Newton’s Second Law of Acceleration and why understanding it can prevent injuries

Newton’s Second Law of Acceleration and why understanding it can prevent injuries

When I train clients, I am constantly repeating the importance on isolation exercises to not use momentum. The goal is to slowly isolate a specific muscle and not engage the surrounding muscles. It is very important that you know what muscle you are supposed to be working and how to engage it; however, not “cheating” is also very important for injury protection.

From a more scientific view, I am talking about Newton’s second law of acceleration that states that the force acting on a body moving in a given direction is equal to the body’s mass multiplied by the body’s acceleration.

Why is this “law” important for injury prevention?

Well, if you “cheat” by initiating a movement with momentum from a body part other than the one you are focusing on, the momentum of the moving weight may be greater than the muscle’s ability to decelerate and stop it. The “stopping muscles” may not be strong enough to match the force involved and this exposes ligaments, muscles, and the joints to over-stress and injury.

For example, if you do a bicep curl and use your back to help get the weight up, the bicep may not be strong enough to control the motion to lower your arm therefore damaging the bicep. I know this a little more technical than my usual articles, but over the years, I have learned that sometimes different instructors can mean the same thing but just have a different way of describing the method. Sometimes just that small difference creates an “ah-ha” moment of understanding. A more technical description may work for you.

Moral of the story: use good form and not momentum

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