An innovative concept and the structural organization of a modular system for long-term monitoring, analysis and correction of integrated health indicators of different groups of the population taking into account the impact of environmental factors and extreme conditions is described. The main elements of the system are a module for measuring physiological indicators that characterize the state of human health, a sensor module for selection and registration of environmental indicators, a data transmission module, a database, a module for comprehensive analysis of indicators, a forecasting module, a set of mathematical models, a module for results displaying. Methods of mathematical modelling and statistics were used to predict health state. The mobile application that allows to assign and take into account changes in environmental performance during physical activity, e.g. training weather conditions, such as temperature, relative humidity and wind speed, as well as the distance and duration of running, is developed. The results can be obtained numerically and graphically on the smartphone screen. The proposed system allows to predict the functional state of person in different environmental conditions. It will allow the user to make the right decision about the duration and intensity of physical activity in certain environmental conditions and choose the appropriate level of physical activity.