Alright, let’s compare these two races. On the top, we have the 12.90 NCAA Finals performance, and on the bottom, the 12.75 preliminary race.

One of the biggest differences I see is what the right arm is doing over the hurdle.

In the 12.90 race, watch how the right arm works across the body. The right and left arms almost become linked together. When the right arm moves, it ends up pushing the left arm out of position, creating extra rotation through the shoulders and torso.

Now, that may not seem like a big deal, but in hurdles, every unnecessary movement has a cost. Because of that excess rotation, he’s not able to get back to sprint mechanics as quickly when he lands. Instead of coming off the hurdle and immediately attacking the ground, he has to spend time correcting that rotation before he can fully accelerate.

Now compare that to the 12.75 race.

The right arm is much cleaner and more compact. It stays within its lane and doesn’t interfere with the left arm. As a result, the shoulders stay more stable and square to the direction of travel. That allows him to come off the hurdle running sooner and transition back into sprint mechanics much more efficiently.

Watch the first few steps after touchdown. In the 12.75 race, you can see that he’s already back into sprinting almost immediately. In the 12.90 race, there’s a slight delay because that upper-body rotation has to settle before he can reestablish efficient sprint mechanics.

At this level, we’re talking about very small differences, but those small differences add up over ten hurdles. The cleaner arm action in the 12.75 race helps him maintain velocity between hurdles, while the extra rotation in the 12.90 race creates just enough disruption to cost valuable time.

So if I had to point to one major technical difference between these two performances, it would be the right arm’s interaction with the left arm and the effect that has on body rotation and the ability to get back to sprinting efficiently after each hurdle.