Muscles exist in two forms: relaxed and loaded. Within the category of loaded muscles is the change in shape that occurs from being under load while extended and under load while fully contracted. Transient shapes, forms that appear and disappear, occur as the muscle moves from relaxed to loaded and from under load while extended to under load while contracted. These transient shapes are often the thin ends of the muscles, the insertions, that connect the muscles to tendons and bones. Tendons, while not muscles per se, can be treated as muscles when determining the exposure of shapes on the skin.