Lie on your side with your legs extended and stacked, propped up on your forearm with your elbow directly under your shoulder. Lift your hips off the floor until your body forms a straight line from head to feet, then lower them back down with control, stopping just short of the floor between reps. The straight line is the whole exercise - your waist does the lifting, and your hips should never drift forward or roll back to cheat the angle.

Works: obliques, abs, glutes, shoulders

Breathing: Exhale as you lift your hips, inhale as you lower them.

Common Mistakes: Letting the hips sag or drop straight back to the floor between reps, rolling the chest toward the ceiling as the set gets hard, and letting the supporting shoulder creep up toward the ear.

Make Easier: Bend your knees and lift from the knees-down position, or reduce the range so the hips travel a shorter distance.

Make Harder: Hold for a 2-count at the top of every rep, raise your top leg as you lift, or move on to Side Plank Rotations to add movement at the top.