Reebok and MC10 have developed CheckLight, a soft, flexible skullcap that uses sensors and electronics to measure the force of impacts to the head and indicate severity through LED lights. Embedded in a stretchy material are an accelerometer and gyroscope that analyze linear and rotational forces of impacts. Sophisticated algorithms then determine the severity of the impact, activating green, yellow or red lights. This provides an objective measure of impact severity to inform treatment decisions and avoid long-term health effects from repeated head impacts. By making high-performance electronics stretchable and conformal to the head, CheckLight can provide new insights into head injuries during sports and activities.

1. 56
WEARABLE ELECTRONICS
Did I Just Hit My Head?
How Hard Did I Hit My Head?
By Mark Shortt
Wearable, high-performance electronics offer a new tool for real-time assessment of head injuries
The skullcap is made of a typical apparel
knit material, “a polyester material that’s
got some Lycra in it,” said Litchfield. “It
stretches, it’s comfortable, it’s low profile.”
Photo courtesy of Reebok.
Paul Litchfield, vice president of Reebok’s
Advanced Concepts Group, is on a roll as
he leans into the conversation at a small,
circular table in Booth 26718 of the
Las Vegas Convention Center’s South
Hall. It’s nearing 11:30 on a Thursday
morning in early January, the 2014
International CES is in full swing,
and Advanced Concepts’ booth
is teeming with visitors eager to
learn more about Reebok’s Check-
Light™ impact indicator, winner
of the 2014 International CES
“Best of Innovations” Design and
Engineering Award in the Health
and Fitness category. Suddenly,
Litchfield stops in mid-sentence. His
colleague, CheckLight Program Direc-
tor Paul Davis, is telling him that they
need to catch a ride to The Venetian—
where the CheckLight’s been on display since
Tuesday—in a few minutes.
“This is pretty interesting for us,” Litchfield
says afterward, referring to Reebok’s beehive
of a booth in this, their debut as an exhibitor
at CES. “We’re the Advanced Concepts Group;
we’re not booth people, and so this is a whole
new kind of endeavor for us.”
People are eager to talk with Litchfield because Reebok, the
iconic sports and fitness brand, and MC10 Inc., a bold, venture
capital-backed startup seeking to change the way we think about
electronics, have brought to market a product that could help
spur the development of an entirely new class of wearable elec-
tronics. The two companies began collaborating four years ago
with the intention of combining Reebok’s design capability with
MC10’s leading edge conformal electronics platform, a trove of
intellectual property that makes high-performance electronics
more wearable by reshaping what have traditionally been rigid,
boxy structures into extremely thin systems that can stretch,
bend, and flex with the natural contours and movements of the
human body.
Their partnership led to the release last July of CheckLight, a
soft, flexible skullcap with integrated motion sensors that measure
the force of impacts to the head with a high degree of accuracy.
The sensors are embedded in a stretchable plastic material and
work in conjunction with an array of electronic componentry,
including flexible metallic interconnects that
are linked to a microprocessor as part of a
system that analyzes, stores, and commu-
nicates crucial information about the
severity of head impacts. CheckLight
uses sophisticated algorithms to ana-
lyze and interpret the impact data,
indicating the severity of a blow
to the head via the activation of
a green, yellow, or red LED light.
“CheckLight takes the guess-
work out of identifying how hard
you just hit your head,” said Litch-
field in an interview at CES. “And
that’s super important because if
you and I were downhill skiing right
now, and you come across me and
I’m flat out in the snow, and you’re
like, ‘Hey, Paul, you fell—are you OK?’
And I’m like, ‘Yeah, my knee is OK, my
ankle and my shoulder are OK. Did I hit my
head? How hard did I hit my head? Am I OK?’
And so what CheckLight does is it takes the
guesswork out of trying to assign a force value
to the impact that just occurred to your head.
That might seem like a simple statement, but
it’s incredibly powerful, and it was the missing
part that we focused on when we began to re-
ally explore the notion of this CheckLight product.”
It’s important to eliminate the guesswork, Litchfield said,
because when people sustain blows to the head, they’re often
not aware of the severity of the hit and, therefore, may not seek
treatment. Many choose not to talk about symptoms, believing
that they will eventually subside without any ill effects. Although
it’s not a diagnostic tool, CheckLight communicates an objective
measure of the force of impact to let people know whether or
not they need to be assessed by a physician. The goal is to get
people on a quicker path to assessment, diagnosis, and medical
support or treatment.
The product launch coincides with a growing conversation
in the national media today about the health consequences of
concussions and traumatic brain injury, including those resulting
from sports-related activities. When Litchfield was growing up,
the idea of “getting your bell rung” was viewed as no big deal; it
was just a matter of shaking it off and getting back in the game.
“That was the standard operating model,” he said. “These

