Bulletin of the National Speleological Society - ISSN 0146-9517
Volume 32 Number 4: 89-115 - October 1970

A publication of the National Speleological Society

Human Biological Rhythms During and After Several Months of Isolation Underground in Natural Caves
Franz Halberg, Alain Reinberg, Erhard Haus, Jean Ghata and Michel Siffre


Speleologists have contributed invaluable data on human ciracian and menstrual rhythms, demostrating the persistence of these bioperiodicities over spans of several months of complete solo isolation from any or all known time cues. Under conditions of such solo isolation, including the absence of any direct interpersonal relations, statistically significant changes in frequency are demonstrated for both the circadian system and the menstual cycle. The desynchronization of the circadian sleep-wakefulness rhythm from a precise 24-hour schedule occurs as a statisticaly significant phenomenon even in the case of a group composed of members interacting with each other but isolated in a cave from their habitual societal setting.

In separate, but concurent, experiments two speleologists spent periods of three and four months, repectively, living in a cave in complete isolation from all external time cues. During this span observations on several periodic physiological functions, such as sleep-wadefulness, rectal temperature, urine volume, and excretion of posassium and 17-hydroxycorticosteroids were made. The data were subjected to a spectral analysis by computer techniques. Changes in various cyclic funcitons, interaction between different functions, and resynchronization at the end of the study are discussed. Comparision are made to an earlier study involving time-disruption due to intercontinental flights and to human isolation in a laboratory apartment. Other sudies of cave isolation are summarized and compared with the two experiments described. Justification for isolation studies in caves and for microscopic spectral analysis of the data is presented. The studies reveal that cyclical variation in environmental and social factors do not bring about human bioperiodic phenomena but are able to syncronize these bioperiodicities. Internal circadian and other time relations mapped during solo and group isolation provide a reference standard for assessing the effect upon human time structure of the many society influences to which individuals or groups are exposed in our habitual way of life.

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