The answer is ‘they create tension by pulling toward opposite poles’. Kinetochores change between persistent phases of movement towards the pole (poleward) or inversed (anti-poleward), which are coupled with alternating states of kMTs (kinetochore microtubules) depolymerization and polymerization, respectively. A low tension at kinetochores promotes change towards kMTs depolymerization, and high tension promotes change towards kMTs polymerization.