The aim of the present StarTTproject is to develop the PACE-model and integrate it into a demonstrator, i.e., an algorithm/tool that quantifies the energetic reserve capacity of the body during exercise. The PACE-model integrates data registered during training (power output/speed or heart rate) and matches these data to the individual exercise capacity quantified by the Critical Power Concept (i.e., Critical Power and W’). Using this algorithm/tool, individuals performing exercise (patients, recreational and elite athletes) obtain realtime feedback on their energetic balance. Therefore, the PACE-model has broad application potential as it can be used to quantify the level of exertion during exercise/training, it allows to make immediate decisions with regards to pacing strategy (i.e., the intensity at which they are exercising), and it can help in the design of (interval) training sessions fitted to the individual. As such the PACE-model can be integrated or developed into a more mature training tool that strongly enhances the experience and efficiency of exercising, training and performing.