Originally Posted by Hypertrophy
Yes, your tri's or bi's will be fatigued. However, do not let your ego keep you from training them after chest or back. Here is the reason. You will have to go lighter, this does not matter. Because your tri's or bi's have been pre-exhausted, they are obviously going to be fatigued. Your muscles do not know how much weight you have on the bar, they just recruit the muscle fibers that are needed to perform the lift. Therfore, if you are still training as "heavy as possible" (even though it is lighter) you are still going to maximally recruit all your fibers. The other upside, already mentioned, less volume is required because of pre-exhaustion.