Researchers at the University of Virginia (UVa) examined the number and severity of subconcussive head impacts sustained by college football players over an entire season during practices and games. The researchers found that the number of head impacts varied depending on the intensity of the activity. Findings in this case are reported and discussed in "Practice type effects on head impact in collegiate football," by Bryson B. Reynolds and colleagues, published today online, ahead of print, in the Journal of Neurosurgery.
The researchers examined head impacts sustained by UVa football players during 10 helmet-only practices, 29 shell (also known as half-pad) practices, and 27 full-pad practices, as well as during 12 games. The three categories of practices are important because, as the authors state, "the level of protective equipment worn is generally a good proxy measure for the intensity of a practice." Under his helmet, each player wore an impact-sensing patch (xPatch®) over his left or right mastoid process. The patch measured the linear and rotational acceleration of each head impact. The researchers collected data on the number of impacts, the average severity of impacts, and the head impact burden for each type of practice and for games. In all, 890 instances of head impact in16 players were examined.
There were significant differences in the mean number of head impacts per event (practice session or game) for the various types of activities, with the number increasing according to the intensity of the activity. Thus games had the largest mean number of head impacts, followed by full-pad, shell, and helmet-only practices.
This pattern was also apparent when the researchers examined the cumulative distributions of both linear and rotational acceleration (that is, the impact burden). There again, games had the largest cumulative distribution of both linear and rotational acceleration, followed by full-pad, shell, and helmet-only practices.
The pattern changed with respect to average impact severity. The researchers observed no significant differences between shell practices, full-pad practices, and games. Nevertheless, helmet-only practices had a lower average impact severity than the other activities.
The researchers discuss the fact that citing a general lack of data, the National Collegiate Athletic Association (NCAA) has not established clearly defined rules concerning the intensity of practices or the number of live-contact practices during a season or postseason. Jason Druzgal, MD, PhD, corresponding author of the article, notes that, "The results of the paper are actually very intuitive, but unlike the proactive approach of the NFL, the NCAA has been waiting for data to support their evolving football guidelines and regulations. The results of our study start to provide some of that data." The authors suggest that greater regulation of football practices could reduce the burden of head impact in college football players, while advocating that more research be undertaken to identify the cause and nature of practice type differences.
Dr. Druzgal commented that this study represents the first published use of the xPatch®, manufactured by X2 Biosystems (Seattle and Silicon Valley).
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