becouse of an injury in my bicep muscle and tricedp muscle,i was training biceps on back days after back and tricep on chest days after chest,this is one of the ways of setting a training program,pull muscles together,back and bi's and push muscles together chest and tri's,but i had a personal reason to train that way and that is becouse of my injuries, the back workout will work as a good warm up for my biceps it will fatigue them and that will cause me to use less poundage in my bicep workout and less sets as well,the same goes for my chest and tricep.now that i am healed i do biceps after chest and triceps after back,this switch have helped me up the poundege quite a bit in my arm workouts.