IEEE Spectrum January, 2016 - 33

Matter of fact
In the early 1780s, Italian anatomist Luigi Galvani discovered that he could make
a dead frog's leg muscles contract by sending an electric current through a nerve.

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.
t r io l o o r igi n a l ly c o n s i d e r e d 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 para-
lyzed 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 com-
pensate 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 con-
tractions 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 biol-
ogy 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 elec-
trical 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
Outside And in:
have one more thing to do. He'll press the
The stimulator's pat"stand" button on his controller and rise to
terns are selected
his feet to receive the gold medal.
using external controllers, and its programHe may take the podium as a modern marvel,
ming is changed via an
but
McClellan says the process of becoming a
external transmitter
cyborg Olympian has only whetted his appe-
[left] . The implanted
pulse generator sends
tite for more. "My enthusiasm comes from
current through thin
realizing:
This is just the beginning of what
wires that stimulate
we can do," he says. -Eliza Str ick l a nd
the nerves [right].

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Table of Contents for the Digital Edition of IEEE Spectrum January, 2016
