The present invention generally relates to implantable medical devices, such as cardiac stimulators including e.g. pacemakers, and, in particular, to methods and systems for predicting patient responses to physical exertion, monitoring the patient response over time to evaluate disease progression and adapting pacing therapies of cardiac stimulators based on the predicted patient response. According to the invention, a current cardiac status indicator for the patient is created indicating a response of the patient to an increased physical activity as a primarily heart rate response or as a primarily a stroke volume response. The pacing parameters of the cardiac stimulator can thereafter be adapted depending on the current cardiac status indicator, wherein the adapted pacing parameters include a first pacing setting if the current cardiac status indicator indicates a primarily heart rate response or a second pacing setting if the current cardiac status indicator indicates a primarily stroke volume response.
