Covariates
| Category | Covariates | Levels* |
|---|---|---|
| Demographic/biometric | Age | ≤16.9 vs >16.9 years |
| Weight | ≤77 vs >77 kg | |
| Height | ≤1.78 vs >1.78 m | |
| Playing position | Backs vs forwards | |
| Injury history | Any previous injury | y/n |
| Previous concussion | y/n | |
| Use of protective equipment | Mouthguard | y/n |
| Shoulder pads | y/n | |
| Head guard | y/n | |
| Strength profile | Regular weight training | |
| Upper body strength (bench press 1RM) | ≤75 vs >75 kg | |
| Lower body strength (squat 1RM) | ≤110 vs >110 kg | |
| Level of experience/quality | Age first started playing rugby | ≤10 vs >10 years |
| School team ranking | Top vs middle vs bottom tier | |
| Involved in provincial rugby | y/n |
*Level based on median splits.
1RM, 1 repetition maximum; y/n=yes/no.