According to an example aspect of the present invention, there is provided a system for heart rate monitoring of an object, the system comprising means for measuring heart beats of the object with a first unit at a first sampling rate, determining a heart rate, determining a time difference between consecutive heart beats, determining a time of each heart beat, or determining at least a part of a wave form of a heart beat signal, wherein the first unit includes further means for changing the sampling rate as a response to the determined information.
