I'm on the last phase of P90X.  One of the things that they recommend is to write down how many reps, and how much weight you use for each exercise.  Yesterday, with Chest and Back, it was a pull-up and push-up fest.  When I started, all my push-ups were on my knees.  Looking back at my chart that I log my work-outs on, I could only do a few push-ups on my knees.  Today I was curious at how many push-ups I did...127 on my toes!!  127 plus 66 on my knees!  These were all kinds of push-ups:  standard, decline, military, wide fly, "diamond" and the killer "dive bomber".  Yay!!  Today I was bummed that the scale just hasn't moved as much as I would like, but looking at that accomplishment, I know I'm on the right track to building muscle.  "Just keep swimming, just keep swimming..."