Do it: Lie on floor with feet in air, hips and knees bent 90 degrees, pressing lower back down. Press your palms and knees together; hold, maintaining resistance, for 30 seconds. Extend one leg until heel hovers one inch above floor. Alternate back and forth. Continue for 30 seconds.

Trainer notes: “If you feel your pelvis shift as you’re pressing your legs forward and down, you’ve gone too far,” cautions Giordano. “If it feels off, make this easier to execute by not lowering your legs as far toward the ground.”