Nowadays a computer is used as a main tool for many tasks. Usually a session using a computer in a computer center takes from 50 up to 150 minutes, getting the user to be tired. With this research, the dangerous positions adopted by the students in a computer center are analyzed and recommendations of exercises are listed. The exercises avoid the pain feel caused by those hazard positions. The suggestions are notified to the user by the Ergonomic-CBR application developed. After 40 minutes of a session with the computer, the Ergonomic-CBR application sends a test to user. With the answers, a case is formulated and the CBR cycle is loaded. The similar case is retrieved and adapted using expert-coded rules. All adaptations are done according to the pain feel. The result of the experiments done in Universidad de la Sierra, reflect that the students suffer of repetitive tension related with using computers. The experimental groups presented a diminution in stress and a huge acceptance of relaxation exercises proposed by the Ergonomic-CBR system.