While planks are great at improving spinal stability, the move doesn't factor in that when your body actually needs stability, 9.99 times out of 10, your arms, legs or both are moving, she says. That's what makes this simple yet dynamic exercise so functional: By working your core together with coordinated arm-leg movements, it will help you perform everything you do, both in and out of the gym, more safely and effectively.

How to do it: Lie down with your back flat on the floor, your hands and knees pointed straight up toward the ceiling and your feet in the air (your knees should be bent at 90 degrees). Press your low back into the floor and engage your core to maintain this flat-back position throughout the entire exercise. Slowly straighten and lower one leg while you move the opposite arm backward, over your head and toward the floor. When your straight arm and leg are parallel to and hovering slightly above the floor (or you cannot lower any farther), pause for one second then squeeze your abs to slowly return to the starting position. Repeat on the opposite side. That's one rep. Do two to three sets of six to eights reps.