My research work in the 'Active Lifestyle' track of 'Lectoraat Move to Be' involves the design process of feedback principles aiming to improve the technique of sport skills. These feedback mechanisms are based on (i) measuring relevant technique key points, (ii) real-time analysis and interpretation of the measured data, and (iii) translation into relevant, meaningful, and understandable feedback, instruction, and cues for the user. The focus is to design feedback that fits modern motor-learning principles, thus promoting an external focus of attention and autonomy of the user to improve both technique and motivation. Running is used as the first context to design these feedback principles.