Develop New Way to Measure Effect of Head Hits in
WFMY News 2
WINSTON-SALEM, N.C., July 18, 2013 -- Scientists at Wake Forest Baptist
Medical Center have developed a new way to measure the
cumulative effect of impacts to the head incurred by football
The metric, called Risk Weighted Cumulative Exposure (RWE), can
capture players' exposure to the risk of concussion over the course
of a football season by measuring the frequency and magnitude of
all impacts, said senior author of the study Joel Stitzel, Ph.D.,
chair of biomedical engineering at Wake Forest Baptist
and associate head of the Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences.
The study is published in the current online edition of the Annals of Biomedical Engineering. Based on data gathered throughout a season of high school
football games and practices, the researchers used RWE to measure
the cumulative risk of injury due to linear and rotational
acceleration separately, as well as the combined probability of
injury associated with both.
"This metric gives us a way to look at a large number of players
and the hits they've incurred while playing football," Stitzel
said. "We know that young players are constantly experiencing
low-level hits that don't cause visible injury, but there hasn't
been a good way to measure the associated risk of
Concussion is the most common sports-related head injury, with
football players having the highest rate among high school
athletes, according to the study. It is estimated that nearly 1.1
million students play high school football in the United States.
However, research on the biomechanics of football-related head
impacts traditionally has concentrated on the collegiate level
rather than on the high school level.
With such a large number of players in the sport, it is critical to
understand the risk associated with different levels of impact and
accurately estimate cumulative concussion risk over the course of a
practice, game, season or lifetime, Stitzel said.
In the Wake Forest Baptist study, the researchers measured the head
impact exposure in 40 high school football players by using sensors
placed in their helmets to record linear and rotational
acceleration. A total of 16,502 impacts were collected over the
course of one football season and the data were analyzed as a group
and as individual players.
Impacts were weighted according to the associated risk from linear
acceleration and rotational acceleration alone, as well as to the
combined probability of injury associated with both. This is an
improved method of capturing the cumulative effects from each
impact because it accounts for nonlinear relationships between
impact magnitude and the associated risk of injury, Stitzel
"All hits involve both linear and rotational acceleration, but
rotation coveys the idea that your head is pivoting about the neck
whereas linear acceleration is experienced from a direct blow in
more of a straight line through the center of mass of the head,"
The median impact for each player ranged from 15.2 to 27.0 g, with
an average value of 21.7 g, which shows the wide variability in the
force of impacts.
The study found that impact frequency was greater during games
(15.5) than during practices (9.4). However, overall exposure over
the course of the season was greater during practices.
This information may help teams reduce exposure to head impacts
during practices by teaching proper tackling techniques that could
reduce exposure to impacts that may result in a higher concussion
rate, the researchers reported.
Additionally, the study found a wide variation in player exposure
within the team, with a 22-fold variation in the exposure per
impact for practices and a 47-fold variation in the exposure for
impact for games.
Studies like this are vital to understanding the biomechanical
basis of head injuries related to football, Stitzel said. The
metric fully captures a player's exposure over the course of the
season and will be used in conjunction with other pre- and
post-season evaluations, including MRI and neurological tests
conducted as part of this study.
The research team hopes that this work may ultimately improve
helmet safety and design to make football a safer sport.
The study was funded by the Childress Institute for Pediatric Trauma.
Co-authors are Jillian Urban, M.S., Elizabeth Davenport, B.S., Adam
Golman, M.S., Joseph Maldjian, M.D., Christopher Whitlow, M.D., and
Alexander Powers, M.D., of Wake Forest Baptist.
Media Relations Contact: Marguerite Beck: firstname.lastname@example.org, 336-716-2415