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11.28 Who’s keeping score? The effect of a mercy rule on head impact rates in Canadian high-school tackle football games
  1. M Patrick Pankow1,2,3,4,
  2. Reid Syrydiuk1,2,3,
  3. Ash T Kolstad1,2,3,4,
  4. Christopher R Dennison5,6,
  5. Martin Mrazik7,
  6. Brent E Hagel1,2,3,8,9,
  7. Carolyn A Emery1,2,3,4,8,9
  1. 1Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Canada
  2. 2O’Brien Institute of Public Health, University of Calgary, Calgary, Canada
  3. 3Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Canada
  4. 4Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
  5. 5Department of Mechanical Engineering, University of Victoria, Victoria, Canada
  6. 6Biomedical Instrumentation Lab, Department of Mechanical Engineering, University of Alberta, Edmonton, Canada
  7. 7Department of Educational Psychology, University of Alberta, Edmonton, Canada
  8. 8Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Canada
  9. 9Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Canada

Abstract

Objective To examine the association between the Mercy Rule (MR) and head impact incidence rates (IR) in Canadian high school football games.

Design Cross-sectional video-analysis study.

Setting Football fields (Calgary, Canada).

Participants In 2019, two high-school football teams (ages 15–16) in Calgary, Canada had a total of 16 team-games (N=8 games) videorecorded and analyzed using Dartfish software.

Interventions (or Assessment of Risk Factors) As per Football Canada’s Tackle Football Rulebook, the MR (initiates continuous running time) comes into effect when the score differential becomes 35 points or more in the second half of the game.

Outcome Measures The outcome measure was head impacts. A negative binomial regression adjusted for cluster by team-game was used to estimate head impact IRs (/team-game and/team-2nd-half) for games with and without the MR in effect. The corresponding incidence rate ratios (IRR) were also estimated.

Main Results Games with the MR in effect had 28% fewer plays (39% fewer in the 2nd-half) and 27% fewer head impacts per team-game [IR=241.67 (95%CI:199.24, 293.13)] compared with games without [IR=328.91 (95%CI:313.04, 345.57); IRR=0.73 (95% CI:0.61, 0.89)]. In the 2nd-half of games with the MR in effect there were 40% fewer head impacts per team-2nd-half [IR2nd-half=99.16 (95%CI:76.81, 128.03)] compared with games without [IR2nd-half=166.20 (95%CI:156.75, 176.22); IRR2nd-half=0.60 (95%CI:0.47, 0.76].

Conclusions In this novel evaluation of the Mercy Rule, running time was associated with a 27% lower head impact IR in games (40% in 2nd-half). Consideration for future research should include examining the effect of the MR on concussion IRs.

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