A century of research on vital rhythms
Wilhelm Fliess proposes the 23- and 28-day biological cycles
Hermann Swoboda publishes his studies on psychic periodicity
Alfred Teltscher identifies the 33-day intellectual cycle
Biorhythms become a mass phenomenon in the United States
IBRA, the international research association, is founded in Atlanta
SRBR is founded: the study of rhythms becomes chronobiology
EBRS, the European biological rhythms society, is born in Frankfurt
Pioneers of biological periodicity
The first systematic observations of the 23- and 28-day cycles emerged between Berlin, Vienna and Saint Petersburg, at the crossroads of medicine, psychology and statistics.
Wilhelm Fliess
German physician and a central figure in the modern rediscovery of the 23- and 28-day cycles. His observations on biological recurrences are credited with the original framework of the theory of vital rhythms.
Hermann Swoboda
Psychologist at the University of Vienna, he observed systematic periodicity in psychic life and behaviour. His studies, parallel to those of Fliess, flowed into the classical formulation of the theory.
Alfred Teltscher
Professor of engineering at the University of Innsbruck. By statistically analysing students’ academic performance he proposed the 33-day intellectual cycle, completing the three-cycle model.
Nikolai Pärna
Estonian physician and researcher, among the forerunners of chronobiology. At the University of Saint Petersburg he studied the periodic swings of energy, mental activity and creativity.
The systematisation of biorhythmology
Throughout the twentieth century, mathematicians, physicians and researchers gave vital rhythms a formal structure: calculation tables, energy models and systematic treatises.
Eugenio Soriani
A key author of the theoretical framework: he introduced the concepts of qualitative energy platforms and biorhythmic potential, linking the basic vital rhythms to yearly cyclicity.
Alfred Judt
German mathematician at the University of Bremen, credited as the main rediscoverer of the 33-day rhythm. He formalised the Relative Mean Cyclic Impulses (RMCI) calculation tables, also cited in a NASA technical report on biorhythm charting.
Hans Früh
Swiss scholar and founder of the Basel Centre for Biorhythmic Studies. A pioneer of surgical biorhythmology, he studied how vital cycles relate to choosing the most favourable moments for operations.
Heinrich Kündig e Hans Künzi
Früh’s collaborators in Zurich, authors in 1954 of a study on the mathematical and astronomical relations between the 23- and 28-day cycles and the length of the civil year.
Livio J. Vinardi
Regarded as the leading modern exponent of biorhythmology, he distilled decades of theoretical and applied research into a rigorous model. He systematised the 23-, 28- and 33-day cycles, clarifying their applications to relationships, work and personal life. Founder of Biopsychoenergetics, his work is the most complete reference for compatibility analysis on biorhythmic grounds, and the research line our method builds upon.
Applied studies and observations
From factory floors to insurance statistics to the operating theatre: the vital cycles observed in the field.
Rexford B. Hersey
Researcher at the University of Pennsylvania (Wharton). In his studies of workers’ behaviour he observed periodic swings in energy and morale.
Hans Schwing
In 1930s Zurich he analysed hundreds of cases from insurance archives, observing a higher accident frequency on the so-called critical days of the cycles.
F. Wehrli
Swiss physician from Locarno who applied the biological cycles to clinical observation and to timing favourable moments for surgery.
The international spread
Between the Sixties and the Nineties, books, calculation kits and translations brought the three cycles to the general public, from the United States to Japan.
George S. Thommen
The reference populariser in the United States and IBRA Chairman from 1977. His Is This Your Day? (1964) brought the three cycles to the general public.
Bernard Gittelson
With Biorhythm: A Personal Science (1975) and Biorhythm Computers Inc. he led the American popularisation of biorhythms in the Seventies.
Walter A. Appel
German populariser: between the Eighties and the Nineties he devoted a series of books to applying the cycles in daily life, relationships and work.
Kichinosuke Tatai
Japanese physician who spread the theory across Asia, linking the cycles to health and accident prevention.
Ger Zantinge
Dutch author of Het goede moment (1976), a practical guide to the three cycles translated into several languages, Italian included.
Daniel Cohen
Author of introductory texts for the non-specialist reader, simple and concise, published between the United States and Latin America.
Peter West
With The Biorhythm Kit (1976) and later guides he gave beginners simple methods to chart their own cycles.
Walter Jung
Author of Biorritmos (1995), an introductory guide to the principles of the three cycles for the Spanish-speaking public.
