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Isometrics:  What it is and ways to incorporate and why?

By now, we should all be pretty well versed in the 3 muscle actions: concentric, eccentric and isometric.  I want to focus on ISO’s this month and dive into a bit of the physiology and ways to incorporate them depending on the goals of a client.

Isometric refers to the muscle producing force without movement, simple as that. We can accomplish this via yielding isometrics and overcoming isometrics; the intent is different in both versions, but the external result is the same.  

(There are also sub types of isometrics, but all essentially fall into one of the two categories mentioned below.)

Overcoming isometrics refer to moving an object that cannot be moved, think mid thigh pull against the pins, these tend to be more neurologically demanding and have a greater transfer towards concentric strength. These are typically performed for very short and intense efforts (no more than 12 seconds typically) and have a greater impact on strength as opposed to muscle size. 

To perform a yielding isometric, think of holding a position and not letting the weight or form drop.  These movements will transfer more to eccentric strength and are not nearly as neurologically demanding as overcoming isometrics.  For that reason you can usually perform longer efforts more frequently and will increase muscle size more than strength.  These are also great for reinforcing the mind-muscle connection in a movement, and in my opinion, the best way to clean up a poor movement pattern.  As coach Lee Boyce mentioned in a post last week, (I’m paraphrasing), “If you want to truly demonstrate how proficient of a lifter you are, don’t show me how quickly you can move a weight, show me how slowly you can execute a set.  It takes real strength and fine tuning to be able to control weight on both sides of the rep.

I’ll wrap this up with these final 4 points on using isometric movements for strength, since that’s what we all want to know anyway.

  1.  You can recruit up to 10% more muscle fibers during a maximal isometric than during a maximal eccentric or concentric muscle action.  Fiber recruitment is one of the crucial neurological factors affecting strength, meaning isometric recruitment can train the nervous system to be more efficient at doing so.
  2. The firing rate of recruited muscle fibers is higher than during maximal eccentric muscle actions and potentially higher than during concentric muscle actions. Over time, this means the body can be trained to produce higher firing rates during all types of muscle actions, which is another way to increase strength production.
  3. Focusing strength training at certain joint angles.  We can perform isometric holds at the weakest points of a lift (typically mid range or any other sticking point during a movement), allowing us to focus and build strength where it is needed most.
  4. Functional isometrics (Christian Thibaudeau talks about these a lot) are using very short range, partial lifts to help reduce reciprocal inhibition, basically over time, desentizing the body/nervous system to reduce its protective mechanisms in order to use more of your strength potential.

In our programs at Nakoa, you’ll notice a lot of intra set and iso dynamic loading for our clients, hopefully you can now truly see the benefit and the why that is used and when during a program.  This was just a quick rundown on the isometric muscle action, we can obviously dive way deeper into the physiology and other subtypes, so let’s see what questions and discussions this can prompt.  Looking forward to your feedback!

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