Why Physics Matters In Training

Why Physics Matters In Training


I hesitate to even delve into this topic for fear that mere mention of physics might trigger PTSD in some readers...

Flashbacks to indecipherable equations and destroyed GPAs notwithstanding, the gym is probably the ONLY place in the real world that all of that studying actually pays off for your average Joe. 

And luckily, we're not dealing with quantum theory or thermodynamics here. Really the most crucial concept that we're concerned with when it comes to improving training is that of mechanics—specifically, levers. 

At the base, our musculoskeletal system's interactions are really just a bunch levers being acted on by opposite forces.

We have our muscles on one side, the external load on the other, and stuck in the middle of this power struggle are our bones that act as intermediaries of force transfer. 

Anyone who has taken an introductory physics class (or even stopped to think about how things work for a second) will note that, outside of the tension of the muscles and the weight of the external resistance, one other variable plays a massive role in how this equation is balanced—the length of the moment arm. 

A moment arm is a way for us to understand the relationship between force and distance. 

It might be more easily understood as an example: let's say we are performing biceps curls. Our biceps tendon attaches just below our elbow on the upper forearm which is what allows for elbow flexion when the biceps shortens. And when we're holding a DB in our hand during curls, we can think of the moment arm as being equal to 1.

But what were to happen if, instead of a DB, we used a novel contraption that held a weight x inches beyond our hand? Now the moment arm would be 1+x and the tension that our biceps would have to generate to shorten would be much greater due to the longer lever length. 

And what about the opposite? What if we used a device that allowed us to place a weight on our forearm at y inches above our hand? Well, now the moment arm would be 1-y and we would be able to curl it with much less force output!

In reality, this is a massive bastardization of the math, but hopefully the point was more easily understood. 

A larger moment arm means we will have to work harder to move a load. And a shorter moment arm means that a once hard task becomes much more trivial! 

Ok but how does this apply to training and how can we use it to our advantage?

The application is thankfully MUCH simpler to explain and grasp than the underlying principles. 

Let's use the Lateral Raise as an example:

Holding DBs in our hands, it's pretty noticeable how much more challenging it is to lift them when we have our elbows locked out versus if we allow for a bit of bending. The very reason why you rarely ever see laterals performed with perfectly straight arms is precisely because it will quickly bruise the ego. Taken a bit further, the point becomes more apparent when comparing locked elbows with 90º flexion. The difference is VAST to say the least. 

We can see this same foundational truth pop up again and again with many variations across pretty much every body part and muscle group...

Straightening the elbows turns a DB Press into a DB Flye—All that is required is extending the moment arm. 

Adjusting the pad on Machine Hamstring Curls so it sits further down the ankles versus up on the calves will make the movement much harder. 

Keeping the bar close to your shins when performing Stiff Leg Deadlifts will allow you to use more weight than if you let it swing away from you. 

Though these are widely variable examples with completely divergent applications, the one thing that will never change is the physics of biomechanics. Take the time to understand it and you'll begin to see training like you've never seen it before. 

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