The article gives a comparative description of the ultradian rhythms of workers in critical infrastructures in various conditions of professional activity. In connection with the need to conduct repair and adjustment work, workers in critical infrastructures carry out their labor activities, often migrating to areas remote from their permanent place of residence. The study of the relevance to the health and functional capabilities of the body of workers in critical infrastructures according to ultradian rhythms has not been sufficiently studied. The study used the software-statistical complexes “Varicard” and “HolterLive” in the statistical processing “ISCIM6.0”. The HRV indicators were studied in a group of ground service workers in the usual natural and climatic production conditions and in a group of landing on the Arctic islands to perform repair and adjustment work. Studies have established that both groups experienced an energy-deficient state, which reduces resistance and causes an overstrain of the adaptation mechanisms of the autonomic nervous system in controlling the regulation of the heart rhythm. The results of the study showed that intense workload in extreme conditions of extreme professional activity negatively affects the state of health characteristic of maladaptation.