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Protecting ACLs: Why deceleration matters

Our in-house medical expert, Aaron Borgmann, addresses a major issue across the NFL.

Kansas City Chiefs v New England Patriots Photo by Maddie Meyer/Getty Images

Editor’s note: ACL injuries ruining seasons is a growing problem across the NFL. I asked our own Aaron Borgmann to write about how these types of injuries could be prevented.


Most people don’t realize it, but with athletes, there is definitely a science to the act of stopping, or decelerating. The topic is impossible to cover in one brief article.

However, with the NFL resuming and ACL knee injuries again making news, this is a good opportunity to educate on this important topic. The anterior cruciate ligament (ACL) is one of the two main ligaments on the inside of the knee that are critical in the stability of the joint.

At the time of this writing, there have been eight reported athletes with ACL injuries already this preseason. There is a strong link between athletes decelerating from a high speed and the occurrence of ACL injuries. Therefore, the purpose of this article is to describe why being able to decelerate with efficiency and power is important.

First, we need to omit contact injuries from this discussion when considering ACL injuries. These cannot be predicted or prevented. To my knowledge, there is not a brace company in the world or a training methodology that would claim they can prevent a contact ACL tear.

That leaves us with the nasty looking, non-contact, open field or jumping-and-landing ACL injuries. You know these. The ones that you see as players go down in a heap as they either try to change direction, land awkwardly or even while celebrating with teammates.

First, preventing a season-ending ACL injury from a pre-hab standpoint is difficult; however, in certain populations, it does have its advantages. For example, there is more and more pre-hab being done in youth sports, especially in females. Females are more prone to this type of injury due to body differences such as hip angles and increased levels of hormones that allow for more joint laxity. Thus, it is important to learn how to decelerate and land properly and accept the load being put through the knee.

From a rehab or performance angle, after an ACL injury, when someone is mastering the art of changing direction, there is a learning curve on figuring out how to decelerate again. I’ve always been taught and noticed that the best players in any sport take the least amount of time to change direction. In other words, they decelerate the best – think of it as stopping with speed. At the NFL level, this is fractions of a second, but it is noticeable.

We see it all the time in rehab: when people learn to slow down and control their body again after an ACL reconstruction, they often lean too much away from the direction they want to go because they are not strong enough or have enough confidence to control their body through the decel portion of the movement. Think of trying to move one way but having an imaginary rope pull you the opposite. Obviously, this is critical to overcome to return to the field with any level of success.

Time and time again, an athlete would state that they feel good and are ready to perform a change-of-direction activity, but then when asked to do so, they struggled with it. Often, they were not ready (or had not been properly taught) to decelerate. Part of my job is to prove to them: 1) that they aren’t ready for this but then 2) make them understand the steps it takes to be ready again.

This begins by simply making sure that the athlete understands the task being asked of them and explaining the exercises thoroughly, so they get the goal of the activity. Telling someone just to jump up or down on a box isn’t going to cut it. They need to make sure they understand why they need to land with strength and stability and how to execute the task. Simple double leg and single leg jumping can often get people moving down the correct path of decelerating with strength.

A good way to have a football player understand this is to have him jump onto or off of a simple two-inch box and prepare to be pushed in any direction. Controlling the landing and getting ready to accept outside force helps them learn what it means to stop with power. One looks for landing form, loss of balance in any direction or hesitation. Once they feel and master a simple task such as this, you can progress to changing direction, forces, box height or legs It doesn’t need to be complicated, they just need to feel stable when doing the activity.

Progressing to the next level is easy. Starting in open space, have a player hop back and forth from right leg to left leg and hold the position on one leg, thus accepting the force and controlling it again, looking for abnormalities. Once they begin to feel this on a rehabbing joint it becomes much easier for them to perform a change of direction movement in real time and at increasing speed. It’s a fancy term we call proprioception, or knowing where your body is in space.

The steps of rehabbing an ACL with regard to deceleration sound fairly straight forward, but to get a player to understand it and subsequently perfect it takes time and reps, lots of reps. Patience is rewarded here, and quality reps are preferred over just going through the motions. Those athletes that have been re-trained on how to land and change direction with power and control have much better outcomes coming back from ACL surgery and are noticeably better than those that have not focused on it.

Obviously, this is a very brief look into the subject, but keep an eye out for this as the pre-season moves forward, especially if your favorite player is coming back from an ACL injury.

Watch how they move and see if they have mastered the science of stopping with speed again.


Aaron Borgmann is the founder of Borgmann Rehab Solutions. He spent 12 years in the NFL as an assistant athletic trainer and physical therapist before joining Arrowhead Pride.

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