3. 58 DESIGN-2-PART magazine • May 2014
days, we’re finding out that that’s not the
right way to go. So, as the medical com-
munity is learning more and more about
head injury and its acute and chronic
long-term ramifications, we’re saying
that, with CheckLight, any time you get
a yellow light, or any time you get a red
light, just get yourself checked. It can be
really informal, but just make sure you get
checked. You shouldn’t ignore impacts to
your head at a moderate or a severe level.
For as tough as these young athletes are,
there are certain parts of our body that
you don’t want to get injured, and I think
your brain is one of them. So it’s really
important to be informed.”
How CheckLight Works
CheckLight ™
, designed for athletes of
all ages and skill levels, is described by Ree-
bok officials as the first impact indicator
that comfortably fits wearable electronics
directly on the athlete, rather than on the
athlete’s protective equipment. The key
to it all is MC10’s conformal electronics
platform, which accomplishes what flat,
inflexible circuit boards cannot—con-
form to the curves of the human body
in a way that doesn’t distract the wearer.
The skullcap is made of a typical
apparel knit material, “a polyester ma-
terial that’s got some Lycra in it,” said
Litchfield. “It stretches, it’s comfortable,
it’s low profile.” The electronics are pack-
aged up with a thermoplastic urethane
(TPU) material with a rubber-like feel.
“It stretches, it moves, it’s compliant, it’s
waterproof,” he said. “So the outer shell
is a very, very soft and supple plastic that
creates a waterproof environment, but
also creates a low-profile, very comfortable
overall product.”
Litchfield described CheckLight as “a
kind of New Age skullcap” that’s intended
for both contact and non-contact sports
and activities, including those in which
participants traditionally don’t wear
helmets. The product has been tested
on athletes participating in a wide range
of sports, including football, boxing, ice
hockey, lacrosse, and rugby. “It’s used in
everything from professional team sports
all the way through to individual sports,
from cycling and skateboarding to snow
sports and motor sports,” he said.
Embedded in the skullcap is a piece
of electronics that has a little tip and a
tail. The tip goes inside a little sleeve on
the skullcap, and the tail fits into a little
pocket that hangs down the back of the
wearer’s head. “When you put the skullcap
on, the tail of the product hangs down
beneath the helmet right in the back of
your neck, and the tip goes right up, with
the accelerator and gyroscope on it, right
behind your left ear,” said Litchfield.
A system of green, yellow, and red LED
lights alerts the wearer and those around
them to the severity of head impacts.
When the green light is on, it means that
the device is on and functioning; you have
not sustained a moderate or severe hit.
The yellow light activates when you incur
a moderate level hit, and the red light in-
dicates a severe hit. Litchfield said that the
hit criteria used by CheckLight are based
on the same head injury criteria from
Wright State University that are used by
the National Transportation Safety Board.
“Much like a traffic signal, if it’s green,
it’s go; you’re all set. If it’s yellow or red,
it’s caution and stop,” he explained. “And
so the yellow and red lights are intended
to make sure that you get assessed—get
yourself on a pathway, whether you’re
with friends doing something casually,
or whether you’re in a formal, organized
sport. Make sure you have the coach,

