I do chest and bi's and my tri's w/ my shoulders. Here is my reasoning behind it. When I do chest, I use at least 2 pushing movements ie bench press or incline. Therefore my tri's are rather fatigued by the time it comes to train them, thus causing a submaximal workout. When I do shoulders, I normally do only one pressing movement, thus putting less stress on my tri's and giving me a better workout. I have seen good results w/ this program, my closegrip bench went from 245 for 6 to 275 for 6 within a month of switching to this split.