BROWN U. (US) — College football quarterbacks and running backs take the hardest hits on the field, but linemen and linebackers are hit more often, according to data from sensor-equipped helmets.
Researchers gathered data on the frequency, direction, and magnitude of head impacts from players wearing the helmets during three seasons at Brown University, Dartmouth College, and Virginia Tech.
“This allows us to quantify what the exposure is,” says Joseph Crisco, professor of orthopaedics at Brown. “It is the exposure that we need to build upon, so that we can then start understanding what the relationships are with acute and chronic head injury.”
The study, published online in the Journal of Biomechanics, documented 286,636 head blows among 314 players in the 2007-09 seasons. The data on the magnitude, frequency, and location of head blows amounts to a measure of each player’s head impact exposure and could help doctors understand the biomechanics of how blows to the head result in injury.
Concussions and other head injuries have become a source of elevated concern in football and other sports in recent years, with various leagues revising policies to protect players better. In part based on seeing this new data, league officials announced earlier this year that full-contact practices would be limited to two a week.
Hits by position
The new study documents the nature of head blows by player position. Players on the three teams wore helmets equipped with wireless sensors that measured acceleration in various directions, allowing researchers to discern how hard the hit was, how often each player was hit, and where on the helmet they were hit.
The data on head acceleration and hit direction are used to calculate a composite score of exposure called HITsp that might be a good predictor of concussion. On average, running backs had the highest HITsp, 36.1, followed by quarterbacks with 34.5 and linebackers at 32.6.
Offensive and defensive linemen had the lowest HITsp numbers, with 29.0 and 28.9 respectively, but along with linebackers, were hit on the head most often. Doctors worry not only about hit severity, but also hit frequency, because repeated head impacts may cause “subconcussive” neurological damage over time.
Analyzing head impacts by position can help football league officials and equipment designers begin to think about ways to make players safer.
“It will allow us to begin to understand how to control the exposures,” Crisco says. Controlling head impact exposure is critical, he adds, because there are currently no treatments for acute or chronic brain injuries, and helmets cannot prevent injuries for all players in all situations. Possibilities include rule changes and designing helmets for specific positions.
Crisco and colleagues are now analyzing data about concussions during the three seasons to determine how and whether head impact exposure is associated with injury. He recently co-authored another paper about male and female collegiate hockey players, which reported that although women were diagnosed with more concussions, they sustained fewer and less severe head impacts.
Crisco and Dartmouth engineer Richard Greenwald wrote a commentary published in Current Sports Medicine Reports arguing that intentional use of the head in sports should be curbed.
“We propose the adoption of rules—or in some sports, we champion the enforcement of existing rules—that eliminate intentional head contact in helmeted sports. When coupled with education that leads to modified tackling, blocking, or checking techniques, these rules will reduce head impact exposure and have the potential to reduce the incidence and severity of brain injury.”
The study was funded by the National Institute of Child Health and Human Development and the National Operating Committee on Standards for Athletic Equipment.
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