UPDATED

Brain trauma among football players (and athletes in other sports such as soccer and ice hockey) may be less the result of violent collisions that cause concussions as the cumulative effect of repetitive head impacts (RHI). The discovery has lead to increased calls by experts to take steps at all levels of sports, from professional down to the youth level, to limit exposure to such repetitive trauma, while a shrinking minority (including the NCAA) continue to urge a more cautious approach until more is known.