ABSTRACT: Physiotherapy is a science which acts in the area of biomechanical and functional disorder, establishing diagnostics and supporting the locomotor system rehabilitation. These procedures require assistance of a physiotherapist, however they are insufficient for the country´s demand. Usually such procedures use devices with the newest technology, in order to enable recovery and avoid possible permanent trauma. In order to face this reality, we have committed to develop an air muscle, based on the McKibben´s model, with the purpose of proposing a new low-cost parallel robot to physiotherapy (Soft Robot) for the rehabilitation of patients with ankle injuries. This robot is responsible for moving three degrees of freedom platform, therefore acting directly in the rehabilitation of the patient through the execution of soft and accurate therapeutic movements that stimulate the recovery of operated tissues. First, it is build an air muscle that will be used as actuator in parallel platform. Then is raised a curve of behavior to shift versus pressure on proposed muscle. In conjunction with these data to actuator behavior is modelled and simulated the new parallel robot. This air muscle was build using a latex tube covered by a braided fibred mesh and fuelled by a pneumatic tire valve, therefore obtaining a nonlinear behavior of contraction to each pressure value admitted on muscle. By means of this prototype building purpose, we obtained satisfactory results, such as a contraction of 25% of the nominal length for pressures up to six bars. Considering such a result and the low cost involved building actuator as this one, the advantage in using this model is perceptible.