And that's exactly why our bicep is an extensor in this case. So we see any given muscle can act as an agonist but it can also act as an antagonist. By the same token, it can act as an extensor but it can also act as a flexor in other cases. So when we flex, this acts as our flexor. When we extend this act as our extensor as described just a moment ago. So we see muscles by themselves do not actually create the motion.