It depends on how you arrange a cycle.
I used to use it the longest: the first day, chest+three heads. The next day, back to+two heads. On the third day, shoulder+forearm. The fourth day, legs. Jogging yoga on the fifth day, practicing physical strength, increasing coordination and joint strength.
Of course, if you are more professional, you will practice your upper back, lower back, thighs and calves respectively.
If you don't have much time, you want to practice all the parts at once, that is, the chest, shoulders and back alternate training compound group with two heads and three heads.
Chest muscles, back and shoulders are all large muscle groups, so you must practice in front of your arms.
When practicing chest, the back plays a supporting role. If you practice your back first, such actions as bench press and dumbbell chest push can't be aggravated, and your chest muscles can't be well exercised, so put your back behind your chest to practice.
Chest movements will definitely bring shoulder movements, so the shoulders are already very tired. Putting them behind chest exercises can immediately achieve a good effect of congestion exercises. So the order is chest-shoulder-back-two heads and three heads.
The combination of two heads and three heads can make the arm well congested and quickly thicken.