Frog Jumps and Mountain Climbers for Abs Exercise

Besides the usual sit ups and leg raises, I use frog jumps. I do not bunny hop, but squat down and jump forward landing solidly and then repeat for at least 50 yards. The stomach workout is intense. If possible I race a workout partner in the exercise just to make it more fun and a harder workout. I like the cardio part of the workout as much as the burn it puts on the stomach muscles.

Also, I like mountain climbers as a good stomach workout. Done quickly, it adds a nice cardio workout as well as working the stomach. Both of these exercises work other muscle groups as well.