4. 59May 2014 • www.d2pmagazine.com
your parents, the trainers, or whoever,
just check you out. More often than not,
you’re going to be fine, but if you’re not
fine, you really should get on the pathway
to assessment and recovery as quickly as
possible.”
CheckLight measures more than
straight-on impact, according to Litch-
field. Inside the device are an accelerom-
eter, which measures acceleration and
deceleration that occurs linearly, and a
gyroscope, which measures acceleration
and deceleration rotationally. Both are
needed, Litchfield said, because a linear
force of impact—a straight-on hit to the
forehead, for example—causes a different
type of injury from that caused by a rota-
tional force of impact, such as a glancing
blow to the temple.
“By putting both of these devices in
there and by having them activate at the
same time, it makes this a much smarter
device because it will consider, electroni-
cally, both the linear aspects and the ro-
tational aspects of an injury and ‘bucket’
that output in the appropriate value,”
he said.
Once the gyroscope and accelerom-
eter are activated, the device looks at the
peak activation, it looks at the time of
activation, and it then calculates where—
based on nine locations around the
head—the hit has come from. CheckLight
employs sophisticated algorithms that ac-
count for the fact that head impacts are
absorbed differently in different locations:
A person’s neck and supporting muscu-
lature, for example, may allow them to
absorb more impact in a straight-on hit to
the head than they’d be able to absorb in
a blow to the temple, which would likely
involve a rotational force. “The device is
super smart and the algorithms are super
sophisticated,” said Litchfield.
Innovative Design Features
MC10, a Cambridge, Mass.-based start-
up whose investors include North Bridge
Venture Partners, Braemar Energy Part-
ners, and Medtronic, among others, is on
a mission to “extend human capabilities
by making high-performance electronics
virtually invisible, conformal, and wear-
able.” The company’s handiwork, based
on the stretchable electronics platform
of technical co-founder John Rogers, a
professor of engineering at the University
of Illinois, Urbana-Champaign, is evident
in CheckLight’s unobtrusive form and fit.
“What’s really innovative about the
product is that we designed it to be, es-
sentially, transparent when you use it,”
said Litchfield. “When you put this on,
all you feel is your traditional skullcap
underneath your helmet. You can’t feel
the device; it just essentially becomes
invisible when you use it. And what’s re-
ally cool about it is that it’s very apparent
and very evident when it works. So there’s
a transparency in its fit and form, but its
effectiveness is absolutely apparent.”
Another important aspect of the de-
sign is that CheckLight is not intended
solely for football or for ice hockey, or for
lacrosse or baseball, he said. It’s not a de-
vice just for bicycling, or snowboarding, or
for skateboarding or equestrian events, or
for motorsport events like motocross. “It’s
really a device for all of them,” he said.
“What’s great about it is that it’s designed
in a way to be universally available to any
sport or activity you’re doing.
“The other thing that’s really cool
about this device is that it will retain, in its
memory, the number of yellow and red
hits that you’ve incurred,” he continued.
“And in the growing body of knowledge in
the medical community, it seems there’s

5. 60 DESIGN-2-PART magazine • May 2014
By embedding MC10’s conformal electronics
into the skullcap in a way that’s not
distracting to the athlete, CheckLight can
provide information on the severity of
head impacts that hadn’t been available
previously. Photo courtesy of Reebok.
a direction heading towards being
concerned about the number of
hits you take over a long period
of time. So this device will actually
measure those outputs and keep a
record of those outputs.”
The genesis of what is now
CheckLight goes back about four
years, when Litchfield and Check-
Light Program Director Paul
Davis were aware of a small and
growing conversation about head
trauma and were determined to
get involved. They were interested
in finding ways to help reduce the
incidence of concussions.
“We quickly found out that
the only way [to stop them from
occurring] is to have people stop
playing anything and stop moving
around, and that’s not realistic and
it’s kind of silly,” he remembered.
“So then we started talking about
how we could get at more informa-
tion about impacts.”
That question got Davis, Litchfield, and their Advanced Con-
cepts team off and running, leading to what Litchfield called “a co-
lossal education” along the way. It’s been a profound learning ex-
perience, he said, not only
in the “absolute aspects”
of head impacts, devices,
and electronics, but also in
some of the “less than clear
issues” that currently exist
in the medical community
and elsewhere. “It’s been
an evolving process, both
from the background of
the head trauma issue and
from the device,” he said.
Litchfield is on the
board of directors of some
companies that were help-
ing with a particular prod-
uct that benefited from
conformal electronics.
Through networking, he
was able to hook Reebok
up with MC10.
“The collaboration
with MC10 has been great,”
he noted. “MC10 does flex-
ible conformal electronics, and they do it really well. It’s a super
talented group that came to the table with us; we kind of forged
this integrated team and we rolled forward as one group. MC10
provided the electronics backbone and we provided the form

7. 62 DESIGN-2-PART magazine • May 2014
factor, the design of the device. It’s a great relationship. The
MC10 crew is a very, very talented group.
“One of the things that we strive to do in Advanced Concepts
at Reebok is we strive to make sure we continually look out in the
world at people who are doing cool things that can help educate
us and challenge us in our thinking,” he said. “I’ve been working
at Reebok for about 28 years, and you can get pretty set in your
ways. And what’s super important is you’ve got to keep on chal-
lenging yourself to kind of think differently.”
A Potential Teaching Tool
Having been in development with CheckLight for about four
years, Reebok has tested the device on “hundreds of athletes in
a number of different test cycles,” and in a variety of sports, ac-
cording to Litchfield, who said that it’s been gratifying to know
that the product has already helped people.
CheckLight’s electronics are
packaged in a thermoplastic
urethane (TPU) material with a
rubber-like feel. Photo courtesy
of Reebok.