Alberto G. Staffa
Following Soriani’s line, he applied comparative biorhythmic analysis to couples: fifteen case studies organised into balanced, semi-balanced and unbalanced profiles.
J. A. Vélez Rojas
His works include biorhythm calculation tables and studies on pregnancy and birth planning according to biorhythmic models.
Román J. Cano
Spanish-American populariser: he explained how to anticipate favourable moments in everyday activities, health and relationships.
Helene Kinauer Saltarini
Austrian author within the European tradition, with a focus on the 23- and 28-day cycles and on pregnancy-related themes.
Arnold Krumm-Heller
German physician and author active between the 19th and 20th centuries; he contributed in a popular key to spreading themes linked to biological periodicity.
Associations, study centres and calculators
Twentieth-century biorhythmology gets organised: international associations, research centres and a genuine industrial season of dedicated calculators.
IBRA
Founded on 7 July 1977 to promote studies, conferences and practical applications of the vital cycles. George S. Thommen served as its first Chairman.
IBUNA
Active in the theoretical study of vital rhythms, biopsychoenergetics and biorhythmic compatibility.
Centre for Biorhythmic Studies
Founded by Hans Früh, it promoted research on biological periodicity and on the medical and surgical applications of the vital cycles.
The calculator season
David N. Smith (International Horizons, Kosmos International) and Bernard Gittelson (Biorhythm Computers Inc.) brought cycle calculation into people’s homes: Kosmos I and II, Bio-Clock, Mini-Bio, Astro-Bio and personalised charts turned biorhythms into a cultural phenomenon.
References you can open
A selection of published work on biological periodicity: cellular clocks, seasonal variation, differences between people, and how performance shifts across the day.
A DOI is a scientific article's permanent code: it identifies that work for good, even if it moves site or publisher. Clicking it opens the publisher's page.
The 2017 Nobel Prize in Physiology or Medicine went to the discovery of the molecular mechanisms controlling the circadian rhythm.
Jeffrey C. Hall, Michael Rosbash, Michael W. Young. The Nobel Prize in Physiology or Medicine 2017. Nobel Prize Outreach
The clock inside a cell is a feedback loop between transcription and translation: a mechanism described down to the molecular detail.
Takahashi JS. Transcriptional architecture of the mammalian circadian clock. Nature Reviews Genetics. 2017;18(3):164-179
The oscillators are arranged in a hierarchy: a central pacemaker in the brain, and self-sustaining clocks in most cells of the body.
Mohawk JA, Green CB, Takahashi JS. Central and peripheral circadian clocks in mammals. Annual Review of Neuroscience. 2012;35:445-462
More than four thousand human genes shift their expression with the season, running in opposite directions in the northern and southern hemispheres.
Dopico XC, Evangelou M, Ferreira RC, et al.. Widespread seasonal gene expression reveals annual differences in human immunity and physiology. Nature Communications. 2015;6:7000
Thirty consecutive days of scanning the same person: brain networks reorganise across the menstrual cycle.
Pritschet L, Santander T, Taylor CM, et al.. Functional reorganization of brain networks across the human menstrual cycle. NeuroImage. 2020;220:117091
Across more than 55,000 questionnaires, sleep and wake times fall along a continuous curve: extreme early types wake up when extreme late types are going to sleep.
Roenneberg T, Kuehnle T, Juda M, et al.. Epidemiology of the human circadian clock. Sleep Medicine Reviews. 2007;11(6):429-438
A mismatch between the body clock and social schedules is associated with a higher body mass index, regardless of how much you sleep.
Roenneberg T, Allebrandt KV, Merrow M, Vetter C. Social jetlag and obesity. Current Biology. 2012;22(10):939-943
Systematic review across 43 studies and 231,648 people: the association is consistent in direction, but small in size.
Arab A, Karimi E, Garaulet M, Scheer FAJL. Social jetlag and obesity: a systematic review and meta-analysis. Obesity Reviews. 2024;25(3):e13664
Across thirteen human tissues, nearly half of protein-coding genes turn out to cycle in at least one tissue.
Ruben MD, Wu G, Smith DF, et al.. A database of tissue-specific rhythmically expressed human genes has potential applications in circadian medicine. Science Translational Medicine. 2018;10(458)
Meta-analysis of twenty-nine studies: endurance, power output, grip strength and jump height all vary across the day.
