Part 1

When talking about any human movement, there are three main muscular actions that are at play: Eccentric, Concentric, and Isometric.  Each one of these actions are independent from the other and all play a role in how we naturally move.  In this article, I am going to dive into each of these muscular actions, because many of the topics I will be writing about on the ECF website will utilize these terms. It is important to remember that not everyone has a clear understanding of terms that we use often in our training, and that is one of the main reasons Josh, Jess, and I are breaking things down and sharing our knowledge with our ECF Community. What is the point of writing articles that discuss in-depth movements, concepts, and terms that the reader doesn’t quite understand? We want you to get the most of the information we provide you, so I wanted to start from the basics…. So here we go!

(Picture Credit: Jim's Primal Suit-

Eccentric Phase

Some say the eccentric phase is the most important of the three phases, which would not be wrong.  During the eccentric phase, your muscle is lengthening or stretching.  For example, during a barbell bicep curl, descending or bringing the barbell down would be the eccentric phase because the biceps are stretching and lengthening.  This is very important because this phase is where we can become “sore”.  Let me say that again, the eccentric portion of the lift is where soreness comes from! Soreness is a great thing.  This means that the muscle tissue is breaking down, which needs to happen in order to build it back up.  During that build up, we become stronger. Therefore, the eccentric phase is also where our strength comes from!  Without good eccentric strength, bringing the barbell back up again after descending or bringing it down would be very difficult. So, please do not be “that person” in your gym that looks like they are rabbit humping a bicep curl.  Take some weight off, control the ECCENTRIC portion of the lift down, and explode the weight back up.  Remember this... the more you can control the movement on the way down, the more you will be able gain when you bring it back up.  As that muscle is lengthening we are storing energy.  We want that.  It is a powerful thing.  


The concentric phase of a movement is going to be the opposite of the eccentric phase, so this phase is going to be the shortening, or contracting, of a muscle.  Again, this is still a very important part of a movement, but very different from what you see during the eccentric phase.  This is where blood flow and recovery happen.  The more blood that can be pumped into a muscle, the better it aides in recovery.  Blood is the biggest transporter in our bodies.  So the more blood that is being pushed around... the better.  Think of “bodybuilding” style of training.  Have you ever heard your gym partner say, “Damn my arms are going to explode”?  Well this is a result that comes from the concentric part of the lift.  But remember... the concentric phase of the lift is only going to be as strong as the eccentric part of the lift.  Train them both with a plan and that is a recipe for success!!!


I am sure everyone has heard of an isometric exercise before, but I am willing to bet that you are thinking of it differently.  See, most people believe that an isometric action is just isolating a muscle group... which is not the full story.  An isometric action is a “stand still” of sorts,  meaning that an external force is equal to the internal force.  For example, the weight of your dumbbell in a dumbbell bicep curl would be the external force and the muscular force you are applying to that dumbbell would be internal force.  When both forces are equal we now have a “stand still” or a “pause” in the movement.  That is what we call an isometric action!  During a bench press, if I tell you to hold the bar at your chest for 2 seconds both forces are equal (isometric) until you apply enough force to drive the barbell back up again.  Isometric actions are a very powerful training tool that I could discuss in depth in it’s own article... but that is a topic for another time!

Now that I have given you a basic understanding of these three essential muscular phases and actions, we can start to dive into how they are programmed into your training. Make sure to stay tuned for Part 2 of this article: “Muscular Actions: How to Program Them into a Training Program”.