Estimation of head
impact exposure in high school football

SP, Martini D, Kasper L, Eckner JT, Kutcher JS. Am J Sports Med. Ahead of

Take Home Message: Limiting
or eliminating contact football practices may reduce the number of head impacts
sustained by athletes by 18 to 39% over the course of a season.

impacts, those not resulting in a concussion injury, have been shown to
contribute to cognitive impairment. On average a high school football athlete
receives 50 head impacts a week, which may lead to future cognitive impairment.
It may be desirable to reduce the number of impacts by changing rules related
to practices and games but it is unclear if this will be sufficient since we
don’t know how many impacts occur during contact and noncontact practices.
Therefore, Broglio et al compared the number and magnitude of head impacts
resulting from games, contact practices, and non-contact practices to estimate
the effect of limiting contact practices on head impact exposure in high school
football. The authors utilized the HIT System to measure head impacts and followed
42 high-school athletes (18 lineman; 2 quarterbacks; 13 wide receivers, center
backs, and safeties; and 9 tight ends running backs, linebackers) over 6
seasons. On average athletes received 774 head impacts per season. Linemen
sustained the highest number of impacts per athlete (~1076 impacts); followed
by tight ends, running backs, and linebackers (~779 impacts); wide receivers,
center backs, and safeties (~417 impacts); and quarterbacks (~356 impacts). A
typical athlete sustained about 2 head impacts per non-contact practice, ~11
head impacts per contact practice, and ~24 head impacts per game. The magnitudes
of linear acceleration of the head impacts
were also higher in games (~26.9g) compared to both contact (~25.2g) and
non-contact practices (25.7g). There were no differences in the magnitude of
linear acceleration between positions. However, the tight end, running backs,
and linebackers received higher magnitudes of rotational acceleration
compared to the other player groups. Head impacts suffered during a game had
the highest magnitude of rotational acceleration (~1769.1rad/s/s) compared to contact
(~1645.8rad/s/s) and non-contact practices (~1570.1rad/s/s). The authors
estimated that limiting a team to 1 contact practice per week would reduce head
impacts 18% (138 less head impacts per season). Eliminating all contact
practices would reduce head impacts by 39% (301 less head impacts per season) across
all players.

number and magnitude of head impacts reported in this study were similar to
previous past studies. This demonstrated that the frequency and magnitude of
head impacts have been alarmingly high, and could benefit from a rule change. A
change in the amount of contact-practices would be especially beneficial for linemen,
who received the most number of head impacts. Additionally, it would support
tight ends, running backs, and linebackers who received the highest magnitude
of head impacts compared with players at other positions. However, all athletes
could benefit from less contact. It was estimated that if there were no
contact-practices that would eliminate 31 head impacts per week, where the average
number of head impacts would go from 50 to 20 head impacts per athlete per
week. However, it is not known if this decrease in head impacts would be large
enough to have a protective effect. An 18% reduction may not be large enough to
prevent long-term cognitive impairment but then again this reduction over 8
years may be beneficial to an athlete who plays high school and then college
football. Future studies will need to measure and evaluate if reducing head
impacts leads to less cognitive impairment over the course of 1 season, 1 year,
4 years, or longer. Due to the large number and magnitude of head impacts that
occur during a game focusing on safe tackling techniques (e.g., not leading
with the head) as well as reducing the number of overall head impacts may also be
necessary to decrease the number of high-load head impacts an athlete sustains.
Overall, we may need to focus on reducing the number and severity of head
impacts in games and practices but we also need to better understand how many
hits we need to prevent to have a benefit.

Questions for Discussion:
Do you think reducing the number of head impacts in football could lower the
risk of long-term cerebral dysfunction?
Do you
think having 1 or no contact practices would still get the athlete ready for a

by: Jane McDevitt PhD
by: Jeffrey Driban


Broglio SP, Martini D, Kasper L, Eckner JT, & Kutcher JS (2013). Estimation of Head Impact Exposure in High School Football: Implications for Regulating Contact Practices. The American Journal of Sports Medicine PMID: 24001576