The generalization of data from the modern literature on the studied problem, as well as the results of previous studies by Stankevych, Zemtsova & Tomilova (2018), allowed to justify experimentally the choice of blood urea to correct one of the metabolic processes in training athletes. As a result of the study of athletes found that at the starting mesocycle of the special-preparatory stage of the preparatory period, the rate of blood urea in both groups of athletes did not differ significantly and amounted to 4.05±0.082 mmol·l -1 and 3.68±0.084 mmol·l -1 in women and 3.97±0.091 mmol·l -1 and 4.68±0.045 mmol·l -1 in men, accordingly. This content of blood urea corresponds to the av- erage group norms and indicates the balance of anabolism and catabolism of proteins, and therefore, may indicate the state of recovery of athletes at the beginning of the mesocycle. However, the increase in this indicator at the end of the mesocycle indicates that the amount of training loads differs in the duration of work. However, both in ath- letic walking and in middle-distance runners, reliability was noted regarding the state of rest (p<0.01). Knowledge of the peculiarities of the functioning of this part of the metabolism and the development of ways to increase the effectiveness of this mechanism in terms of intense muscle activity should be considered as one of the promising research areas to improve training and competitive activities, as well as speed up recovery in athletes.