The triggered stroke actuator comprises a cylinder (12) housing a movable assembly constituted by a piston (13), a rod (16) projecting from one end of the cylinder (12), and a slidable element (17) that is movable inside the cylinder (12). The actuator also includes means for propelling the piston (13) in response to a trigger command, and a return braking arrangement. The return braking arrangement is constituted by at least one ball (18) housed in an annular cavity (19) defined by the inside surface of the cylinder (12) and by the slidable element (17), a return spring (22) connecting the slidable element (17) to the piston (13), and a link element (23) connecting the ball (18) to the piston (13). The ball (18) is positioned by the link element (23) in a first segment (20) of the annular cavity (19) when the return spring (22) is relaxed, and in a second segment (21) of decreasing radial extent when the return spring (22) is compressed. Thus, the braking arrangement is released when the force applied to the piston (13) drops below a threshold value.