Lying faceup, swipe your legs together left and right in a 180-degree arc. The glitch is that women tend to recruit their legs and hip flexors to do this exercise. "When you release your grip on those wrong muscles to engage the right ones—in this case your core— you can access your full range of mobility and strength, and suddenly this movement becomes so much more accessible and effective for shaping your body," Widerstrom says. (Master it, then tackle this 10-move oblique workout to test your strength.)
1. Teach your body to move, brake, and change directions fluidly with a barbell twist. Stand with feet together, with an empty barbell (or a broomstick) racked on your back across your shoulder blades, lightly gripping the bar with an overhand grip, elbows bent downward. Keep the torso long and hips square, then rotate torso toward right until you have no further range of motion toward your right side. Switch sides; repeat. Do 2 to 3 sets of 10 to 12 reps, alternating sides.
2. Move your legs as one—but without as much weight—with bent-leg wipers. Lie faceup on floor with arms extended out to sides and knees bent over hips. Keeping legs together at 90 degrees, drop knees toward left, letting your right hip come off the floor, to hover 1 inch above floor. Lift knees to start, then lower them toward right. Do 2 to 3 sets of 10 to 12 reps, alternating sides.
3. Do single-leg wipers to learn how to control the movement in its full range. Lie faceup on floor with arms extended out to sides, right leg extended upward and bent left knee over hips. Keeping knees together, drop legs toward left to hover 1 inch above floor, letting your right hip leave the ground. Lift your legs back the way they came, then lower them toward right. Do 2 to 3 sets of 10 to 12 reps, alternating sides.
The Perfect Windshield Wiper: Lie faceup on floor with arms extended out to sides and legs extended over hips. With ribs pressing into floor and legs together, drop legs toward left as your right hip lifts off the floor, to hover 1 inch above floor. Trace your legs back to start, then lower them toward the right. "As your legs reach away from your core, your body becomes very tight in order to keep you stable and connected to the floor," Widerstrom says. "Then when your legs come back to center, you feel a brief release of tension."
Photo: Rony Shram