’t just reduce the likelihood of shoulder strain: it actively helps prevent it.
When riders push on the lever, they are using the triceps, pectorals, and deltoids. These are large muscles intended for bearing heavy weight. Strengthening them assists in the restoration of muscle balance and helps to prevent the shoulder strain that often leads to injury.
Using larger muscles for propulsion also means you’re using your energy more efficiently, so you can go further and faster while expending less effort then you’d need to propel a push-rim. Additionally, with a lever drive many riders who were previously limited to a power chair now have the opportunity to self-propel, build muscles, and get the benefits of cardio.
This causes a positive snowball effect: the more you self-propel the more you build muscle strength and endurance, which allows you to self-propel further and build even more muscle strength and endurance.
The GRIT Freedom Chair packs its lever drive onto an all-terrain frame, taking this idea beyond the pavement. Thanks to a three-wheel design that can tackle any terrain and the use of mountain bike tires, you can enjoy its benefits on the trail, at the beach, or in your backyard.
There are also several types of lever drives, like the Wijit, that can be fitted to your standard manual chair. It’s been over a century since the invention of the push-rim –and it was long overdue for a major upgrade.
The GRIT Freedom Chair is the most versatile chair on the market, designed from the ground up to handle any terrain. From trails to grass to snow, the Freedom Chair is built for you to push yourself. Born out of research at MIT, the Freedom Chair’s patented easy-push levers reduce shoulder strain and put you in control of your mobility. Moving parts are composed of standard bicycle parts, so it’s easy to customize or repair at your local bike shop. Ready to hit the trails? Learn more about the GRIT Freedom Chair at www.gogrit.us.
