Copenhagen Planks (short and long lever) primarily target the hip and groin muscles (also known as the adductors), however, they are a great exercise for the core muscle too.

Position yourself in a side plank position on your right forearm with your left knee resting on the top of an exercise bench, step or chair. The 'lever' is between your hip and your knee. Your right knee can be bent or extended underneath a bench. Keep your shoulders, hips, and foot in a straight line, as you push down with the left knee, feeling the tension in your adductors.

Keep a strong core and your pelvis tilted forward to keep a flat back. If you don't have a step, use a pile of books or the bottom step of a staircase.