1. A device comprising: an input component configured to select a single or multiple regions of interest from an image of a subject's hands or arms or a background of the image of the subject's hands or arms, or a stationary region from a background; a processor component configured to identify and track spatiotemporal characteristics of at least one region of interest (ROI) on an image of the subject's hands or arms without application of sensors or other instrumentation to the subject's body, wherein the processor, in operation, is configured to: identify motion of the ROI; perform cyclic motion analysis on the ROI; quantify kinematic properties of the ROI, said kinematic properties comprising velocity, acceleration, and spatiotemporal characteristics; ascertain a duty cycle of the subject's forceful hand exertions from threshold level crossings of the kinematic properties of the ROI and repetition frequency of a task being performed by the subject; and an output component configured to provide information from the processor about the repetitive motion and hand exertions of the subject comprising repetition frequency, duty cycle, and hand activity level (HAL) of the subject for preventing injuries due to repetitive motion or muscle fatigue.