I just recently joined my school's flag football team just to have a recreational activity in college. I stretch before playing but when I run a post route and pivot, I get a pain in the muscles on top of my thighs. The pain continues for the rest of the day and it feels sore. The next day i can walk fine again but they're still sore until the end of the week. By next game time I'm fine until I do that route again. Is it cause my legs are out of shape? Or am I doing something wrong?