I use pyramids at the beginning of my class. Have the class do 2 pushups followed by 2 crunches. They will then complete 4 pushups and 4 crunches, followed by a series of 6, 8, and 10 pushups and crunches. Then have them work down the opposite side of the pyramid by doing 8, 6, 4, and 2. You can also go by single counts but going by 2's helps to break the monotony. It goes well at the beginning of a bootcamp class. Gotta love that good ole army training. Beat Navy.