A procedure and apparatus to determine the overall fitness of a test subject. For this purpose the qualitative and temporal progression of the heart rate under constant physical stress of the subject is prescribed with at least one parameter dependent on the subject. The heart rate of the subject is measured under constant physical stress during a period of time. The parameter(s) are determined from the measured values, and the maximum heart rate and/or the initial heart rate and/or the increase characteristic of the heart rate are determined from the function and the measured values by numerical procedures. The apparatus can measure the heart rate of the subject, record a temporal progression of the heart rate under physical stress, and determines numerically from the temporal progression of the heart rate, the maximum heart rate and/or the initial heart rate without physical stress and/or the increase characteristic of the heart rate.