Conservation of Angular Momentum and How it Relates to Quarterback

Do you know that figure skating can make you a better quarterback? Let’s discuss a crucial physics concept called angular momentum which is essential for rotational athletes.

What is angular momentum?

Angular momentum is the angular equivalent of linear momentum. Momentum can be thought of as “mass in motion”. The law of conservation of angular momentum means that momentum does not change unless an outside force acts on an object. Angular momentum is essential for rotational movements like the quarterback throw and can help increase the velocity of rotational movements.

Angular momentum = mass x velocity x radius

‍If mass stays the same, then radius can impact angular velocity. Radius goes up, velocity goes down. Radius goes down, velocity goes up. This means that rotational movements can manipulate the radius to increase the rotational velocity. This is why figure skaters hold their arms far away from their bodies to spin slower and hold them close to their bodies to spin faster.

How can you apply this to Quarterbacks?

With quarterbacks, the“radius” becomes the off-side arm. Going back to our equation of Angular momentum = mass x velocity x radius… if the quarterback’s off-side stays tight the torso can rotate through quicker, and when the off-side widens away from your body the torso will rotate through slower.

Here is an example of two different off-sides. The tighter one can generate more rotational velocity through the torso.

Simply put tight off-side = faster torso rotation.

Faster torso rotation equals more potential for velocity on the football. This is one reason why quarterbacks should not “clear” the off-side and pull their front-side arm away from their body. Not only does doing that result in a bigger radius and less rotational velocity but it also leads to loss of accuracy by pulling the head and spine with it.

What are correct off-side mechanics?

For a deep dive on this topic check out our off-side mechanics blog. With your off-side hand, you should initially work backward to close off the torso and create hip/shoulder separation. As you are accelerating though, you should keep off-sode tight to help with torso rotation speed.

Want to see how fast your torso rotation is? Join the lab and get access to this metric and over 20 other vital metrics for the quarterback throw.