Objective: determination of criteria for assessing functional reserves and reliability of voluntary movement control system under various conditions of muscular activities. Material: Students aged 17-19 and athletes aged18-27 and specialised in various sports events participated in different studies. At Physical Education classes, female students were engaged in a programme aimed at improving the reliability and reserving the control system of local and regional movements of different coordination complexity. Athletes – cyclists, wrestlers, weightlifters, shooters performed specialised movements of different coordination complexity in the process of adaptation to specific physical loads in each sports event. The quality of motor regulation demonstrated by cyclists, weightlifters and wrestlers was analysed according to muscular activities, intermuscular relationships during muscular performance manifestation in the process of cyclic and acyclic loads, whereas shooters performed it according to the result of shooting at a target. Results: It has been revealed that in the process of a long-term adaptation to various types of muscular activities, the reserves of the movement control system representing different coordination structure are characterized by: an increase in the power of compensatory rearrangements to maintain the motor function reliability in complicated conditions of motor regulation and, in particular, during functional deprivation of the key sensory systems, maximum activation of physiological systems in the process of muscular activity and compensated phase of developed fatigue. The most prominent changes occur in movements, in the control of which the highest levels of regulation are involved. In movements regulated at lower motor levels, the shifts are less significant. Such movements are more stable, programmatic and harder subjected to change by means of physical exercises. Conclusions: The key criteria for the reserve capacities of the movement control system are as follows: power, efficiency and interchangeability of compensatory responses and mechanisms ensuring the reliability of movement control under the influence of distorting factors and fatigue; speed of transition to programme mechanism of motor regulation in the process of improvement under stable functioning conditions; manifestation of the "afferentation narrowing" principle in the sensory control of movements under stable functioning conditions.