The present invention generally relates to a non-invasive biosensor device configured to measure physiological parameters of a subject. In one aspect, a method of determining a training threshold of a subject is provided. The method includes the step of detecting an oxygenation parameter of a tissue of the subject using Near InfraRed Spectroscopy (NIRS). The method further includes the step of processing the oxygenation parameter. Additionally, the method includes the step of determining the training threshold of the subject using the result of the processing. In another aspect, a biosensor device for determining a lactate threshold of a subject during exercise is provided. In a further aspect, a biosensor device for measuring parameters of a subject during exercise is provided.
