Global warming affects people’s daily life, reduces endurance and work capacity. The purpose of our study is to investigate the functional capabilities of the circulatory system, adaptation potential and stress resistance of individuals with different heat sensitivity. To evaluate the activity of the cardiovascular system, an echocardiographic examination was performed. The reserve capabilities of the heart and the economy of its work were determined using the Robinson index and the Roufier test. Resistance to hypoxia was determined using the Stange and Genchi tests. The degree of oxygen assimilation was evaluated according to the values of maximum oxygen consumption. Cardiorespiratory fitness was determined based on the results of the Rufier test. Adaptation potential was established according to Baevsky’s method. Stress resistance was assessed by determining the response index of the cardiovascular system to psycho-emotional stress. It was established that in people with lower heat sensitivity, the activity of the cardiovascular system is more optimal and more economical and its reserve capacity is greater, compared to higher sensitivity individuals, in which the intensity of its work in an uneconomical mode is increased and the reserve potential is limited. Shorter breath retention time on inhalation and exhalation, respectively, in persons with higher sensitivity to heat indicates a worse oxygen supply to the body. Also, they have a poor ability to absorb oxygen and lower cardiorespiratory efficiency. The predominance of stress adaptation mechanisms and lower stress resistance were also revealed. Thus, our results show that individuals with a higher sensitivity to heat are particularly vulnerable to the negative effects of global warming, which should be taken into account for the prevention of cardiovascular and heat diseases in them in the future.