Michael McClellan flashes a thumbs-up sign as he speeds by on a recumbent tricycle, breathing hard but smiling behind dark sunglasses. He pedals along a paved path that loops through a leafy park in Cleveland, passing office workers enjoying alfresco lunches on a warm June day. They chew their sandwiches, oblivious to the guy on the trike. They have no idea that McClellan is paralyzed from the waist down, and that they’re watching something extraordinary. It’s a training session for one of the world’s first competitive cyborg cyclists.
McClellan is preparing for the Cybathlon, the first ever cyborg Olympics, coming to a stadium in Zurich in October 2016. In these games, the competitors will use advanced technologies to compensate for disabilities like paralysis and limb amputation. In the cycling race, for example, paraplegic competitors will use electrical stimulation systems to jolt their paralyzed legs into action; electrodes and muscles will work in tandem to propel their trikes forward.
Yes, the Paralympics already offers athletes with disabilities a forum to showcase their talents. But the Cybathlon’s rules and aims are different, explains organizer Robert Riener, a professor at the Swiss Federal Institute of Technology in Zurich (ETH Zurich). The Paralympics bans motorized equipment, but the Cybathlon embraces it.
“It’s less about force and speed, and more about control of the body and the device,” Riener explains. Instead of celebrating the human body moving under its own power, the cyborg games will celebrate the strength and ingenuity of human-machine collaborations. That’s why the Cybathlon’s competitors won’t be called “athletes” but rather “pilots.” Each team consists of a technology group and a pilot, and both will be honored if the team wins a medal.
Riener, who develops robotic rehabilitation systems at ETH Zurich’s Sensory-Motor Systems Lab, says the Cybathlon grew out of his frustration with the assistive technologies currently available to people with disabilities. “Most of them are not very useful for the patient,” he says. For example, only a quarter of all people with arm amputations use prostheses, Riener says, because the devices are poorly suited to the routine tasks of daily life.
By inviting engineers from academia and industry to build new technologies and train pilots for the Cybathlon, Riener hopes to spur innovation. And to ensure that the resulting gear will be useful beyond the context of the stadium, the Cybathlon’s events will incorporate those routine tasks of daily life. In the race for people with powered leg prosthetics, pilots will climb stairs and walk across stepping-stones. During the obstacle course for amputees with powered arm prosthetics, the pilots must slice loaves of bread and open jars of jam, ordinary breakfast rituals that become exasperating when attempted one-handed.
The 80 teams expected at the Cybathlon will arrive in Zurich from all over the world. There will be coverage by the BBC and Japan’s NHK, among other major networks, and if the games are a hit, the next Cybathlon could take place in Tokyo in conjunction with the 2020 Summer Olympic Games.
Ponder that for a moment. The world’s premier athletic competition could include the marathon, 400-meter freestyle swimming, the high jump, and also events where participants wrestle the lids off jam jars and climb flights of steps. But at the Cybathlon these seemingly mundane feats will be recognized for what they are: a remarkable synthesis of engineering, dexterity, and pure human grit.
“I like speed.” McClellan huffs as he speaks, breathing hard after his laps around the park. “That’s the reason why I’m in a wheelchair.”
While tearing along on a dirt bike in Mexico in 2009, McClellan didn’t quite clear an unexpected gully that spanned the road. The bike’s impact with the trench’s far wall jammed his body against the seat and shattered a vertebra in his lower back. The shards of bone pressed into his spinal cord, making it resemble “a garden hose with a kink in it,” McClellan says. His legs weren’t injured, but movement commands from his brain can’t pass through the damaged spinal nerves to reach them.
How, then, can this paralyzed man cycle through a Cleveland park? The answer comes from a lab in the Louis Stokes Cleveland VA Medical Center, across the street. Neural engineer Ronald Triolo runs the Advanced Platform Technology Center there (he’s also a professor at nearby Case Western Reserve University). Triolo uses a technique called functional electrical stimulation (FES) to help people with spinal cord injuries, deploying pulses of electricity to activate the leg nerves that control otherwise dormant muscles. These jolts crudely mimic the electrical signals that would normally travel from the brain and through the spinal cord to reach the peripheral nerves.
Many rehab clinics have simple FES systems with surface electrodes that stick to the user’s legs, stimulating the nerve faintly by transmitting an electric pulse through skin and flesh in the correct general direction. But this scheme doesn’t provide precise control, so Triolo has pioneered the use of electrode “cuffs” that are surgically implanted and wrap around the nerves themselves.
Each tiny cuff of silicone rubber has four embedded platinum contacts that touch different spots on the surface of a nerve bundle, allowing stimulation of specific nerve fibers in intricate patterns. The current arrives at the electrodes through thin wires connected to an implanted pulse generator that sits inside the abdomen. Triolo designs stimulation patterns in his computer and sends the commands to the pulse generator via a wireless link. “All the changes to the timing and patterns of stimulation are made in software, so none of the implanted components have to be replaced,” he explains. An external device also transmits energy via radio frequency to recharge the pulse generator, so there’s no battery to swap out.
