But when we have contraction, we basically move these z lines closer to one another. So when a contraction takes place, these z lines come closer to one another, so that the distance between the z line and this z line actually decreases. And what that means is this A band will also decrease. I'm sorry, this A band won't, but this I band will also decrease in size, as well as the h zone will decrease in size. But the A band, which actually includes the entire length of that thick filament will not change because the length of our thick filament does not actually change when our contraction takes place. So notice that when our muscle contracts, the A band does not change because the thick filament does not change its length, its size.