This paper features the development of a double-effect deformable actuator, conceived as the synthesis of a fluid muscle actuator and a pneumatic spring. The actuator is therefore able to exert both compression and tension forces. The paper describes the scheme of the actuator and the design solution adopted. Subsequently the results of experimental tests for the static characterisation are presented. The results show the compression and tension force of the actuator as a function of supply pressure and stroke. These experimental characteristics are evaluated, discussed and compared with the theoretical results provided by an analytical model. Finally, some possibilities for application and further development of the actuator are proposed.