Meathead Physics

Sometimes I see some guys talking about lifting weights like it’s quantum mechanics. You don’t need to be a rocket scientist to get strong. With that said, understanding some physics will make you a better lifter. That makes me sound smart, doesn’t it? Good. That’s the only reason I’m doing this.

What I didn’t tell you is that the physics you need to know is about the third-grade level. So as long as you’ve graduated from third grade, you can probably be a good lifter. (That still makes me sound smart to second graders.)

Here’s what you need to know:

The three laws of motion, or force.

Moments and moment arms.

These are basic, elementary school concepts. Literally.

I’m going to review each one, so the next time someone asks you for advice on lifting, you can say, “Well, you need to understand some basic physics first.”

What is strength?

Strength is your ability to resist and overcome force. So it will help you to understand how force actually works. Because if you don’t, you’re dumber than a third-grader and have bigger problems than a lack of strength.

Newton’s Laws of Motion (for meatheads)

There are three things you need to understand about force if you want to overcome it.

Every object in a state of uniform motion will remain in that state of motion unless an external force acts on it.

Translation: A barbell won’t move until you move it.

Force equals mass times acceleration.

Translation: Mass is the dumbbell/barbell/kettlebell/etc. Acceleration is gravity. So a 60lb dumbbell is heavier than a 20lb dumbbell because it has more mass and therefore, needs more force to lift it.

For every action, there is an equal and opposite reaction.

Translation: To lift a weight, for example, a barbell on your back, the upward force you’re creating needs be greater than the downward force of the barbell. If they are the same, the bar won’t move. If the barbell has more force than you can create, you’ll get smushed.

To understand how to best apply these laws to the bar, let’s go over moments and moment arms.

Moments and Moment Arms

The shortest distance between two points is a straight line. The shorter the distance, the less work you’re doing to get there. That’s why we lift in a straight line whenever possible.

The simplest explanation of moments and moment arms is to imagine unscrewing a bolt. The moment is the turning force (or torque) applied where the wrench fits the bolt. The moment arm is the distance between the moment and the point of force (where your hand presses the wrench). For a wrench to work, it has to withstand torque at the bolt, and the force applied along the moment arm. This way, the full force of your hand pressing the wrench will transfer to the bolt.

This would be great info if this article was called "How to Use a Wrench," but how does this play out in exercise?

To transfer the force you create with your muscles to lift a barbell, the moment arm must stay rigid. Since our bodies are a bunch of weird, floppy limbs and joints, it's not enough for the moment arm to stay rigid: The entire body needs tension. Instability anywhere from your feet to the bar means that force isn’t transferring efficiently. 

Imagine unscrewing a bolt with a wrench, and the handle of the wrench became a noodle. You'd lose your leverage, and it would be much harder to loosen the bolt. On the plus side, you have a noodle. In other words, there can be no noodles in your body when lifting a weight. For more details on de-noodling yourself, check out the bracing guide. 

As you can see, these are pretty easy concepts. But they take a lot of practice to master. Your body is not a machine that is built to lift weights, so you have to teach it how. For more on this, check out the squat guide, the deadlift guide, or the bench press guide.