Basic Theory

The theory of biorhythms claims that one's life is affected by rhythmic biological cycles, and seeks to make predictions regarding these cycles and the personal ease of carrying out tasks related to the cycles. These inherent rhythms are said to control or initiate various biological processes and are classically composed of three cyclic rhythms that are said to govern human behavior and demonstrate innate periodicity in natural physiological change: the physical, the emotional, and the intellectual (or mental) cycles. Others claim there are additional rhythms, some of which may be combinations of the three primary cycles. Some proponents think that biorhythms may be potentially related to bioelectricity and its interactions in the body.

Basic rhythms follow certain facets of physiological cycles, though they may include others, and the details may vary depending on the source. The three classical cycles of biorhythms are endogenous infradian rhythms. The theory's basis lies in physiological and emotional cycles. They are often represented graphically as either symmetric or asymmetric waveforms, though most theories rely on symmetric forms. The most commonly used form is the sinusoidal waveform, which is thought to be a plausible representation of a bioelectric activity cycle. Due to this sinusoidal nature, the cyclical flow of bioelectric activity undergoes periodic reverses in direction. Each cycle oscillates between a positive phase [0%..100%] and a negative phase [-100%..0%], during which bioelectric activity strengthens and weakens. The waveforms start, in most theories, at the neutral baseline (0%) at the time of birth of each individual. Each day that the waveform again crosses this baseline is dubbed a critical day, which means that tasks in the domain of the cycle are far more erratic than on other non-critical days. The purpose of mapping the biorhythmic cycles is to enable the calculation of critical days for performing or avoiding various activities.

The classical definition (derivatives of the original theory exist) states that one's birth is an unfavorable circumstantial event, as is the day about 58 years later when the three cycles are again synchronised at their minimum values. According to the classical definition, the theory is assumed to apply only to humans. In the classical theory, the value of each cycle can be calculated at any given time in the life of an individual, and there are web sites that do exactly that.