The primary aim of the project was to create a mobile application that will help target group (athletes aged 12-15 and their parents and coaches) to diagnose fatigue early. The application will work with a unique algorithm that will take into account the relationships between variables and also the variables weight of individual factors. The algorithm were based on the heuristic scientific information and measurements in the project. Subsequently, mobile app. categorize athletes at risk of fatigue and then it provides further steps in the management of fatigue.The major outputs was be reached in October 2021.