Football players are very susceptible to concussions. A concussion is a change in mental state due to a traumatic impact. Not all those who suffer a concussion will lose consciousness. Some signs that a concussion has been sustained are headache, dizziness, nausea, loss of balance, drowsiness, numbness/tingling, difficulty concentrating, and blurry vision. The athlete should return to play only when clearance is granted by a health care professional.