Start in a push-up position with your shoulders directly above your hands. Lower your forearms and elbows toward the floor until your biceps make full contact with your forearms at the bottom. It’s tougher than it looks—most people struggle with it at first. A good way to learn the movement is to start from the bottom with your forearms resting on the floor, then push up from there.
To reduce the difficulty, pivot from your knees instead of your feet. To make it more challenging, elevate your feet on a step. If your wrists feel uncomfortable, try placing your hands on the edge of a step for better positioning.