8 rounds for time of:
Run 400m
Rest exactly 90 seconds between rounds.

Post total time including rest to comments.
Compare to last time here.

Six Factors in Running – stolen from CrossFit Verve
Gravity affects everyone the same. Even you. A smart runner will use gravity to his/her advantage. So, instead of using muscles to push off the ground, you shift your weight forward (basically, you start falling), and use gravity to initiate and continue forward motion.

Ground Reaction Force.
This refers to the strike of your foot on the ground. The harder the strike, the less momentum you carry, and the more energy you use trying to push off of the ground and propel yourself forward. If you push your center of mass forward and strike with the ball of your foot, you use less energy and run more efficiently.

Muscular Elasticity.
Your muscles’ elasticity is their ability to stretch or contract when force is applied to them. Fun fact: You have OODLES AND OODLES of muscular elasticity below the knee (Oodles is a technical term. Luke Palmisano, 2013 ™©) that sits in your calf, Achilles, and foot. But when you run with a heel strike, most of that elasticity lies dormant. Case in point: Try jump-roping on your heels. Not only would it be incredibly painful, it would be really hard. If you want to be a more dynamic runner, then run toe-heel.

Muscular Contraction.
This works with your muscular elasticity. Meaning, the more elastic and dynamic you allow your muscles to be, the less they have to contract. While you’re sipping your coffee or preferred energy beverage, take a moment and allow that to sink in. Basically, do you want to work harder, or smarter? Don’t answer that. Just say smarter for me and we’ll move on.

Torque is created when your center of mass passes beyond your base of support. When you fall forward to run, you create torque at the other end of your body. See, it’s all connected in some weird, cosmic, CrossFit kind of way. The more we lean forward to run, the more acceleration force that is applied with the feet (they move faster). That acceleration is torque being applied to the body.

Once you get up to speed, if you’re applying the five previous factors listed, it becomes easier to maintain that pace because you are using gravity and body positioning to your advantage. It’s like a car that you shift into a higher gear. The RPM’s actually go down, right? Same with your body.

This information is heavily referenced from the book Power Speed Endurance, by Brian MacKenzie.