Plank Hip Extension

From a forearm or straight-arm plank, lift one leg straight back a few centimeters, keeping it in line with your torso rather than letting it swing up toward the ceiling. Your hips stay level and square, if one side rotates up as your leg lifts, you have raised it too high. Hold the lift briefly, then lower with control and switch legs. The lift itself is small; the real work is resisting the rotation it tries to create through your core. Keep your neck relaxed and your gaze down at the floor throughout so your whole spine stays in one line.