Biological Rhythm Overview: Ultradian, Circadian and Infradian Classification

First published: 2020

Brief summary

Reference overview classifying biological rhythms by period length -- ultradian (seconds to hours, e.g. cell division, REM sleep cycles), circadian (~24 hours), and infradian (days to years) -- with the mathematical definitions used in chronobiology (MESOR, amplitude, acrophase).

Article

Biological Rhythm Overview: Ultradian, Circadian and Infradian Classification is a reference overview published by ScienceDirect Topics in 2020. It provides a reference overview that classifies biological rhythms by period length -- ultradian (seconds to hours, e.g. cell division, REM sleep cycles), circadian (~24 hours), and infradian (days to years) -- with the mathematical definitions used in chronobiology (MESOR, amplitude, acrophase).

The analysis focuses on ultradian (seconds-hours), circadian (~24h), infradian (days-years). It also considers defines period as 1/frequency and gives the standard chronobiology terminology (MESOR, amplitude, acrophase). This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: Rhythmicity can be observed over the entire range of time scales from fractions of a second to years, but can be broadly grouped into three categories: ultradian, circadian, and infradian, with the period equal to 1/frequency. The interpretation is strongest when sample selection, age, physiology, measurement error and individual variability are accounted for.

For cycles researchers, the article brings together biological rhythms, ultradian rhythms, circadian rhythms, infradian rhythms. It is relevant to biological cycle research because living systems contain interacting clocks and rhythms whose periods vary with physiology, age, environment and measurement method.

Because this is a reference overview, it is best used as an accessible introduction or perspective rather than as conclusive evidence. Forum discussion should follow its references back to the primary data and original research wherever possible.

Source details and credits

• Source / publisher: ScienceDirect Topics
• Source type: Reference overview
• URL type: WWW
• Credits: ScienceDirect Topics
• URL: https://www.sciencedirect.com/topics/neuroscience/biological-rhythm