Hold your fist in your palm and move it forward and backwards in wave strikes as the other arms resists. Do this slowly by letting the breath dictate the pace and feel where your elbow and shoulder are tense or where there is fear of movement. Shake your arms and neck afterwards and let the head move as a result of the body and shoulder movements. This way you will avoid head injuries from strikes and tension in the back and shoulders.
Do the same with the legs and relax your hips by going up and down without using your hands. (standing sitting)