I took some of your advice yesterday, when doing Chest. I did my usual routine, going up to 60lb. Then I added another set of 12 with the 55. And actually, that felt really good. Im still not able to push over 60 yet . . but the extra set gave me that burn out that I had been looking for. I am sore today - and I like that.
My Trainer said he added the KG ball for the end of the Chest routine to slowly work the lower pecs. He went on about how important it is to work the upper pecs and less on the lower because the lower pecs grow much faster . . . if that makes sense??