Muscles involved: Abdominal external oblique muscles.
Execution: Straighten up with your feet slightly wider than your shoulders. Extend your arms to the sides. Your right foot looks outward, and your left foot is turned at 90 degrees to your upper body. Put your right hand on your right shin, and, by keeping your back straight, raise your other arm. At the same time, move your pelvis backward and down. Repeat the exercise on the other side.