Today, accurate sport-specific performance indicators can only be obtained at considerable costs. Archinisis transforms athletes’ raw motion data into precise key performance indicators which can be immediately analysed through an easy-to-use tool. Our solution is based on a single sensor worn on the athlete’s upper back coupled with algorithms specially developed for individual outdoor elite sports. We use biomechanical models and motion constraints to automatically monitor athletes' movements. Coaches obtain highly accurate sport-specific performance indicators within seconds to fully exploit the athlete’s potential, avoiding tedious data review and video analysis after each training.