8. 63May 2014 • www.d2pmagazine.com
“In our testing methodology, some people have gotten yel-
low or red hits—not the big, open field, ‘knock ’em out’ kind
of hits, but just regular, in-play hits and contact,” he said. “And
they’ve been assessed and diagnosed and, most times, put right
back in the field of play. But a couple of times, people were
injured and they got the appropriate medical support right
away. And that allowed them to recover and get back on the
field of play sooner.”
Litchfield sees CheckLight as a potential teaching tool that’s
changing the way people participate in some of the high-impact
contact sports. The device is actually helping to reinforce safer
contact techniques by encouraging athletes to keep their heads
up and out of impacts. Because athletes will know that they’ll
have to come off the field if their yellow or red light goes on,
they’re finding ways to make sure their head doesn’t absorb the
biggest hits on the field.
“This is anecdotal; this is not the principal use of the device,
but, anecdotally, throughout our testing and throughout the use,
the people using CheckLight have been using it in a way that
they’ve taken their head out of their first contact because they
don’t want the red light to go off,” he said. “So what it’s doing is
it’s kind of changing the way people participate in some of the
high impact, contact sports, because you can still play well and do
a great job, and if your yellow or red light doesn’t go off, you’re
going to stay on the field. So it’s been kind of cool. Hopefully,
this will ultimately be considered as a potential teaching tool on
how to teach people to participate in these high velocity, high
impact, high contact sports, and for finding ways to make sure
your head stays out of the principal hits.”

9. 64 DESIGN-2-PART magazine • May 2014
CheckLight, designed to be worn by people partici-
pating in all types of sports and activities, is nev-
ertheless a natural for high-impact contact sports,
such as football and boxing. We sat down with
Paul Litchfield, vice president of Reebok’s Advanced
Concepts Group (RAC), earlier this year at CES in
Las Vegas, and asked him about the company’s
plans for CheckLight.
Q: Do Reebok’s target markets for CheckLight include
college football, the NFL, and professional boxing?
A: Yes, they sure do, and I suspect that those will be people
who endorse and support it, but I’m not sure that they
will be the first users of it. I actually think it’s going to be
people like you and me, with our families, with our kids, as
we are living our life. Professional sports are an interesting
perspective because these folks are getting paid to stay on
the field. Their careers, their income depends on it. They
also have multitudes of people looking at them at every
play. And so do college athletes. They’re being evaluated
all the time by the coaching staff, by the medical staff, by
the training staff. So they certainly could benefit from using
CheckLight, but I’m probably more concerned with help-
ing out the youth, the kids, the Dad doing soccer practice,
or a Mom doing hockey practice. The coaches can’t see
An Extra Set of Eyes for Coaches

10. 65May 2014 • www.d2pmagazine.com
all the plays, and they’re not there to be diagnostic of what
kind of physical maladies are occurring; they’re just trying
to help the young kids out.
And so CheckLight is a great tool to give them an extra
set of eyes, and to put a value to the impacts that may occur
that are going to occur anyways. That way, you can be just a
little bit more confident, and you can focus on the play, as
opposed to worrying about the health of the kid.
Q: What do you see as the company’s biggest challenge
in achieving broader market adoption of CheckLight?
A: We’re going to need, at the consumer level, just a mind
shift, and I’ll give you a couple of examples. When you and
I were growing up, did you ever wear a bicycle helmet or
a seat belt? No. I never did, either. They were available,
and yet nobody used them. But people have used bicycle
helmets more and more, and now, when you see somebody
riding a bicycle without a helmet, you’re like, ‘That’s kind
of strange.’ And seat belts, everybody wears them now. The
most recent kind of example I can give is in snow sports—
downhill skiing and snowboarding. Five years ago, you
would see a couple of helmets on some people, and you’d
assume they were ski racers. Nowadays, I bet on any ski hill,
there are probably 90 percent of the people wearing hel-
mets. So it’s basically a mind shift to people understanding
what the value of being informed about head impact can
provide. And we’re working real hard at that.
—Mark Shortt