It's the number that I feel comfortable doing in a set without tiring myself out. I think a short while back when my son asked how many push ups I can do in a row, and I tried it, the number was in the low 70s. I think I will start doing maxi Sundays, beginning this week. Going to do the max number of reps every Sunday to see if I improved and how much I improved from doing this 100 till 100k challenge.