WHAT ACTUALLY CAUSES MUSCLE GROWTH?

By Mike Koehler

By now we all know that CrossFit helps athletes all over the world build muscle and change their body composition for the better.  But what exactly are the mechanisms that encourage muscle growth?  What’s going on in these WODs that brings about changes?  Below are five things that you will find sprinkled throughout NOVA’s CrossFit WODs that stimulate muscle growth.

First, we’ve got “Progressive Force Overload”.  In simplest terms, this is pushing or pulling more weight in your current workout than you did in earlier workouts.  Let’s say you accomplished 5 sets of 5X shoulder presses last week at 95, 105, 115, 115 and 115 lbs.  If that workout comes around again this week, you could increase the weight on those last two sets to say 120 lbs.  That’s a progressive force overload which is very likely to cause your body to start making changes to keep up with the demand.  Force Overload is the obvious first step in strength building, but there are times when the body hits a plateau, so we still need other training styles to keep ourselves advancing.  

Second, we’ve got “Progressive Increase of Repetitions”.  Let’s say last month you did 3 sets of ring-rows during a workout:  12 reps, 10 reps, 9 reps.  This month if that workout comes around again, you might push yourself to get 12 reps on all three sets.  That would be a progressive increase in your reps.  This is one way you might break through a plateau in your weight capacity, and it’s the primary mode of increasing capacity in any strictly bodyweight exercise.  One has to be careful with this kind of training modality however as an ever increasing rep count can lead to soft tissue strains, etc.  That’s why we keep changing things up.

Third, we’ve got “Metabolic Conditioning” (or what I like to think of as Progressive Chemical Overload).  This is one area where CrossFit typically puts other fitness regimens to shame.  The MetCons we do start your muscles burning, and do we stop there?  Heck NO!  We push on until the RFT or AMRAP is complete.  This keeps your muscles in a chemically overloaded state, and your body starts adapting to meet this new demand to sustain higher and higher power output levels.  Let’s stop to think on this:  the weight may not have gone up, and the reps may not have gone up, but by pushing ourselves to continue at a steady pace with little to no breaks we cause muscle adaptations anyway!  BOOM! (visualize mic drop here).

Our fourth category is “Eccentric Force Application”.  This is what’s often thought of as the “negative” part of a repetition, such as lowering yourself down at the start of a squat.  The application of muscle force while the fibers are being elongated stimulates muscle growth.  This is why some WODs call for something like a 4 count while lowering the weight and then a normal speed to raise the weight.  Theories on why this works are that:  1) the stretching of the fiber under load causes more micro-tearing, and 2) blood can flood into the muscle fibers more readily in this training mode.  Another common example of eccentric loading is catching the med ball during wall-balls and lowering yourself down to femur-parallel.  Contrast this with box jumps where we stop at the top of the movement and step down – very little eccentric component.  You may notice a significantly higher level of muscle soreness after eccentric load training, so while it’s very effective we don’t want to do this kind of workout every time.  

The fifth category is “Plyometric Training” – i.e., explosiveness.  When the muscle is called upon to apply force very rapidly it recruits different muscle fibers (Type II or “fast-twitch” fibers).  Exercises that have a plyometric component include barbell cleans, snatches, kipping chest-to-bar pullups, box jumps, push-presses, and kipping handstand push-ups.  In addition to recruiting different muscle fibers, the explosive acceleration of the weight causes additional forces above the gravity force.  This in turn spurs muscle growth.  Keep this in mind if you are ever traveling and have to work out with only light weights:  being explosive is one way to increase the difficulty without increasing the weight.

We encourage everyone to become a more astute athlete and to look for these different training modalities in the WODs.  

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