Abstract
Two groups of recruits were examined at a navy training center in the North-European Russia. Group 1 comprised 37 conscripts from the southern regions of Russia. Group 2 comprised 37 conscripts from the northern regions of Russia. The objective of the examination was to determine the specific features of variability of heartbeat of military men during the initial period of their service under northern conditions. A «Polar» heartbeat monitor was used for rhythmocardiographic recordings. Heartbeat variability was analysed by quantitative assessment of histograms using simple statistics, spectral analysis, and wavelet analysis. In Group 1 recruits, changes in heartbeat regulation observed from the first through the fifth month of service were attributed to an increase in the sympathetic tonus of the vegetative nervous system. In Group 1 recruits, the first three months of their service were associated with an appreciably high tonus of the parasympathetic system; however, starting from the fourth month, manifestations of an increase in the influence of the sympathetic branch of vegetative nervous system on heartbeat were found.
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