Not to be taken very seriously, but the idea of biorhythms has always interested me.
Thanks to - for a bit of background reading and further links see that site.

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The classical theory originated at the turn of the 19th century, between 1897 and 1902, from observational research.

The Physical and Emotional Cycles

Dr. Hermann Swoboda (Professor of Psychology, University of Vienna) was researching periodic variations in fevers and looked into the possibility of a rhythmic change in mood and health. He collected data on reaction to pain, outbreak of fevers, illnesses, asthma, heart attacks, and recurrent dreams, and concluded that there was a 23-day physical cycle and a 28-day emotional cycle.

Independently, Dr. Wilhelm Fliess (nose and throat specialist; reportedly a numerologist) was researching the occurrences of fevers, recurrent illnesses and deaths in his patients. He too came to the conclusion that there was a 23 and a 28-day rhythm. Fliess's theories were of great interest and importance to Sigmund Freud during his early work in developing his psychoanalytic concepts.

The physical rhythm cycle is responsible for strength, stamina, drive, confidence, energy, aggressiveness and courage.

The emotional rhythm cycle determines moods, optimisms, cheerfulness, creativity, well-being and emotional sensitivity.

The Intellectual Cycle

Alfred Teltscher (professor of engineering; University of Innsbruck, Austria) observed that his students' good days and bad days followed a rhythmic pattern of 33 days. Teltscher found that the brain's ability to absorb, mental ability, and alertness ran in 33 day cycles.

The intellectual rhythm cycle influences powers of reason, perception, acuity, judgement, decision-making and common sense.


Fundamentally biorhythms are a way of expressing continuous changes, each rhythm begins on the day you are born and follows its course throughout life and stops at your death.

Each rhythm has two stages (or phases), positive or high on the chart, and negative or low on the chart. The day of transition from one phase to the other is called a critical day, and they are very important, for it is then that we are most prone to accident, instability and error. During the days of transition (critical days) we become vulnerable, off-balance and our normal reactions are slowed down. This period may last for up to 48 hours.

Another Biorhythm calculator, with some interpretation, here

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