IEEE Spectrum October, 2007 - 6

CRUNCH: Accelerometers in helmets
[inset] measure the potential of hits
like this to cause brain injury.

SImbEx (2)

of physics. The device would provide, for
the first time, a data set large enough
for researchers to understand when a
concussion is likely to have occurred,
according to how hard a hit was and to
which part of the helmet. Armed with
that knowledge and real-time data from
the helmets, sideline staff will know
when a player should be brought off the
field for neurological tests.
The Head Impact Telemetry (HIT)
System developed by Simbex, of
Lebanon, N.H., combines six strategically positioned MEMS accelerometers,
a temperature sensor, a wireless transceiver, nonvolatile onboard memory, and
a nickel-metal-hydride battery pack in a
halo that fits inside a helmet. The package allows the spring-mounted accelerometers to sit right up against a player's
head, so the movement of the skull is
measured instead of the movement of
the helmet itself. It adds just 170 grams
to a 1- to 2-kilogram helmet's weight
and does not significantly alter its fit.
The system automatically generates
a data report when any single sensor
detects an acceleration that exceeds

www.spectrum.ieee.org

10 gravities. The report
impact history, to remove players before
includes 12 milliseconds
they get seriously injured," says Simbex's
of data from before the
director of engineering, Jeffrey J. Chu.
system is triggered and
Duke University neurologist Joel C.
28 ms following the instant
Morgenlander, who recently joined the
of impact. A controller
NFL's brain injury committee, thinks
connected to a laptop on
this is a good idea. "The medical decision
the sidelines receives this
has to be separated from the heat of the
information wirelessly.
moment," he says.
An early version of the
Stefan Duma, a professor of mechaniHIT system was introcal engineering and director of Virginia
duced during the 2003
Tech's Center for Injury Biomechanics,
football season: four footsays getting even greater numbers
ball players from Virginia
of players outfitted with the device
Polytechnic Institute and
is important because there is "great
State University, in Blacksburg, Va.,
potential for prevention of brain injuwere monitored through 35 practices and
ries, but the lack of scientifically sound,
10 games. Researchers recorded roughly
evidence-based studies is a barrier to
3300 head hits and found that, on averimproved prevention and treatment."
age, players endured 50 impacts strong
The data already collected have been
enough to trigger the system during the
enough to demonstrate that, contrary to
course of a single game. The average
conventional wisdom, most impacts that
acceleration caused by those hits was
result in concussion occur on the side
40 g's per blow, the same level of impact
of the head rather than the front or the
delivered by the gloved fist of a profestop. Riddell Sports Group, in Rosemont,
sional boxer. At least twice a game, the
Ill., which makes helmets for the NFL
players took shots to the head with
and dozens of college teams, has already
forces on the level of a car crash. The
responded with a new helmet design,
data reports include parameters such as
called the RevolutionT, which extends
the Gadd Severity Index (GSI), a method
farther down the jawline and includes
developed by automobile crash research- the same kind of shock-absorbing paders for describing just how jarring a blow ding near the jaw that is found in the
someone has received. A human head
helmet's crown. Previously, the only
can withstand GSI values as high as
purpose for the padding on the side of
1000 without serious injury; the blows
its helmets was to improve the fit.
endured by the Virginia Tech players
Asked if the NFL had any plans to
ranged from 1 to 1599.
use the HIT System or to make Riddell's
Simbex, working with researchers
new helmet a required part of every
at engineering and medical schools at
player's uniform, league spokesman
Virginia Tech and Brown University, in
Greg Aiello noted that each player gets
Providence, R.I., improved the comto choose the type of helmet he wears.
munication system, allowing as many
As for the monitoring system, Aiello
as 64 players to be monitored simultasays the league's Committee on Mild
neously with a single controller on the
Traumatic Brain Injury (MTBI) is cursideline. In 2004, nearly 500 players at
rently reviewing it but would offer
five colleges-including Virginia Tech;
no details regarding when the review
the University of North
would be completed or
Carolina, Chapel Hill;
whether the group had
and the University of
reached any preliminary
Oklahoma, Norman-
conclusions.
wore the device in their
For its part, the NFL
helmets throughout the
has been sponsoring
season. Simbex says
studies aimed at quanti15 schools will take to
fying on-field collisions
the field this fall with the
using methods other
HIT System, capturing a
than the HIT System.
snapshot of the forces at
Chris Withnall, a senior
play in each tackle.
engineer at Biokinetics
With a large data
and Associates, in
set from on-field colliOttawa, conducted studsions, "we may be able to
ies on behalf of the NFL
SHOCK ABSORBER: The inside of
develop predictive algothat used video footage
this helmet is outfitted with a wireless sensor system by Simbex.
rithms, using a player's
from games to recon-

October 2007 | IEEE Spectrum | NA 11

http://www.spectrum.ieee.org

Table of Contents for the Digital Edition of IEEE Spectrum October, 2007