played a role 446,000 sports-related head injuries 446,000 sports-related head injuries One study played a role American Association of Neurological Surgeons safest sports 446,000 sports-related head injuries American Association of Neurological Surgeons almost twice as many cyclists as football players 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries played a role force of a professional boxer's fist 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries sports with the highest number of reported head injuries sports-related head injury 446,000 sports-related head injuries American Association of Neurological Surgeons 446,000 sports-related head injuries played a role 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries played a role 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries played a role 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries American Association of Neurological Surgeons 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries American Association of Neurological Surgeons 446,000 sports-related head injuries 446,000 sports-related head injuries American Association of Neurological Surgeons played a role played a role 446,000 sports-related head injuries American Association of Neurological Surgeons 446,000 sports-related head injuries recent study 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries 446,000 sports-related head injuries