Through two decades of experiments, Triolo has developed stimulation patterns that enable paraplegics to do leg lifts, rise from their chairs, stand upright and support their weight on their legs, and even take small steps forward while maintaining balance with a walker. He’s now working on nerve cuffs with additional embedded contacts that will let him program more sophisticated stimulation patterns. Ultimately, he wants to get people like McClellan walking normally again.
McClellan heard about Triolo’s experiments in 2011 from a friend at a rehab clinic near his home in California and immediately volunteered. “I didn’t think twice about it,” he says. “I was all in.” During an 11-hour procedure, surgeons implanted 10 electrodes in his legs and hips: a cuff around each of his two femoral nerves, allowing control of discrete muscle fibers in his quadriceps, and eight simpler single-contact electrodes that activate the nerves in his gluteal muscles and hamstrings. After six months of healing, McClellan came back to Cleveland to have his stimulator turned on for the first time.
He didn’t jump to his feet right away; first a team of physical therapists put him through eight weeks of grueling strength training. He spent hours lying in bed as the stimulator energized his nerves and caused his legs to lift, hoisting small weights into the air. Though McClellan’s muscles were triggered by externally generated pulses rather than his brain, the result was nevertheless the same: Muscle mass increased. In between these training sessions, the engineers tested different stimulation patterns on him, experimenting with the amount of current and the timing of the electric pulses. Then they built a small external controller with a few buttons, and programmed each button to trigger a stimulation pattern for a specific movement, such as lifting his left leg or rising from a chair.
Finally, the clinicians and engineers agreed that he was ready to stand. With the whole team gathered in a rehab room, McClellan punched the “stand” button, and his paralyzed legs hoisted him upright. Asked to describe that moment, McClellan pauses.
“Have you ever seen a dog do a big stretch with its paws out in front of it?” he says at last. “You see it and you think, ‘That’s gotta feel good.’ ” The researchers who watched him extend his nearly 2-meter (6-foot-4-inch) frame must have thought the same thing.
Triolo originally considered the Cybathlon a bad idea. “What we really need is cooperation and international groups working together, not a competition,” he remembers thinking. But he soon reconsidered, deciding that the games could push the technology forward by bringing researchers together in a spirit of friendly rivalry. Intrigued by the cycling event, he asked several of his research volunteers, including McClellan, if they’d help him adapt his stimulation system for cycling, and got to work on new patterns that would cause a paralyzed cyclist’s leg muscles to push on bike pedals.
Now, in this early-summer training session in the leafy Cleveland park, a rejiggered system is getting its first tryout. The engineers have already spent hours with McClellan on a stationary bike in the lab, fine-tuning the stimulation pattern. In the park, though, they’re discovering the limitations of their current setup.
As McClellan pedals up a subtle rise in the path, the trike naturally slows down, but the timing of the muscle-stimulation pulses in his legs doesn’t vary. That’s a problem, because McClellan gets out of sync, with his leg muscles pushing against the pedals at the wrong points in their revolutions. McClellan tries to compensate by using a few muscles he can control around his hips to bear down at the proper moments. He tries to pull each hip up “just enough to get the pedal around that 12 o’clock point, to get it ready for that power stroke,” he explains.
Triolo has a plan to improve the translation of McClellan’s muscle contractions into cycling forces. He’ll spend the next few months adding position sensors to the pedals that will send information to McClellan’s implanted pulse generator, signaling each moment when a pedal is ready for its power stroke. “The trick is getting the technology and the biology to work together as a single unit,” Triolo says.
While McClellan’s first task as a pilot is pressing the button on his controller that triggers the cycling stimulation pattern, that’s hardly the end of his involvement. His muscles must respond to the electrical stimulation and do the actual work, and if they’re not in good condition his performance will quickly decline. Stimulating a nerve once muscle fatigue has set in yields diminishing returns, Triolo says.
To improve both strength and endurance, McClellan will keep doing leg lifts at the gym and hopes to get a recumbent trike to ride in his neighborhood. He’s eager to train, and not only for the Cybathlon. He’s also thinking of his future, and dreaming of stem-cell therapies that could one day repair damaged spinal nerves. Such treatments are just laboratory experiments today, but if they become medical realities McClellan plans to be strong enough to benefit. “I want to have healthy muscles and good bone density so I can participate in anything that comes along,” he says.
Next October, if all goes well with his training, McClellan’s healthy muscles will whiz him around the 750-meter track in Zurich. If his body and his technology work together to speed his bike across the finish line first, he’ll have one more thing to do. He’ll press the “stand” button on his controller and rise to his feet to receive the gold medal.
He may take the podium as a modern marvel, but McClellan says the process of becoming a cyborg Olympian has only whetted his appetite for more. “My enthusiasm comes from realizing: This is just the beginning of what we can do,” he says.
This article originally appeared in print as “Cyborgs Go for Gold.”