It's not that the intensity is not enough, but that practicing equals not practicing. If it is a big muscle such as the pectoral muscle and quadriceps, it will hurt for at least three days after training.

Even this biceps, unless you have two or three years' experience, the pain of 1~2 days is normal.

The first thing you should do is to increase the weight and then resist fatigue. Add a group to ensure that one movement can exhaust at least three times, and one part (such as biceps) can exhaust at least 10 times, so that the movement is basically in place. ...