After taking a look at the Jet Blade hydroplaning watercraft last week, we were alerted to another senior design project from Calvin College, Michigan. A different group of students has designed and prototyped a device they're calling the TheraTryke. Aimed at those with MS, spinal cord injuries, or complete paraplegics, it lets riders use their hands, feet or a combination of both together to propel themselves forward.
Intended as both a therapeutic and recreational vehicle, the TheraTryke gives those with limited or no use of their legs a fun way to get outdoors and get some exercise and get both the upper and lower body moving. Even if the rider only uses their arms, the recumbent bike moves the lower body around and exercises legs that would otherwise spend most of their time motionless.
Many paraplegics and those with limited leg function try to find ways to continue exercising their lower body – exercise and stretching is said to help cut down on the spasm and muscle atrophy issues that tend to develop when limbs aren't able to be moved. Also, if you're hopeful that your paralysis may one day be cured, you can see how you might want to keep your legs in the best shape possible.
The TheraTryke is designed to help in this regard, diverting some of the power from its hand crank to pump the rider's legs around in a cycling motion. It's like a manually operated, outdoor exercise centric version of something like the RT300 rehab therapy system – although the RT300 also incorporates electric muscle stimulation to tone muscle.
Theratryke will likely be a fairly challenging machine to ride if only relying on hand power. Regular handcycles can be quite tough to get up a hill as it is, because riders can't stand up on the pedals and use their body weight in the same way you can on a regular bike. Theratryke's design diverts about a third of the pedaling power to moving the legs, so it's going to be hard work without some help from the lower body. However, gearing that enabled riders to power the vehicle by hand strength alone were one of the requirements the team set themselves.
Theratryke uses a Shimano Nexus 7 gearing system that enables continuous gearless ratio changes controlled by a hand dial. But the ratio of hand turns to leg turns appears to be fixed – one paraplegic we ran the idea past suggested that the trike might be more of an attractive option for her if it was possible to lock the legs when the going gets tough.
The Calvin College team will be taking their TheraTryke to a hospital in the Grand Rapids area for feedback on the design. For a fully detailed proposal on the TheraTryke, as well as engineering information and a business case, check out the Final Design Report (PDF) at Calvin College Engineering.