Co.Design

A Prosthetic Limb That Lets Amputees Ride Bikes

A concept by Art Center student Seth Astle wins the U.S. portion of the James Dyson Award.

A prosthetic limb and bike pedal that allows amputee cyclists to experience a full range of motion has been named as the U.S. winner of the James Dyson Award. Interestingly, for the second year in a row, the winning design is bike-related—last year’s finalist was the Copenhagen Wheel.

Cadence is a concept by Art Center College of Design student Seth Astle, who wanted to focus on helping below-the-knee amputees. Since about 47% of amputees are below-the-knee amputees, he knew his solution would be able to help the largest potential audience possible. As he began his research, he learned that although many below-the-knee amputees are able to use custom limbs designed for particular sports, there were many shortcomings when it came to prosthetics for cycling.

Most protheses are extremely rigid around the ankle and foot, which is great for walking or when you want to stand up straight, but difficult when trying to bike. Biking requires a fluidity of movement, that push and pull of muscle strength, which helps you gain momentum while pedaling. To mimick that muscle power, Cadence uses an elastomeric band which can collect energy while riding. As the foot rotates around the pedal, the stored kinetic energy helps bring the foot and leg back up to the top. (See more visualizations of Astle’s process here.)

The Cadence concept also allows the rider to clip into the pedal, allowing for a more efficient ride. A split toe in the prothesis helps them see where to connect the foot to the clip. And the locking mechanism is made just for amputees, with a clip that’s freed with a backwards motion rather than a pivot of the leg, which is dangerous for amputees. But perhaps most attractive to cyclists is that the prosthetic’s form looks more like the high-tech equipment that they’re using. The sleek shapes and bright colors are more akin to a shiny racing bike or an aerodynamic helmet.

Astle has already won a Gold IDEA award for his concept, which will also be featured in a display at the London 2012 Olympics. You can see the nine other U.S. finalists at the James Dyson Award site. The global winner will be announced on November 8, 2011.

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4 Comments

  • sotto1a

    The narrator keeps saying "paraplegics"  Amputees are not the same as paraplegics who ride handcycles.  

  • Jared

    It is interesting that product designers are getting into the prosthetic field at a relatively rapid rate.  I love that people are designing for this segment which has traditionally been ignored or hidden by the person with the amputation.  I am a Product Desiger and Developer as well as a Prosthetist so I have a keen interest in these specific products.  That being said although they look amazing they are almost never functional.  This particular design does not demonstrate how it attaches or holds onto the limb which is one of the key attributes required to funtion in the prosthesis.  Lack of suspension may prevent the cyclist from utilizing the limb altogether or at least result in significant skin breakdown.  Secondly, most cyclists in this category prefer a rigid ankle mechanism or they avoid the use of a foot altogether in order to maximize the transfer of energy through the pedal, and better contol the arc of motion.  I would love to see some of these incredible designs worked through with a Prosthetist in order to bring the level of function to that of the design.  

  • Renato Castilho

    I'm sorry... while the design of this foot is absolutely stunning and the research very entertaining, I can't help but notice "Cadence" wouldn't work very well. Through this exercise, the designer seems to have learned a little about pedaling and walking-prosthetics, but he forgot to think outside the box. :)

    He failed to realize that energy-storing feet are great for walking, going up stairs and running (particularly the Cheetah), but offer little advantage when pedaling. Mostly because of the lever created by the foot, which reflects stress onto the wrong areas of the residual limb —it is as if the amputee were constantly tiptoeing, which is inefficient and uncomfortable. This is not just the culprit of the "dead spot" amputees complain about but also make it very difficult to stand onto the pedals during "all out" efforts. Learning to rake, to achieve a smooth circular motion, with a clipped prosthetic is hard but not impossible.Moreover, the idea of using an elastic band instead of carbon's incredible attributes seems very backwards to me. There's also no explanation on how Cadence would actually stick to the limb, specially under hard exercise. It might look clean, but it doesn't seem to have enough area of contact for proper adherence through suction.The amazing thing about prosthetics is that one can design for efficiency, free of preconceptions and somehow detached from human evolution. The "Cheetah" leg (incorrectly added to his competitive analysis) was conceived specifically for running, therefore it does not work well for cycling, or walking for that matter. The same way Cadence, I feel, would not work for running —and probably walking.As a designer, a cyclist and a below-knee amputee I can say that having a foot at the end of a cycling prosthetic leg is a waste of time, material, power and control. After trying many legs with feet, I have been using a cycling leg (designed by Erik Schaffer from A Step Ahead Prosthetics in Hicksville, NY)  for a few years now, and can say that with certainty. For reference, here's a photo from a 110 mile race I finished in May (6,000 feet elevation gain): http://www.flickr.com/photos/6... cycling prosthetic is much lighter, stronger and more aerodynamic than my natural leg. By eliminating the foot the designer took care of the all the problems described here (ankle being too stiff; difficulty seeing the pedal; cycle dead-zone and unclipping torque), while adding the benefit of directly driving power to the pedals... I see my legs as equipment, not body parts, which were designed to excel at specific tasks, very much like a golf club, a fishing rod or the right running shoes.

    As a conceit the Cadence is gorgeous, I love the exposure it gives to amputee athletes and I recognize the hard work behind this accomplishment. In the real world however, I'm afraid, it doesn't have a leg to stand on.