"When I lay on the ground, I thought I had knocked the wind out of myself," says McClellan, a 56-year old resident of Rocklin, California, who will soon represent one of two US teams in the Functional Electrical Stimulation bike race at the world's first Cybathlon in Switzerland. "It feels like you're out of breath. I [thought of] lifting my legs up, there's supposed to be some relief in doing that when you've lost your wind. But when they lifted my legs up, that was a tell-tale."

McClellan spent about three months in the hospital. Having lost sensation in his lower limbs, he went through rehabilitative programs for people with spinal cord injuries. But he remained restricted to a wheelchair. It was only a couple of years later, when he found an experimental research program in Cleveland, that he was able to stand again.

A modified recumbent bike that Team Cleveland will use at the Cybathlon.

As a candidate of the program, which is a part of the Advanced Platform Technology (APT) Center at Louis Stokes Cleveland VA Medical Center, he went through an intensive 12-hour surgery to have a pulse generator implanted under his skin. The device is connected to an external control box that a research patient can activate with the press of a button. When activated, the implant sends electrical currents (1 milliamp or less) to electrodes wrapped around the femoral nerve in the thigh that fires up the muscles to move the hip and straighten the legs. The controlled stimulation allows people with severe spinal cord injuries to stand again.

"It's essentially a pacemaker for the skeletal muscle instead of the heart," says Ron Triolo, professor of biomedical engineering at Case-Western University and executive director of the APT Center. "Initially the system was designed for people paralyzed [from the] neck down so they could take a few steps again."

Now the team of researchers and engineers, led by Triolo, is using the implant to participate in the Functional Electrical Stimulation (FES) bike race at the Cybathlon. The group, also known as Team Cleveland in the competition, has found a way to modify off-the-shelf recumbent bikes so that the people riding them always know the position of the pedals. Based on that, they adjust the stimulation for the right intensity at the right time to make the paralyzed muscles create a pedaling movement in sync with the bike.

"We're the only team using an implanted approach to activating the paralyzed nervous system...I think we have a good chance of winning the competition." - Ron Triolo, director of the APT Center

For years Triolo has helped people with severe spinal-cord injuries walk again, but introducing biking into their lab routines last year has presented new rewards. Unlike the standing and postural experiments that tend to grow tedious, the program volunteers are instantly drawn to biking as a fun exercise. "It eliminates the whole issue of balance," says Triolo. "With biking, you don't have to support the body weight and the muscles can do what they're best at -- generating bursts of power."

With an entire discipline designed to bring in FES biking technologies from across the world, including a second American team called Myolyn from Miami, the small federally funded research team from Cleveland has its work cut out for it. But what it lacks in elaborate resources it makes up for with breakthrough research.

"Our secret weapon is the implanted technology," says Triolo. "We're the only team using an implanted approach to activating the paralyzed nervous system. The other 11 teams are still using electrodes applied to the surface skin, which tend to be a little less efficient, less selective and less repeatable than [our] technology. I think we have a good chance of winning the competition."

***

About seven and a half years after his accident in the Baja rally race, McClellan was back on a bike.

At the end of July this year, on an iceless skating rink at the City of Cleveland Heights Community Center, the team from Ohio held its own internal trials to find the fastest pilot for the Cybathlon. A couple of physical therapists helped McClellan, one of five participating pilots, slip into his recumbent bike. With his body close to the floor, and legs half bent in a pedaling position, they slowly dragged him onto an inclined ramp to build momentum. Just in time for the start, he pressed a button on a black, brick-size box in his hands. The muscles in his legs contracted and his feet started moving in tandem with the pedals as he took his first lap.

Five laps later, McClellan had the fastest time in the first half of the Cleveland trials. Before the next heat, he went over to check on Mark Muhn, his close friend and fellow research candidate who was a strong contender to win the race. But for most of his time outside the bike that day, McClellan sat motionless in his wheelchair in a distant corner of the rink. Dressed in a white tee and black tights, with his white earpods firmly in place, he had his eyes closed as if he were miles away on a pristine beach.

"If you were to ask me: 'What if you woke up tomorrow and all of a sudden you just stepped out of bed— would you regret the seven years prior?," McClellan would later say. "Honestly, the answer is, I wouldn't. Yeah, this has its complications and frustrations, for sure. But there's a whole bunch of pluses on the other side of it. There are tragedies and we all have them. It's all about attitude."

Michael McClellan at the Cybathlon trials in Cleveland, Ohio.

For the second and final heat in the race, McClellan slid back into the bike. He completed the first two laps faster than the other contenders, and even though his time trailed off in the remaining three, he went on to win the first spot.

McClellan, who runs a construction company in California, will represent Team Cleveland in the FES bike race at the Cybathlon. In the event that he's unable to participate on the final day, Muhn, who came in second at the trials, will be in Zurich to take his place. "I did well enough to be the runner-up," says Muhn. "Michael's ahead of me. He knows that I don't wanna knock my friend out of first place but if I have a chance, he's getting knocked out. He knows that I'll do it and he knows that I love him."

