For as long as i can remember i have trained bi's and back on the same day. Usually 15 sets (5 exercises) on back, 9 sets (3 exercises) on bi's. Lately i've found myself wondering should i just work on back one day, and do bi's and tri's on a diff day. My bi workout does suffer a little after a big back workout, this has been apparent lately, so before i change it up, i thought i'd see what you guys think.