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Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine
Mar 18, 2025;

Who Is Keeping Score: The Effect of a Mercy Rule on Head Impact Rates in Canadian High School Tackle Football Games.

Mark Patrick Pankow, Reid Syrydiuk, Ash T Kolstad, Christopher R Dennison, Martin Mrazik, Brent E Hagel, Carolyn Emery
Author Information
  1. Mark Patrick Pankow: Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada. ORCID
  2. Reid Syrydiuk: Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
  3. Ash T Kolstad: Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
  4. Christopher R Dennison: Biomechanics and Instrumentation Lab, Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada.
  5. Martin Mrazik: Department of Educational Psychology, University of Alberta, Edmonton, Alberta, Canada.
  6. Brent E Hagel: Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
  7. Carolyn Emery: Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
PMID: 40099916 DOI: 10.1097/JSM.0000000000001345

Abstract

OBJECTIVE: To examine the association between the Mercy Rule (MR) and head impact incidence rates (IRs) in Canadian high school football games.
DESIGN: Cross-sectional.
SETTING: Calgary, Canada.
PARTICIPANTS: Two high school football teams (ages 15-16 years) had a total of 16 team-games videorecorded and analyzed.
INTERVENTIONS: The MR mandates continuous running time in the second half of games when the score differential is 35 points or greater.
MAIN OUTCOME MEASURES: Head impact IRs and incidence rate ratios (IRRs) were used to compare head impact rates in MR and non-MR games.
RESULTS: Mercy Rule games had 28% fewer plays, and the head impact IR per team-game was 27% lower [IRR, 0.73; 95% confidence interval (CI), 0.61-0.89] in MR games (IR, 241.67; 95% CI, 199.24, 293.13) than in non-MR games (IR, 328.91; 95% CI, 313.04, 345.57). Across all games (MR and non-MR), running plays accounted for more than half of all head impacts, and the head impact rates for running plays exceeded all other play types except for a sack of the quarterback. Players engaged in blocks (blocking or being blocked) accounted for 68.90% of all recorded head impacts. The highest proportion of impacts involved the front of the helmet (54.85%). There was no difference in head impact rates by player-play comparing MR and non-MR games (IRR, 1.01; 95% CI, 0.85, 1.19).
CONCLUSIONS: Given the concerns for potential long-term consequences of repetitive head impacts, the MR is a prevention strategy by which head impact rates can be significantly lowered when a significant score differential exists.

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Journal Article

Word Cloud

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