Participant demographic information for the prospective cohort and nested case–control analytic approaches
| Variable | Prospective cohort | Nested case–control | |
| Player-seasons (n=5356) | Player concussions (cases; n=490) | Player acute MSK injuries (controls; n=420) | |
| Weight (kg), mean (SD) | 55.1 (14.7) | 57.1 (14.0) | 60.7 (14.8) |
| Missing, n (%) | 535 (10.0) | 72 (14.7) | 52 (12.4) |
| Level of play, n (%) | |||
| Under 13 | 1535 (28.7) | 84 (17.1) | 48 (11.4) |
| Under 15 | 2255 (42.1) | 235 (48.0) | 176 (41.9) |
| Under 18 | 1566 (29.2) | 171 (34.9) | 196 (46.7) |
| Missing | 0 (0) | 0 (0) | 0 (0) |
| Policy permitting body checking, n (%) | |||
| No | 2456 (45.9) | 164 (33.5) | 99 (23.6) |
| Yes | 2719 (50.8) | 310 (63.3) | 318 (75.7) |
| Missing | 181 (3.4) | 16 (3.3) | 3 (0.7) |
| Previous concussion, n (%) | |||
| No | 3020 (56.4) | 202 (41.2) | 192 (45.7) |
| Yes | 2030 (37.9) | 250 (51.0) | 199 (47.4) |
| Missing | 306 (5.7) | 38 (7.8) | 29 (6.9) |
| Position, n (%) | |||
| Forward | 2713 (50.7) | 251 (51.2) | 239 (56.9) |
| Defence | 1604 (30.0) | 163 (33.3) | 123 (29.3) |
| Goalie | 446 (8.3) | 28 (5.7) | 21 (5.0) |
| Missing | 593 (11.1) | 48 (9.8) | 37 (8.8) |
| Sex, n (%) | |||
| Male | 4803 (89.7) | 422 (86.1) | 384 (91.4) |
| Female | 530 (9.9) | 68 (13.9) | 34 (8.1) |
| Missing | 23 (0.4) | 0 (0) | 2 (0.5) |
Level of play included under 13 (formerly Pee Wee, ages 11–12), under 15 (formerly Bantam, ages 13–14) and under 18 (formerly Midget, ages 15–17).
MSK, musculoskeletal.