In an implantable medical device, such as a cardiac stimulator such as a pacemaker, and method for predicting patient responses to physical exertion, the patient response is monitored over time to evaluate disease progression and pacing therapies of cardiac stimulators are adapted based on the predicted patient response. 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.
