What exercises not to do on the same day

[Simplex]

My buddy does his bi's and tri's on the same day, and I told him that its bad, but I dont know why. I just hear from everyone that it is. He hears differently, and says "Meh, its just opinion. Ive had it justified for my way, and yours".

So should one split these exercises or not?

Is mixing seated row with benching as a superset a good idea? Ive been told it helps make gains on the chest.

Is doing light dumbbell presses after my bench press a good idea? It burns like MAD but seems...excessive?

[McCarley]

So, if I understand you correctly - you offered your friend some advice without knowing what your talking about? That's not a good idea.

It depends on what you're working towards - goals.

[RipStone]

There are many different body part split combinations. The key is finding one that you like and that your body responds to. I wouldn't worry as much about what muscle groups to work together on any given day. But you should worry about if you train certain muscle groups one day, you need to wait a few days until your train others. For example, if you do chest on Monday, it would not be a good idea to train triceps or shoulders for the next 2 days. When you train your chest your are also hitting your shoulders and triceps pretty hard, so you want to let them recover before you hit them again.

[I. Kay]

What exercises you do on what days depends on your goals, recovery time in between workouts and the type of exercises you do. Spending a whole day doing nothing but curl variations and skull crushers probably isn't valuable to the average lifter. Of course, there are programs (like Great Guns) that basically do just that. But those are specialization routines that shouldn't be used year-round.

Now when you say "does" his bis and tris, do you mean just isolation exercises? Because while most guys wouldn't recommend that , there are other ways to work your bis and tris on the same day with more effectiveness. For example, you mentioned rows and bench on the same day. Lots of people do this. It's great: These are two of the most valuable compound exercises. Of course, you're working both your bis and tris pretty hard at the same time.

In other words, saying that working your bis and tris on the same day is "bad" is not true.

Now if your buddy is a smaller guy looking to gain mass, or even a bigger guy looking for strength, you could tell him that very often isolation movements aren't the optimal way to go. Replace those curls with chinups and the rope pulldowns with dips, and he'll be benefitting more all around.

Just be careful of saying that any way of working out is "bad", unless it's obvious overtraining, bad form or if your buddy has been doing the same routine for a year with no significant improvements.