When most people think about becoming stronger, the only variable often looked at is the weight on the bar, or the size of the dumbbell. After all, if you're squatting 225x5 on week 1, then 250x5 on week 3, you've gotten stronger, right? Of course...it's progressive overload at it's finest. However, what happens when adding weight to the bar simply doesn't cut it? If you bench press 200lbs for six reps one week, and then are unable to bench 200lbs for seven reps the following week....you've failed to get stronger, correct?

Not necessarily. In fact, your strength gains may have significantly increased, but you failed to realize it, and thus the fuming and fussing on the car ride home begins.

First, let me provide some video footage of my wife, Kelsey, hitting an impressive weighted chinup personal record. Here she is, on Thanksgiving morning, pulling her sternum to the bar with 45lbs dangling from her waist:

(Yes, women can do pullups. Boys, you have some work to do.)

For the longest time, Kelsey was stuck at +20lbs strapped to her waist. She couldn't seem to break that barrier. Then, in the course of only a few months, she added another 25lbs to her waist! How did she do this, you inquire? Whew, I thought you'd never ask....

She stopped grinding out her reps.

You know....the kind where you kick your feet around, pulling yourself up - or pressing the bar - slower than molasses running uphill in July.

Up until her recent training cycle (the one where she hit the chinup PR), she ALWAYS grinded out her reps. In her mind, if she wasn't adding more weight to her waist, then she wasn't getting stronger (she will admit this, too). This continued for months on end, her max chinup remaining right at a stubborn +20lbs. However, once she stopped worrying about the weight, and kept her reps clean and crisp, her chinup strength skyrocketed! She of course did this in conjunction with some intelligent programming, but that's not what I'm going to get into here.

The same thing can happen to you, whether it's your bench press, squat, deadlift, overhead press, or whatever. And you can thank Newton's Second Law for this phenomenon. For those of you who may forget high school physics, and/or are more visual learners, let me provide you a picture:

Looking at the equation, and using a bit of Algebra 1, it's easy to see that there are a few ways to increase F: one of these being increasing m while keeping a constant; the other being, increasing a while keeping m constant. If you don't know what F, m, and a stand for, then shame on you. I'll wait while you look it up.

I'm about to get my nerdification on a bit, so if you're uninterested in reading further, take home this: you can still get stronger by moving the same weight FASTER, rather than needing to add more weight to the bar. In fact, this is often the limiting factor in one's inability to continue to improve his or her strength.

Okay, for those of you that are still with me, we know that there are three primary factors that affect the phenotypic properties of muscle:

The Nervous System
Mechanical Loading
The Endocrine System

The nervous system is the driving force behind adaptation of our motor units (a motor unit being a motor neuron and all the muscle fibers it innervates). In fact, it is the nervous system that's responsible for determining whether your fibers are fast twitch or slow twitch.

Mechanical loading refers to moving a weight (as in a squat or bench press), and the endocrine system would be all those hormones running throughout your body.

Today, we're going to briefly glimpse at the first two on the list.

With the F=ma equation, the "F" would be the force your muscles produce, m would be the weight on the bar (or the mechanical loading), and a would be how fast you move it.

With regards to muscle fiber strength and size changes, a propelling force in inciting these desired adaptations is neural drive. The more neural drive you have to the muscle fibers, the more they develop in size and strength. Essentially, you're tapping into your high threshold motor units, the one's that have the greatest potential for size and strength.

What is one way to increase neural drive? Increase force production.You know, that big F in the equation.

Since we can't perpetually increase F by adding weight on the bar (if only, if only....), we can still cause F to go up by improving our a, the acceleration!

More acceleration = more force output = more neural drive to the muscles = more chances of the opposite sex wanting to hang out with you. Yes, that is scientific fact.

All this boils down to is that you need to measure improvement not only by the weight the bar, but also by how fast you move it.

If I could call out one of the greatest mistakes I see in the average gym goer, it is that they are constantly grinding out reps in their attempts to get their sexification on. And, even worse, they'll hit failure, missing reps and crashing the bar onto the safety pins. This will only fry your nervous system and make you weak. The strongest lifters in the world never miss reps. I think they must be on to something, no?

Stealing an example from Roger Lawson, continuing to grind out your reps (i.e. moving the bar slowww and coming close to failure) is akin to continually punching the accelerator and slamming the brakes at each traffic light. You know, like that hilarious scene from Meet the Parents.

If your body is the analogous to the car, and your nervous system is comparable to the engine, what do you think will happen to your performance in and out of the gym? Not positive things, that's for sure.

Going back to Kelsey's example, she spent a solid few months staying far away from failure, ensuring that her reps were always clean and crisp. By improving her acceleration, she was enhancing her nervous system via improved force production, staying fresh by avoiding slow reps, and eventually added 25lbs to her chinup. Easy peasy.