Hibernation is a process of vital importance to organisms that during extreme winter temperatures do not have the ability to migrate. Characteristics of all hibernating organisms are reduced metabolism, lowering body temperature, increased fat usage and a lot of adjustments that differ between individuals. Mammalian hibernation is one of the most complex forms of natural hypometabolism because organisms are not only in period of torpor but also periodically they inhibit their own thermogenesis, which allows drastic drop in body temperature. Those processes are used for the purpose of human cryogenics researches, which promises a lot in the future especially from biotechnological applications to medical ideas regarding extending the human lifespan. Cryogeneses would allow entry into a torpor where physiological and biochemical activities are suppressed, energy consumption is minimal and as desired, and returning to normal life in the desired moment. However, to achieve such a desire, it is necessary to study large number of hibernation models and to associate their adaptations with possible applications to humans. Two very different models useful for the research regarding the adjustments to hibernation are the Arctic ground squirrel and the American black bear. Although each organism has developed its own adaptations, the common feature of both models is survival in conditions of reduced oxygen concentration. This adaptation is possible because both models lower heart beating rate, which results in reduced metabolism and decreased oxygen demand. The Arctic ground squirrel has adjusted heart rhythm to the lowered heart beating rate, but American black bear did not develop this adaptation so that is the reason why he experiences strong variations in heart rythm. The aforementioned adaptations and a set of regulatory molecules participating in hibernation processes, with additional engagement and research, can be applied to human cryogenic processes and the advancement of medical services.