an extensile fluidic muscle actuator that changes the normal direction of force and motion , achieving compressive force generation and extensile motion output with just a small increase in friction , weight , and cost is disclosed . the motion conversion is accomplished by a pushrod that is attached to the inside end of one of the actuator &# 39 ; s end fittings , and extends through the actuator body and slidably out through the other end fitting . the other end fitting is held stationary by a seal housing that contains a sealing element to retain internal fluid pressure as the actuator moves . a linear bearing may also be installed to keep the rod aligned and centered properly in the seal . upon pressurization of the actuator , the flexible body of the actuator will expand radially , causing relative contractile motion between the two end fittings . however , as the two end fittings are drawn towards each other , the pushrod is extended .