It is half bicycle, half-elliptical machine -- presto, it is an ElliptiGO.
You hop on like a bike, but instead of pedaling, you're running motion provides the power.
"With a bike, you're kind of spinning your wheels, if you will. With the ElliptiGO it is more of a running motion. So, if you just emulate running, that is what an ElliptiGO is like. So it is quite a bit different than a bicycle actually, but as far as a crossover sport to running, it is almost exactly like running," says Karnazes.
The benefits of an ElliptiGO are no saddle sores from long bike rides and no knee, back, or ankle pain from running.
"You can get on an ElliptiGO and experience the joy of running, being outside, and not have the associated pounding," says Karnazes.
Karnazes is the ultimate runner. He once ran 82 consecutive hours, did 50 marathons in 50 days, and now he is riding his ElliptiGO from San Francisco to Los Angeles. That will be 500 miles in five days, arriving just in time to run Sunday's L.A. marathon.
"I think the bottom line is I'm just too cheap to spring for airfare so I'm going to ride down there instead," says Karnazes.
The ElliptiGO right now is about $2,000, but the company hopes to soon get that down to $1,000 for consumers.