Does disallowing body checking in non-elite 13- to 14-year-old ice hockey leagues reduce rates of injury and concussion? A cohort study in two Canadian provinces - Emery, C.; Palacios-Derflingher, L.; Black, A. M.; Eliason, P.; Krolikowski, M.; Spencer, N.; Kozak, S.; Schneider, K. J.; Babul, S.; Mrazik, M.; Lebrun, C. M.; Goulet, C.; et al. (British Journal of Sports Medicine, 2020)