A sensor system is for determining a breathing type of a subject. It has first and second electromagnetic radiation (e.g. optical) sensors, for example PPG sensors. The sensors are for application to the skin of the subject at different sensor locations. The signals from the first and second sensors are analyzed to determine if there is predominantly a first breathing type (e.g. chest breathing) or predominantly a second breathing type (e.g. belly breathing), or a mixture of the first and second breathing types.