I feel sore the next day, which usually happens a few days before training, or when I retrain after a long pause in training. Sometimes the pain even lasts for a week, which is the performance that the muscles can't adapt to the sudden increase of heavy load training.

However, if you have been training for a period of time and trained properly, you should feel muscle pain within one to two hours after training, which is caused by lactic acid accumulation, and the pain should disappear after lactic acid is eliminated. If you still feel pain the next day, this situation is not normal. The reason may be that the interval between two training sessions is too long (for example, more than one week), or you just changed a movement, the new movement mobilized some muscles that were not used in the original movement, or suddenly increased the training intensity greatly, and so on.