Within the present study, an analysis is carried out of the distinctive features of the training preparation process of young basketball players conceived as a multidimensional dynamic system. The central focus is the coordinated coupling of indicators of external and internal training load with sleep parameters and heart rate variability (HRV) for the purpose of enhancing the controllability of adaptive responses and of purposefully refining technical and tactical competence. Drawing on systems methodology and on the processing of longitudinal data arrays, the work examines the role of autonomic tone in the formation of cognitive and motor functions in athletes in the under-13 (U13) category. As the instrumental core, mathematical constructs of the stimulus–response class (including the Banister model) are considered, alongside contemporary machine-learning methods (LSTM, random forest) applied to predict functional readiness and the likelihood of developing overtraining. The obtained results underscore the determining significance of sleep quality as a mediating link that connects training stress with indicators of sporting effectiveness manifested in the accuracy of shooting actions and in the productivity of spatial positioning on the court. The formulated concept substantiates the necessity of shifting from episodic control to continuous management of the athlete’s state, implemented on the basis of real-time feedback loops.