If you go to practice twice a week and do pretty much the same drills and scrimmage, then a game once a week - your muscles get used to that routine. It's the same thing as when you oh, lets say, go boogie boarding in a tropical warm ocean (can you sense that I live in a cold climate?) you're sore the next day in all sorts of new places because you hadn't used those muscles in awhile. Weights are a lot of fun which can take your play to the next level.
Here's some inspiration from a lady who works hard in the gym: USA's own Alex Morgan.