I am worried about the CFA. I can max out the pull-ups and crunches and max the run time, but my push-ups die at about 1 1/2 minutes at 60. I'm trying to get to 75, but I just die out so quickly with the series of exercises. Haven't tried the shuttle run or basketball throw yet, though we shuttle run almost everyday in wrestling practice. What is the best way to improve my push-up stamina? Speed or numbers?