Three choices at contact. One is 14× the others.
Dartmouth's research group coded 3,701 Ivy League game tackles by how high the tackler hit, which direction he hit from, and where his head was. Build any tackle and see it in 3D, with the odds of head contact the study found for that kind of tackle.
Odds of head contact with the neck flexed — head down, chin to chest — at contact
The highest cell in the study: medium height, from the side, neck flexed
Neck neutral, head in line with the spine. Same hit, a fraction of the odds
Pick the height, the direction and the neck.
Drag the model to turn it. Every combination is posed in 3D; the panel shows what the study found for that cell, or for its parts when the paper did not report the cell on its own.
Every reported cell, ranked.
Click a cell to build it in the 3D model. Highlighted rows are what your current tackle is made of.
The concussion studies point the same way.
The Ivy League study measured head contact. These studies measured concussions and head-injury assessments directly, in the NFL and in rugby.
Leading with the helmet
Odds ratio for tackler concussion when the helmet led into contact, NFL tacklers.
Sherwood et al. 2025 · 51 concussions vs 96 controlsHelmet as the loading point
Odds ratio when the helmet, not the shoulder, took the primary load.
Sherwood et al. 2025 · NFLHead in front of the ball carrier
Tackler concussions per 1,000 front-on tackles, head in front vs head behind.
Kawasaki et al. 2023 · 14,809 rugby tacklesUpright tackler
Head-injury assessment rate for an upright tackler vs one bent at the waist.
Tucker et al. 2017 · professional rugbyTechnique changes the count, not just the concussions.
Most head contact never becomes a concussion, and that is the point: high school players take hundreds of recorded hits a season, and the research ties brain changes to the total.
Recorded head impacts a season
For a high school lineman, the most of any position. The average player took about 650.
Broglio et al. 2011 · helmet sensors, 4 seasonsThe typical hit
Median impact per player averaged about 22g. Sensors ignore anything under a 10–20g recording floor.
Urban et al. 2013 · high schoolFewer head impacts
High school players who stuck with a tackling and blocking technique programme took fewer head impacts.
Swartz et al. 2024 · 496 Hawaii players