People who don't exercise for a long time will feel this way if they don't go to the gym for a week or two. Just after practice, the muscles will be congested and swollen. And there is a feeling of muscle swelling, which gradually decreases and lasts for several days. After a week, it's time to enter a new exercise cycle. If the muscles are not properly stimulated, the muscles will naturally feel "declining". This shows that the muscle quality is not enough. People who exercise for a long time will be better, their muscles will be stimulated effectively and regularly, and they will have enough growth time.