This exercise is a unique core-strengthening exercise that targets your abs and obliques, while increasing mobility in the shoulder and upper back regions.
Get into the pushup position with your hands shoulder-width apart directly beneath your shoulders. Drive one knee towards your elbow and rest it firmly against your arm.
Brace your core and slide your knee down your foreman toward your wrist. Pause. Keeping your core strong, pull your knee back up your foreman until it reaches the elbow. Return leg back to the starting position.
Do not rotate the torso. Instead, keep shoulders and hips parallel to the floor throughout the exercise.