The relationship between the two pilots, which started before McClellan introduced Munn to the program four years ago, is one of camaraderie and friendly competition. It's the kind of support system that is known to aid recovery from a life-changing event.

***

At the end of a family ski trip in Tahoe, Mark Muhn went on a last ski run with his wife and kids. An avid skier, he decided not to wear his helmet for the casual run. As he playfully went down the hill, his skis got caught under a tree root in the ground that threw him head first toward a boulder.

"I can still see that frozen moment in time," says Muhn. "I'm flying above the ground, I see the boulder coming and I can't get my hands up fast enough to protect my head. Next thing I know, I was laying on the ground. I think that I'm hanging from a ledge because I have no feeling whatsoever going to my arms. I can't feel my clothes. And if you can't feel your ski boots you're not feeling anything. I'm trying to claw back up, there's the feeling that I'm not touching anything. I think I need to pull myself up, when I hear Carol saying: 'Your head is bleeding. You need to hold still.' And I tell her I need to pull myself up. She says: 'You're flat on the ground.'"

"Any recovery you can get in the early days, you get to keep. ... My toes wiggled at two-and-a-half months and I told everybody. Eight years later, that's all I have." - Mark Muhn, Team Cleveland runner-up pilot

Muhn's C7 vertebra was crushed at the base of his neck. He lost control of his lower body but would also live with chronic pain and numbness in his hands and elbows. As Triolo would later point out, Muhn is one of the few program participants with double implants so he can have 24 channels of stimulation for the extent of his spinal-cord injury. McClellan, like most others in the program, has a standard 16-channel stimulator that fires up just enough for people with more control of their upper bodies.

After his accident, Muhn spent about 45 days in the hospital. At first, when the doctors tried to put him through intense physical therapy, he did not feel motivated to move at all. He needed to push himself to regain some movement but he remembers wanting to stay on his back, unwilling to try.

Now, eight years later, he wishes he had known the importance of the smallest initial movements. "Any recovery you can get in the early days, you get to keep," he says back at his home in Morgan Hill, California. "The first few weeks are really difficult. What you get in 90 days is probably all you're gonna get. My toes wiggled at two-and-a-half months and I told everybody. Eight years later, that's all I have."

He now uses his experience to offer support to people in similar situations. Muhn often responds to calls from people who are looking to connect recently injured people with someone like him, who has adjusted to a new reality. "When I hear a story about somebody new," he pauses as his eyes well up and his chin starts to quiver, "It crushes me. I know I have a new brother ... I know what he has to go through. It's a hard realization to know that your life is never going to be the same."

Michael McClellan (left) and Mark Muhn (right) at the Cybathlon trials in Cleveland, Ohio.

Muhn acknowledges the challenges that he faces on a daily basis but he doesn't let them get in the way of his life. Having been a carpenter for decades, he continues to run a construction business with 10 active sites that he oversees on a powered wheelchair and a forklift equipped with hand controls. He makes time to go to the beach and even goes dancing with his wife, Carol. And now, even though he isn't the primary pilot in the race, he has been exercising on a bike along with McClellan. The two spent a month training at Muhn's farmhouse in Morgan Hill.

Going to the Cybathlon together, as competitors and close friends, has multiplied the motivation for both pilots. As soon as the sun would begin to set in Morgan Hill, McClellan and Muhn could often be found pedaling on their recumbent bikes parked outside on a green patch of land. The stationary warm-up is part of the training routine that the two devised to be in top shape for the final race. An hour or so of pedaling later, they would bike around the streets and down the hill as Carol followed them in a large black truck.

"It doesn't feel like I'm really biking. But I'm doing something. It gives me a feeling of purpose." - Michael McClellen, Team Cleveland pilot

"When I'm on the recumbent bike, in comparison to having ridden before my injury, the feeling is similar in that my energy is pushing me forward," McClellan says back at Muhn's house. "It doesn't feel as good as before when I was on a bike. It doesn't feel like I'm really biking. But I'm doing something. It gives me a feeling of purpose. I don't know where that falls on the scale, but it's right up there."

Training on the bike every day for the Cybathlon has helped restore a lifestyle that bears some semblance to McClellan's active days. But the exercise has done more than just activate his muscles. It's helping him fight the demons that reveal themselves in everyday situations.

"When I go to the theater, in the intermission, when everyone is drinking wine, having cheese and crackers, they're all standing. All of a sudden, I'm down. That's when you start to feel any sense of insecurity or inadequacy," McClellan says. "That feeling is the complete opposite of getting on that bike and riding on that track."

This is the second episode in a five-part video series called Superhumans, which follows the Cybathlon from start to finish. Watch out for the next episode on Tuesday, Sept. 27th, right here on Engadget.