A leg mechanism includes an articulated leg system (100), a passive device (130) and a cable (134). The articulated leg system (100) has a leg portion (128). The passive device (130) is coupled to the articulated leg system and is configured to apply a first force to a portion thereof. The cable (134) is coupled to the articulated leg system (100) and is configured to apply a second force, in opposition to the first force, to a portion thereof. When the cable (134) is drawn away from the articulated leg system (100), the second force moves the leg portion (128) in a first direction. When tension is released from the cable (134), the passive device (130) exerts the first force so as to move the leg portion (128) a second direction that is opposite the first direction.