Many barre and pilates classes challenge you to a round of 100s, to really zero in on your lower abs. Perfect your form with the help of Pure Barre's Sarah Wingo, and you'll have a tighter tummy in no time.
Here's how to do it: Curl back into a ball, chin to chest. Extend your legs 45 degrees. Zip them together, and point your toes. Place your hands alongside your body—arms straight, palms down, fingers together. Now pump your arms up and down 100 times.
Trainer tip: To achieve perfect form, press your lower back against the ground, and keep the tips of your shoulder blades off the mat. Relax your upper body, pull your naval straight down—and don't forget to breathe!