Muscle Reading is the art by which magicians perform an apparent ESP demonstrations by "reading" the involuntary movements and reactions of a spectator. The demonstration usually involves locating a hidden object (e.g. car keys, a check). The spectator, who knows where the object is, must concentrate in able for the demonstration to be a success.
There are two types of muscle reading. "Contact" muscle reading in which the magician stays in contact with the spectator by grasping his wrist or holding on object like a handkerchief between them. “Noncontact” muscle reading consists of having the spectator follow the performer about and having to "read" his hesitation patterns.
The art is also referred to as Hellströmism after Alex Hellström who made it popular early in the twentieth century. It has also been called Cumberlandism, after the English performer Stuart Cumberland.