My daughter cheered through college. Injury wise, its pretty much like football. Not a question of if you will get injured but, how bad will it be. Even with mats when a person falls from more than 5 feet somethng is going to get hurt.
In high school, they started practice before the football team and were still going after the team returned.
Technically not a sport. But, they practice and cheer for 11 months out of the year.