The present invention relates to a system (1) for estimating cardiovascular fitness of a person, comprising a heart rate monitor (10) for acquiring a heart rate signal including information about the heart rate of the person, an activity monitor (20) for acquiring an activity signal indicative of physical activity of the person, a classifier (30) for classifying the activity of the person based on the acquired activity signal, a selector (40) for selecting one or more heart rate features obtained from the acquired heart rate signal based on the acquired heart rate signal and the classification of the activity for use in an estimation of the cardiovascular fitness of the person, and an estimator (50) for estimating the cardiovascular fitness of the person based on the one or more selected heart rate features
