The adoption of robotics in rehabilitation represents a smart solution to mitigate the physical workload of therapists and improve the consistency of motor task demonstration. This study presents the design and the preliminary experimental validation of a robotic system that physically demonstrates rehabilitative exercises. Three demonstration modalities were compared: a baseline video of a subject performing the task, and two robotic demonstrations using the TIAGo platform. In the latter, the robot reproduced rehabilitation tasks by replicating trajectories acquired in the joint space through Learning by Demonstration, either via hands-on kinesthetic teaching by an expert or from operational-space trajectories recorded with motion capture on healthy subjects. Performance was evaluated through objective physiological responses alongside subjective assessments using standardized questionnaires. Results suggest robotic demonstrators, particularly those based on joint-space control, are effective in conveying motor tasks and have high user acceptance.