Hello, I'm a fitness instructor. In this case, I should practice muscles in other positions, such as chest, back, shoulders, two heads, three heads and legs. I should practice a project every day and take a day off every week. There are two possibilities. One is that your muscle quality is not good, so your muscle reaction is slow, and some people begin to feel pain on the third day. The other is that the amount of exercise is not in place, so you should increase it appropriately. Wish you success!