USMC all the way. The best way to do sit-ups is do more. Try it this way set a clock for 2 minutes. Do as many as you can. Then drop it to 1 minute, then 30 seconds, then 15 seconds. Each time trying to pass at least half of your situps. example 100 situps in 2 minutes, goal is 50 or more in 1 mintue and so on down the line. i can do 145 in 2 minutes. It works. Try doing that 2-3 times a week and that will be all you need. The first 2 weeks though your abs will be soo sore so if you don't meet the goal don't be discouraged.