 And so this question of how many sit-ups should I be doing versus how many am I doing? But basically, the article goes on to say that 40 sit-ups is a good number. Now, it may not chisel you out a six-pack only doing 40 a day, but it'll keep your core strong. And I think that's important. Now, how do you do sit-ups? Are you doing curls? Are you going all the way up? Are you doing leg swings? Are you throwing medicine balls around?