Get down on all fours on a mat or carpet. Lower yourself down to your elbows keeping them directly under your shoulders, palms facing down and pressing into the floor. Don’t let your head hang down or strain it upward; your neck should be aligned with your spine.
Tilt your pelvis under slightly to protect your lower back, and squeeze your inner thighs together so your legs form a V-shape [shown]. Keep your abs contracted as you breathe deeply, holding for 30 seconds. Try to work up to 1 1⁄2 minutes.
Another way to progress is to do a full plank: Extend your legs behind you one at a time, legs and feet together, holding your body in a straight line. Do 3 sets.
Benefits: Abs, butt, arms, legs and back, pelvic floor (Pressing your thighs together tightens your pelvic floor.)