No matter what you do for a living, there typically comes a “eureka!” moment when things become ever so clearer and, as a result, you become much better at whatever it is you do. As a personal trainer, that moment came me for when I learned the important role physics plays in resistance training.

Resistance training, broken down to its lowest common denominator, is nothing more than a battle between two opposing forces: resistance force and muscular force. As you move a resisted object (i.e., dumbbell, bar, cable, elastic band, etc.), the force your muscles generate are either greater or weaker than the opposing resistance force depending on what direction you are moving. Understanding and knowing how to control these forces will help you get the most from your resistance workouts. To better illustrate this point, I’ll use two exercises as an example: barbell chest press and barbell biceps curl.

Barbell Chest Press

Like almost every other resistance exercise, the chest press is comprised of two basic motions: 1. lowering the bar down to your chest, and 2. pressing the bar up to the starting position. As you lower the bar, your chest muscles must reduce their force output to allow the bar to move downward. This is called the “negative” phase of the movement – the resistance force is greater than the muscular force. Once the bar is as low as you want to get it, your chest muscles must now increase their force output in order to move the bar upwards. This is known as the “positive” phase of the movement- the muscular force is greater than the resistance force.

Barbell Biceps Curl

The two basic motions for this exercise are 1. bending at the elbow joint to raise the bar, and 2. un-bending at the elbow joint to lower the bar. As you bend your elbow to raise the bar, your biceps muscles must increase their force output in order raise the bar – the muscular force is greater than the resistance force. As you un-bend at the elbow joint, your biceps muscles must decrease their force output in order to lower the bar- the resistance force is greater than the muscular force.

Now we all know that in order to build muscle, you must tear existing muscle fibers by overloading them (this is the main purpose of resistance training).When the resistance force is greater than the muscular force, you stand the BEST chance of tearing muscle fibers. Why? Because the muscle is at a disadvantage! It is losing the battle between the two opposing forces.

Often, we neglect the negative phase of a movement -- focusing more on the positive and simply allowing momentum or gravity to take over the negative. I submit that doing so creates a HUGE missed opportunity to tear muscle fiber and thus slows the muscle development process. Focusing on the negative phase of a movement allows you to make the most of your workout and after all, isn’t what we all aim to do in the gym?

Jeff Mendoza is a certified and insured personal trainer with over 13 years experience helping others achieve their individual health and fitness goals through developing and administering cutting edge, exciting and effective one-on-one training programs. For more information, check out http://chizeled.net

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