A heart rate sensing module configured to be fixed on a wearable device intended to be worn by a user, the module comprising:- at least one contactless sensor adapted to sense at least one parameter indicative of the distance between at least a reference point of the skin of the user and a reference point of the module when the module is fixed to the wearable device when worn by the user in such a manner that the contactless sensor is distant from the skin of the user,- at least one communication entity adapted to communicate data indicative of the at least one parameter sensed by the at least one sensor to a heart rate determining component.