Knaier R, Qian J, Roth R, et al.. Diurnal variation in maximum endurance and maximum strength performance: a systematic review and meta-analysis. Medicine & Science in Sports & Exercise. 2022;54(1):169-180
In athletes, performance varies by up to 26% within a single day, and the best moment depends on time since waking rather than the hour on the clock.
Facer-Childs E, Brandstaetter R. The impact of circadian phenotype and time since awakening on diurnal performance in athletes. Current Biology. 2015;25(4):518-522
Attention, executive function and memory shift with time of day, and the effect depends on the chronotype of the person being measured.
Schmidt C, Collette F, Cajochen C, Peigneux P. A time to think: circadian rhythms in human cognition. Cognitive Neuropsychology. 2007;24(7):755-789
Across 56 people, early and late types show different profiles within the same day on vigilance, executive function and strength.
Facer-Childs ER, Boiling S, Balanos GM. The effects of time of day and chronotype on cognitive and physical performance in healthy volunteers. Sports Medicine - Open. 2018;4(1):47
Daily and seasonal mood rhythms detected across millions of public messages, in cultures around the world.
Golder SA, Macy MW. Diurnal and seasonal mood vary with work, sleep, and daylength across diverse cultures. Science. 2011;333(6051):1878-1881
Looking back distorts. Noting how you feel in the moment itself, rather than at the end of the day, reduces that distortion.
Shiffman S, Stone AA, Hufford MR. Ecological momentary assessment. Annual Review of Clinical Psychology. 2008;4:1-32
Studying a single person, repeatedly over time, is a recognised research design.
Lillie EO, Patay B, Diamant J, Issell B, Topol EJ, Schork NJ. The n-of-1 clinical trial: the ultimate strategy for individualizing medicine?. Personalized Medicine. 2011;8(2):161-173
What we get asked most
What is the difference between biorhythms and circadian rhythms?
Circadian rhythms are the roughly twenty-four hour cycles that govern sleep, body temperature, hormones and alertness. They are observed and measured, and in 2017 the discovery of their molecular mechanism was awarded the Nobel Prize in Physiology or Medicine. Biorhythms, in the classical sense of the word, are the three cycles of 23, 28 and 33 days counted from your date of birth: a reading of biological periodicity put forward between the late 1800s and the early 1900s. They are two distinct things, and on this page we keep them apart.
Are biorhythms scientifically proven?
It depends what you mean by the word, and a flat answer would be dishonest in either direction. That the body runs on measurable cycles is documented: the sixteen references gathered above are part of that record, covering cellular clocks, seasonal variation, differences between people and how performance swings across the day. The classical three-cycle scheme is a different matter: it is a historical reading of that periodicity, and we offer it as a frame for observing yourself, not as a prediction. The way to reach your own answer is the one its authors used, which is to look at your own days. Worth adding that this is not a cop-out: studying a single person, repeatedly over time, is a recognised research design (Lillie and colleagues, 2011), and noting how you feel in the moment rather than at the end of the day reduces recall bias (Shiffman, Stone and Hufford, 2008).
What are the three classical cycles?
A 23-day physical cycle, a 28-day emotional one and a 33-day intellectual one. The first two were proposed by Wilhelm Fliess in the late nineteenth century and taken up by Hermann Swoboda at the University of Vienna; the third was added by Alfred Teltscher in Innsbruck, who was analysing his students' academic results statistically. In the classical scheme all three start on the day you are born and run for life.
Are the cycles the same for everyone?
No, and the research is clear on this. A study of more than 55,000 people showed that sleep and wake times do not split into two groups but spread along a continuous curve: at the extremes, the earliest types wake up as the latest types are falling asleep (Roenneberg and colleagues, 2007). In athletes, peak performance depends on time since waking rather than the hour on the clock, and the same person's performance varies by as much as 26% across a single day (Facer-Childs and Brandstaetter, 2015).
Is there a best time of day to do things?
There is measurable variation, but no good hour that is the same for everyone. A meta-analysis of twenty-nine studies found that endurance, maximum power, grip strength and jump height all shift across the day, favouring the evening (Knaier and colleagues, 2022). On the cognitive side, attention, executive function and memory change with the hour, and the effect depends on the chronotype of the person being measured (Schmidt and colleagues, 2007). So the best moment is not an hour on a clock: it is yours.
What is couple compatibility based on?
On the classical scheme applied to two birth dates: the three cycles of two people are compared and you look at how they overlap over time. It is a frame for reading, not a prediction. It works as a starting point for observing your relationship in the reality of your days, and what you make of what you see stays with you.