Instead of: Pilates Leg Extensions Try: Swiss-Ball Leg Lifts
Pilates is great for sculpting strong, flat abs, and this move boosts your burn even more with the added resistance of a Swiss ball. Shorter movements with your legs closer to the ground are sure to have your abs shaking within a few reps.
To do it: Lie faceup on the floor with your legs straight, holding a Swiss ball between your ankles. Raise your head and shoulders off the floor and reach both arms by your sides, hovering above the floor, palms down. Draw your abs in tight and squeeze your ankles into the ball, lifting it up until your legs are at a 45-degree angle. Slowly lower your legs until the ball gently taps the floor. That's one rep. Do 3 sets of 15 reps.