Personally, I suggest that every practice must be thoroughly practiced, that is, the muscles in this part can no longer grind their teeth. In this case, you can rest for 24 hours. If your physique is different and your recovery is slow, 48 hours or even 72 hours is not a big problem, but there is a bottom line. Generally, the interval between two exercises of a certain muscle group should not exceed 120 hours, that is, five days, and should not exceed 65430 hours.
In addition, the endurance and endurance of each muscle group are different, and it is unreasonable for different muscle groups to use the same weight or spend the same time. Personally, I think the training frequency of abdominal muscles is three to four times a week. Every time the upper abdomen does sit-ups or lies flat, the upper body touches the knee, and each group has obvious pain. The lower abdomen does abdominal rolling exercise.
The pectoral muscle belongs to a large muscle group. It is best not to practice more than three times a week, but you must practice thoroughly every time, because practicing chest muscles, such as barbell bench press, will bring triceps movement. Triceps is not a big muscle group, so there is too much chest muscle training. On the one hand, the growth time of the chest muscle is not enough, and at the same time, the triceps will be very tired and the hands will feel very weak.