A rehabilitation device for a rehabilitation exercise. The device comprises at least one marker configured to be attached to at least one body part of a subject. The device comprises an image capture unit configured to capture a first image of the at least one marker at a first position and a second image of the at least one marker at a second position. The device comprises a processor configured to receive the first image and the second image from the image capture unit, identify a first region of interest (ROI-1) of the at least one marker in the first image, identify a second region of interest (ROI-2) of the the at least one marker in the second image, compare the first ROI (ROI-1) with the second ROI (ROI-2), and output data based on at least the comparing results. A computer-implemented method is proposed for rehabiliatation exercise. A computer program product is proposed for operating a rehabilitation device
