Participants are asked to walk in the lab while cameras record their movement. During this test, subjects wear a t-shirt and shorts with their arms and legs wrapped with a soft, rubber-like material. A piece of firm material is attached to the rubber sleeves and small plastic reflective balls are attached to the firm material. Balls may also be attached to the skin, using an adhesive. With the balls in place, the subject walks several times while cameras record the positions of the balls. In addition, small metal electrodes attached to the skin with an adhesive measure the electrical activity in the muscles.