A medical training manikin (1) to simulate spontaneous breathing, comprising a torso containing at least one pneumatic actuator (3) for obtaining raise of the manikin's chest or stomach. The actuator (3) is connected to an accumulator (7) via a control valve (5), which is designed to let air from the accumulator (7) into the actuator (3). The accumulator (7) is designed to be temporarily connected to an external pneumatic source (8) for filling of the accumulator (7) with a pneumatic pressure adequate for repeated actuations by the actuator (3).