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216 Who’s keeping score? The effect of a score differential based running time rule on head impact rates in Canadian high school tackle football
  1. M Patrick Pankow1,3,9,
  2. Reid A Syrydiuk1,3,9,
  3. Ash T Kolstad1,3,9,
  4. Sagar Grewal1,
  5. Christian A Clermont1,3,
  6. Christopher R Dennison8,
  7. Brent E Hagel1,3,6,7,9,
  8. Martin Mrazik2,
  9. Carolyn A Emery1,3,4,5,6,7,9
  1. 1Sport Injury Prevention Research Centre, Faculty of Kinesiology – University of Calgary, Calgary, Canada
  2. 2Faculty of Education – University of Alberta, Edmonton, Canada
  3. 3Alberta Children’s Hospital Research Institute, Calgary, Canada
  4. 4Hotchkiss Brain Institute – University of Calgary, Calgary, Canada
  5. 5Evidence Sport and Spinal Therapy, Calgary, Canada
  6. 6Departments of Paediatrics and Community Health Sciences, Cumming School of Medicine – University of Calgary, Calgary, Canada
  7. 7O’Brien Institute for Public Health, Cumming School of Medicine – University of Calgary, Calgary, Canada
  8. 8Department of Mechanical Engineering – University of Victoria, Victoria, Canada
  9. 9Integrated Concussion Research Program – University of Calgary, Calgary, Canada


Background Due to postulated associated long-term health issues in athletes, concussions and head impacts are of concern in tackle football. Football Canada mandated a game clock running-time rule (RTR) in the event of a second-half 35-point difference in games, citing player safety as the main rationale.

Objective To examine the effectiveness of RTR on reducing game-related head impact rates in Canadian high school football using video analysis.

Design Cross-sectional.

Setting Calgary, Canada.

Participants Players on two junior division high school teams (ages 15–16) in Calgary, Alberta were included. Fourteen games from the 2019 season (Team A: n=8, Team B: n=6) were videotaped for analyses.

Assessment of Risk Factors Traditionally, the clock stops between plays until the referee signals for the clock to resume. With RTR the clock continues (except during exceptional circumstances such as injury, scores, or timeouts) in the event of a point differential of 35 points or greater in the second half of a game.

Main Outcome Measurements Head impacts were reported as incidence rates (IR) [# head impacts/100 player-game-minutes (PGM) (95% confidence intervals (95% CI)]. Incidence rate ratios (IRR), offset for PGM, adjusted for game outcome (e.g., win, loss) and clustering by team game were used to compare score differential in games with and without running-time (≥35 points vs. <35 points) by team unit (e.g., offense, defense).

Results RTR games yielded 24% fewer plays than non-RTR games (IRR: 0.76, 95% CI: 0.68, 0.84). Head impact IR in RTR games were lower than non-RTR games for offensive units (IRR:0.80; 95% CI:0.68, 0.95) and defensive units (IRR:0.76; 95% CI:0.59, 0.99). There were no differences in special teams units.

Conclusions RTR reduced game-related head impact IRs in this cohort for both offensive and defensive units. Sport governing bodies should consider the potential effect of RTR on injury and concussion rates at the youth level.

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