The present article was designed to report the results of the investigation into various non-specific adaptive reactions of the organism (NARO) based on the determination of the ratio of lymphocyte to neutrophil levels in the blood of the athletes under conditions of high-intensity training. We evaluated the frequency of different types of adaptive responses in the biathlon skiers at different stages of their annual training cycle. The study has demonstrated the relationship between metabolic changes under the influence of training and the type of adaptive responses. It is concluded that the adaptive stress responses are associated with the increased "metabolic cost" paid for the performance of strenuous exercises which can be a cause of slowdown of the adaptive processes and lead to overtraining.