In brief: Professional soccer players may head the ball an average of five times a game, which adds up to 5,250 impacts to the head in a 15-year career. The impact to the head may be as high as 200 kp. Players complain of headache, pain in the neck, dizziness, irritability, insomnia, hearing disturbances, weakened memory, and abnormal alcohol reactions. Since these symptoms are subjective, additional studies are needed to understand the possible negative effects of heading the ball. Players should try to decrease the number of headings, especially on balls kicked from a short distance, and they should use proper heading techniques and light soccer balls.