Some tackling drills pose higher injury risks, study says
Researchers from the Department of Biomedical Engineering and Mechanics at Virginia Tech used biomechanical sensors to investigate exposure to head impacts in 9- to 11-year-olds engaged in a youth football program. The findings are reported in the Journal of Neurosurgery: Pediatrics.
The authors focused on two teams comprising a total of 34 players. Inside each youth's football helmet was an accelerometer array that recorded all head accelerations associated with head impacts and sent this information to a nearby computer. Videos of practice sessions and games were used to verify these head impacts.
The object of the study was to identify specific football drills that result in high-magnitude head impacts (measured as head accelerations greater than 40g).
Data was collected throughout an entire youth football season consisting of 55 practice sessions and 10 games. In 408 instances, the authors identified head acceleration measuring 40g or higher, indicating a high-magnitude impact. A total of 118 head impacts exceeded 60g acceleration and 59 impacts exceeded 70g.
Seventy percent (314) of these high-magnitude head impacts occurred during practice sessions -- a finding unlike that seen in older football players, for whom high-magnitude impacts are more often sustained during games.
Nine types of practice drills were identified: four tackling drills and five skill drills. The authors found a greater number of high-magnitude head impacts associated with tackling drills than with skill drills, even though tackling drills were conducted only half as often as offensive or defensive skill drills. The authors also identified a higher proportion of impacts greater than 60g in tackling drills (40%-50%) than in games (25%).
King of the Circle, a tackling drill in which a player holding the ball must rush from the middle of the circle through players guarding the circle perimeter, had the greatest rate of impacts -- far higher than those of other tackling drills or games.
Although only 22% of practice sessions were spent on tackling or blocking drills, the data showed that these drills led to 86% of all high-magnitude head impacts sustained during practice. Based on their findings, the authors suggest that a 10-minute reduction of time spent on tackling and blocking drills during each practice session could reduce the number of high-magnitude head impacts by 38%.
Since the very high impact rate of King of the Circle is not representative of that found in game play, the authors suggest that this drill be entirely eliminated from practice sessions.
Armed with the knowledge of which drills are more likely associated with severe head impacts as well as which drills produce greater numbers of head impacts per hour, the authors believe that coaches and league organizers can develop a practice structure that will reduce exposure to high-magnitude head impacts.
"Ultimately, the number of concussions players sustain is related to the severity and number of head impacts that they experience,” said Dr. Steven Rowson. “This study provides the first data describing activity-specific head impacts in youth football practices and identifies high-risk drills.”
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