According to the proponents of the existence of biorhythms, a person's life is influenced by rhythmic biological cycles that would influence personal skills in various aspects, such as mental, physical and emotional.
These cycles start at birth and oscillate constantly (sinusoidal waves) in the course of life, so as to simplify the level of skills of a person in these areas with a mathematical model,
day to day. Sinusoidal behavior would be derived from hormonal and biochemical aspects, with their activities of biofeedback corresponding to chemical concentrations. br>
Most biorhythm models use three cycles: a 23-day physical, an emotional of 28, and an intellectual of 33. Although the 28-day cycle is the same length as the average menstrual cycle of women,
and was originally defined as a "feminine" cycle, the two are not necessarily synchronized.
Each of these cycles varies between high and low extremes, in a sinusoidal fashion, with days when the cycle crosses the line of zero, described as "critical days" at greater risk of uncertainty.