From:
http://wilderdom.com/games/PhysicalActivities.html
Recent work on the Involuntary Nervous System proves an explanation for this ideational part of this exercise and for the body/mind view generally. Miller (1969) says:
Cellular electric current can be made to occur in protoplasm by the very act of thinking. Thought alone can therefore, in and of itself, be the stimulus to induce an electric current to flow down any nerve to the affected tissue - demonstrating that thought is a source of energy...The Involuntary Nervous System is not necessarily involuntary...it is more under conscious control than previously believed.