Flexibility is defined by Gummerson as the absolute range of movement in a joint or series of joints that is attainable in a momentary effort with the help of a partner or a piece of equipment.. This definition tells us that flexibility is not something general but is specific to a particular joint or set of joints. In other words, it is a myth that some people are innately flexible throughout their entire body. Being flexible in one particular area or joint does not necessarily imply being flexible in another.