Your mission is to do the whole deck before next Tuesday.
The rules: You can stop whenever you want but if you turn a card over, you have to do the number of the card. So you turn a 6 of hearts? You do 6 sit ups.
Your choice if you want face cards to be 10 or j=11, etc
If you just have 5 minutes, you can do as many cards as you can in that time. Or do it during commercials. Etc.