Relax in the push up position and slowly lift one fist up starting the movement from the solar plexus or from the shoulder if you rock when you lift one up. Shake the tension from it by letting the shoulder relax and the elbow relax and than the movement of the forearm twist out and than after you have cleaned out the arm let it sink to the ground again and repeat for the other fist. Do this a few times and remember to let the breath lead each movement and avoid the hurry to get somewhere. The purpose of the drill is to let the body move the arm rather than the arm moving when the body tenses up. You breath and move rather than move and breath.