According to the National Center for Biotechnology Information, it is sometimes possible to see skin rise and fall in the arms and legs as a result of a normal pulse. The visual pulsation occurs in arteries rather than in veins.
Cardiologist Dr. Bennett Werner points out that pulsing is often visible in the radial artery on the inside of the wrist. Sometimes this occurs as a result of a bulging of the blood vessel. Typically the bulging disappears when the arm is raised over the level of the heart. If there is no pain associated with visible pulsing, it is most likely normal. Dr. Mitchell Vogel advises that if the visible pulsing is associated with an unusual rapid heartbeat, pain or other cardiac symptoms, a doctor should be called.