The article is dedicated to the problem of simulation of the functional activities of a human operator in the class of the additive system of representations, the main indexes of which are operational productivity during a shift and framing of the finished goods to the end. For the simulation the key moments were selected of the activity of a human operator, which determine the real operational productivity taking into account the processes of beginning of operation, getting tired, and restoration of his (her) functional abilities during an interval for rest. The obtained model allows us to establish an analytical relation between the productivity of a human operator and duration of the interval as a system guarantor for compensation for the fatigue. It allows us to control the course and results of the functional activities of a human operator due to the use of an additional potential of the functional activities of a human operator. Representation of the functional activity of a human operator must be considered with the use of the mathematical models with the interval parameters of the functional activity during the work shift, the influence on him (her) of such systemic factors as workplace organization, motivation to achieve the maximum performance, tiring process and recreational activities. The actual statistical data is based on timing of the activities and ergonomic studies.