400 Section - Man-Down: Investigating the Effect of an On-Field Player Count Reduction on Head Impacts, Suspected Concussion and Non-Concussion Injuries

Tuesday, May 19, 2026

6:00 PM - 7:30 PM PT

Presenting Author/Autor expositor(s)

MP

Mark P. Pankow, MD, MSc

Resident Physician
University of Alberta
Edmonton, Alberta, Canada

Co-Author/Coautor(s)

RS

Reid Syrydiuk, MSc

Doctural Student
Michigan Concussion Center, University of Michigan
Ann Arbor, Michigan, United States
JC

Joshua Cairns, MSc

Graduate Student
Sport Injury Prevention Research Centre, University of Calgary
Calgary, Alberta, Canada
AK

Ashley T. Kolstad, MSc

Doctural Candidate
Sport Injury Prevention Research Centre, University of Calgary
Calgary, Alberta, Canada
SB

Steven P. Broglio, PhD, ATC

Professor of Kinesiology, Adjunct Professor of Neurology and of Physical Medicine and Rehabilitation
Michigan Concussion Center, University of Michigan
Ann Arbor, Michigan, United States
MM

Martin Mrazik, MEd, PhD, R.Psych

Professor, Faculty of Education - Educational Psychology Dept
University of Alberta
Edmonton, Alberta, Canada
CE

Carolyn A. Emery, PhD, PT

Professor of Kinesiology
Sport Injury Prevention Research Centre, University of Calgary
Calgary, Alberta, Canada

Objectives : Tackle football has head impact (HI), concussion and non-concussion injury rates amongst the highest of popular North American youth sports. The purpose of this study was to investigate the effect of a reduction in the on-field-player-count (OFPC) on HI, suspected concussion (SC), and suspected non-concussion injury (SNCI) rates amongst 12-15-year-old football players in Calgary, Canada.

Design:

This was a cross-sectional study. Due to COVID-19 restrictions, the OFPC (9-players-per-team) and field-size (150x50 yards) were reduced in 2020. The 2021 season (12v12) returned to 12-players-per-team and a 150x65-yard field. Twenty regular-season team-games per season were video-recorded and analyzed. SC were identified using previously published criteria (Davis et al., 2019 & Davis et al., 2019). SNCI were coded if a player received medical attention but did not display the aforementioned SC criteria. HI, SC, and SNCI incidence rates (IR) and incidence rate ratios (IRR) per 100-player-plays were calculated overall, and when restricted to only Offensive/Defensive plays [O/D] and Special Teams plays [ST], respectively.

Results: A total of 4253 HI, 12 SC, and 40 SNCI were coded from 3982 plays over the 2 seasons. The 9v9, and 12v12 player-field-density (PFD) was 2.40 and 2.46-players-per-1000-yards² respectively. Compared with the 12v12 season, HI rates in the 9v9 season were higher Overall (IRR:1.19, 95%CI:1.12, 1.25), for O/D plays (IRR:1.17, 95%CI:1.10, 1.25), and ST plays (IRR:1.33, 95%CI:1.15, 1.54). There was no significant difference in the Overall, O/D only or ST only rates of SC or SNCI.

Conclusion: These results suggest that reducing OFPC (while maintaining PFD) may be an ineffective, or even a counterproductive (for HI), intervention to improve the safety of youth football in Canada. As the safety of youth athletes is of utmost priority, ongoing research is critical to better understand the epidemiology of injuries/HI as well as to develop, evaluate, and subsequently implement effective preventative interventions.