An employee was showing another employee how to shut off a stud machine when the cable on the stud machine arced. The employee reacted by jumping out of the back of the trailer (height of approximately 4.5 feet). His foot became caught on the ladder, causing him to land awkwardly on his arms. He suffered a fractured radial head on his left arm, as well as a broken radial head and dislocated elbow in his right arm.