It is proved that when choosing indicators to assess the fitness of athletes it is necessary to take into account their compliance with the stage of multi-year training, the specifics of the sport, sexual and other characteristics of athletes. Principles of the control should be based on the consideration of innate qualities and characteristics, dynamics of sports performance, diagnostics of the level of development and growth rates of special physical qualities, and other factors. The changes of the indicators characterizing the readiness of the rowers in the process of long-term training are investigated. According to the dynamics of performance and indicators of functional readiness, the characteristics that were evaluated are not unambiguous. Most of them are characterized by constant growth. Significantly lower number of indicators is characterized by relative stability in the process of long-term training. Some indicators have two distinct phases ¾ growth and stabilization. Different dynamics of indicators suggests that their use should be different in the process of sports selection and control. This puts forward certain requirements for assessing the fitness of athletes based on the results of testing: use in the process of selection and control, both conservative and variable; The second one is directly in the system of evaluation of the proposed indicators - the use of variational scales for assessing the fitness of athletes, taking into account age, combining conservative and variables. A fundamentally different approach should be used to compile assessment scales for the first and second groups of indicators. Stability of the indicators of the first group allows us to talk about the possibility of using in all age groups identical assessment scales, developed taking into account the distribution of the values of the indicators of the whole set of surveyed athletes. The variability of the indicators of the second group requires the development of assessment scales for different ages or different age groups of athletes.