This problem should be solved in two parts. First, the number of groups, that is, the amount of training, varies from person to person. There is no best fitness plan (especially muscle training), only the one that suits you best. It depends on your training cycle (that is, once every few days), nutrition and recovery. Professional athletes have special sports nutritional supplements and professional nutritional meals, so they need a lot of training to recover their muscles. For example, if you cycle for 3-5 days, you can practice 3-5 movements for each part and 4-8 groups for each group. However, the average person's auxiliary means can't reach the professional level, and blindly increasing the amount of training will lead to poor muscle recovery and even injury. It is recommended to practice 2-3 movements of each part every 5-7 days, and 3-5 groups are appropriate for each movement. If your muscles are still sore in the next training, it means that your training volume is too large and should be reduced appropriately.