The CAREN project concerns the development of a virtual reality environment in which the agility of healthy subjects and patients can be tested in a variety of reproducible conditions. CAREN is made by customizing hardware and developing software to enable measurements of motion of a subject in detail as a response to a perturbation from the computer driven motion platform. After feeding the data in a human body model simulation, joint moments of force and muscle activation can be calculated. From the time patterns of these responses, inferences can be made concerning the motor programs the subjects launch. Any primary problem in a motor program, resulting in functional failure or inadequacy, can be identified down to the joint and muscle group. Secondary adaptations of patients to a limitation in the periphery (such as lack of muscle force) can be separated from the primary ones. Inadequacy of complete motor programs in children with movement disorders can be classified, recorded and related to progress that may occur. Especially the understanding of compensation strategies in patients may lead to a better therapeutic attitude. CAREN offers not only a test environment with means of almost unlimited exploratory behaviors for patients, but constitutes also a strong tool for motor control research.