Ask the great gods, go to the gym for more than an hour, and when you come back, you are weak. Is this an effect? But why did I lose my muscles the next day?

This is normal! Because at first, your body muscles haven't adapted to your exercise, so you will feel weak all over. The next day, wait for the muscles to rest, and then start slowly. You just feel tight, not as tired as the first day! Keep moving! Maybe there will be a sense of muscle in the future, but that is normal! This is an adaptive buffering process of muscles!