Originating in the late 19th century, the theory of
biorhythms contends that a person's physical and
psychological states are governed by regular repeating cycles called "biorhythms."

Critical days occur when any of these cycles cross this midpoint. Your abilities and performance for a givencycle are said to be the most unstable on these critical days.

The three classic cycles are Physical, Emotional and Intellectual. In addition to these three primary cycles are the three secondary cycles, Mastery, Passion and Wisdom, which are composites
of the primary cycles.

It's fun to plot your own biorhythms to see if you feel that they reflect your daily feelings and abilities. It's also fun to plot the biorhythms of others to see when you are supposed to be compatible and in "synch".