Biorhythm or circadian rhythm represents a biological process through which the human body adopts a rhythmicity, which can be measured once every 24 hours. An analytical analysis of human biorhythms and their interaction in the synergy of psychomotor capabilities of lawn tennis players was performed. The reliability of performances in official competitions is conditioned by the integral preparation of the athlete, the components of which are optimal technical and tactical, physical, functional and mental training, taking into account the manifestation of his biorhythms. Biorhythmology is currently of great theoretical and practical importance in sports training. However, certain principles and provisions of biorhythmology in sports are insufficiently highlighted and scientifically justified, but, without a doubt, research in this direction gives the expected practical result. A series of aspects of psychophysiology are highlighted, the solution of which largely depends on the success of using biorhythms to increase the efficiency of sports activities. The dynamics of the circadian rhythms of the psychophysiological functions are reflected in the volume and intensity of the applied training and competition tasks, as well as in the physical recovery after their performance. In order to identify the relationship between biorhythms and sports and psychomotor performances of athletes, we analyzed the results obtained in competitions by tennis students (the best and worst of the season). The analysis of the obtained results showed that the best sports and test results are presented by tennis players during the optimal phases of the biorhythm, and the worst - during critical periods. It is necessary to take into account the characteristics of the biorhythm when predicting and analyzing the performances of athletes in certain competitions and the test parameters that characterize their psychomotor capabilities as determining factors of sports and tactical abilities. It has been established that psychomotor indices and sports performance of tennis players are interconnected with the periods of biorhythms. In the negative period and on the critical days, the greatest decrease in the reactions to the moving object (RMO) was observed, the decrease in the state-impact force, which provides the force of the deep (postural) muscles of the trunk, involved in maintaining both statodynamic and dynamic, one of the factors of motor-coordinating qualities of tennis players.