Lay down on your back, clasping both hands behind your head. Cross your ankles and bend your knees, letting them open to the sides, and lower your feet so that just your toes are lightly touching the floor. Brace your abs in tight and crunch up, lifting your legs and hips off the ground as you bring your head and shoulder blades off the floor, trying to touch your elbows to your knees at the top. Slowly lower back to your start position, using your abs to control your movement. Do 15 reps in a row.
Sit on your mat with your knees bent and feet lifted off the floor, holding the ends of one dumbbell with both hands. Brace your abs in tight and lean back slightly. Rotate your body to the right and tap the dumbbell on the mat just outside your right hip, then quickly rotate left and tap. That's one rep. Do 10 reps in a row.
At-the-gym version: Med-ball Russian twists and reverse curl
Photos by Vanessa Rogers Photography were shot on location at Canyon Ranch Miami Beach