This core strengthening sequence from Biggest Loser trainer Jen Widerstrom goes way beyond the standard crunch. It's two exercises that are meant to be done together. The first move targets your upper abdomen and the second works your lower abs and builds strength in your pelvic floor.
Here's how to do it: Lie on back with legs and arms straight up, and feet flexed. Crunch up and open legs into a V. With arms outstretched, reach hands between legs. Do 10 reps. Return to start; place hands behind head with legs in a V. Crunch up and bring legs together. Repeat 10 times. Do entire series 3 times.
Trainer tip: if you don't yet have the strength to keep your straight legs up during the sequence, you can do both moves with your knees bent at 90 degrees.