There is no such thing as 'just an ankle sprain'. If not rehabilitated correctly, an ankle sprain increases the chances of an ACL tear. Proper rehabilitation is easy and short when compared to an ACL.
A quick search will provide thousands of links on 'football helmets and concussions.' They range from the scientific to the alarmist blogger. The facts are here for you to make an informed decision.
Here are some helpful tips and tricks I used to pass the Athletic Training Certification exam. Many of these are applicable to other certification exams and test taking in general.