Water immersion: analysis of diurnal rhythms of water and electrolyte excretion.

The biorhythmological structure of water-electrolyte metabolism was studied in humans during 7-day "dry" immersion. Results were processed with a set of mathematical methods in order to identify a parameter which would allow to obtain scientifically valid, reliable data without violation of any ethic constraints inherent to investigations with healthy test-subjects. Even this period of immersion gravely impacted functioning of kidney as an executive organ in the system of water-electrolyte homeostasis. Data of this study point to applicability of Cosinor analysis for quantitative assessment of fluctuation patterns in parameters of close to harmonical circadian rhythms, and variation analysis and normalized mean for rhythms of arbitrary forms.