RECENT YEARS have seen a steady drip of troubling studies on head injuries among young players of rugby and American football. Research on schoolboy rugby published in Sports Medicine in 2023, for example, calculated that nearly two concussions result from every 1,000 tackles. As for American football, one in 20 youth players suffers a concussion over the course of a season, per a study in the Journal of Pediatrics. The real risks could be even higher, as many concussions go unreported.