Man, you are going to get a ton of answers on this one. Chest and triceps, back and biceps, chest and biceps, back and triceps, shoulders and triceps, shoulders and biceps, push/pull/legs and the list goes on. There does seem to be one unwritten rule though...train legs by themselves. I guess in the end it all depends on what works for you and gets you to grow!
many choices here...i can tell you what i do
1-Back : with it i do sometimes biceps and sometimes rear deltoids and sometimes both
2- Chest: Alone or with it sometimes triceps , sometimes shoulders without rear, sometimes both
3- legs: mostly alone
4- abs: 3-4 times a week i do them with anything
and of course sometimes i do just one muscle a day but i never do chest the day after triceps or shoulders, or back the day after biceps.
There are very few absolutes in this field though, many guys find success in many different routines.
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