Currently, digital technologies are widely used to record any event by using different types of cameras, for different uses. There are cameras that use an optical sensor, which generates images in the RGB model. There are some cameras that use thermal sensors, which perform the registration of the temperature of the object being recorded and presents them under a color model using a color map. This research study uses a novel method to fuse optical and thermal images with the intention of being able to recognize certain parts of the human body. This study evaluates the presence of veins that have a higher temperature when performing rehabilitation exercises. The results allow to evaluate different combinations of color bands. In order to demonstrate the method, the use and application will depend on the analysis of the image and the interpretation by health personnel. At the time of merging the images, the optical image provides the structural part of the image, and the thermal image provides the functionality characterized by the body temperature. As a conclusion, this research study indicates that the proposed method can be applied to other applications in order to look for applications where the method can help in the diagnosis and evaluation of the treatment.