title: Practice type effects on head impact in collegiate football.
abstract: OBJECT IVE: This study directly compares the number and severity of subconcussive head impacts sustained during helmet-only practices, shell practices, full-pad practices, and competitive games in a National Collegiate Athletic Association (NCAA) Division I-A football team. The goal of the study was to determine whether subconcussive head impact in collegiate athletes varies with practice type, which is currently unregulated by the NCAA.
  
  
  METHODS
  Over an entire season, a cohort of 20 collegiate football players wore impact-sensing mastoid patches that measured the linear and rotational acceleration of all head impacts during a total of 890 athletic exposures. Data were analyzed to compare the number of head impacts, head impact burden, and average impact severity during helmet-only, shell, and full-pad practices, and games.
  
  
  RESULTS
  Helmet-only, shell, and full-pad practices and games all significantly differed from each other (p ≤ 0.05) in the mean number of impacts for each event, with the number of impacts being greatest for games, then full-pad practices, then shell practices, and then helmet-only practices. The cumulative distributions for both linear and rotational acceleration differed between all event types (p < 0.01), with the acceleration distribution being similarly greatest for games, then full-pad practices, then shell practices, and then helmet-only practices. For both linear and rotational acceleration, helmet-only practices had a lower average impact severity when compared with other event types (p < 0.001). However, the average impact severity did not differ between any comparisons of shell and full-pad practices, and games.
  
  
  CONCLUSIONS
  Helmet-only, shell, and full-pad practices, and games result in distinct head impact profiles per event, with each succeeding event type receiving more impacts than the one before. Both the number of head impacts and cumulative impact burden during practice are categorically less than in games. In practice events, the number and cumulative burden of head impacts per event increases with the amount of equipment worn. The average severity of individual impacts is relatively consistent across event types, with the exception of helmet-only practices. The number of hits experienced during each event type is the main driver of event type differences in impact burden per athletic exposure, rather than the average severity of impacts that occur during the event. These findings suggest that regulation of practice equipment could be a fair and effective way to substantially reduce subconcussive head impact in thousands of collegiate football players.
authors.affiliation: Department of Radiology and Medical Imaging;
authors.forename: Bryson B
authors.initials: BB
authors.lastname: Reynolds
authors.affiliation: Public Health Sciences;
authors.forename: James
authors.initials: J
authors.lastname: Patrie
authors.affiliation: Department of Radiology and Medical Imaging;
authors.forename: Erich J
authors.initials: EJ
authors.lastname: Henry
authors.affiliation: Department of Neurology; and.
authors.forename: Howard P
authors.initials: HP
authors.lastname: Goodkin
authors.affiliation: Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, Virginia; and.
authors.forename: Donna K
authors.initials: DK
authors.lastname: Broshek
authors.affiliation: Department of Radiology, Stanford University, Stanford, California.
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
authors.affiliation: Department of Radiology and Medical Imaging;
authors.forename: T Jason
authors.initials: TJ
authors.lastname: Druzgal
mesh_terms: D000054:Acceleration; D001696:Biomechanical Phenomena; D015374:Biosensing Techniques; D001822:Body Burden; D001924:Brain Concussion; D001930:Brain Injuries / Q000453:epidemiology; D015331:Cohort Studies; D006259:Craniocerebral Trauma / Q000453:epidemiology*; D005538:Football / Q000293:injuries* / Q000706:statistics & numerical data; D006260:Head Protective Devices; D006801:Humans; D015601:Injury Severity Score; D053208:Kaplan-Meier Estimate; D008297:Male; D012399:Rotation; D055815:Young Adult
keywords: CTE = chronic traumatic encephalopathy; GEE = generalized estimating equation; HITS = Head Impact Telemetry System; NCAA = National Collegiate Athletic Association; PLA = peak linear acceleration; PRA = peak rotational acceleration; SRC = sports-related concussion; UVa = University of Virginia; accelerometer; athlete; biomechanics; football; subconcussion; traumatic brain injury