CrossFit founder, Greg Glassman, published his now infamous “What is Fitness” article in the CrossFit Journal back in October of 2002. If you have never read it, please do.
In this publication, he discussed the importance of training the three most prevalent of our body’s energy pathways: Phosphagen, Glycolytic and Oxidative for the purpose of overall fitness. I want to preface this by saying that I’m not a biochemist, but it is a very worthwhile discussion. So, let’s go for it anyway and please don’t crucify me in my attempt to regurgitate science.
Energy is moved through the body and towards the end use (muscle groups in this case) by means of ATP (Adenosine triphosphate). If ATP is the vehicle, these three pathways are the highways, if you will, to get them there. It seems to me that there is a pretty overlying misconception in CrossFit that we only run on one pathway at a time. From my experience and readings, that’s definitely not the case. We’re constantly running on all three, but one or two will be the primary contributors at a given moment.
The first, Phosphagen (phosphocreatine or PCR) delivers energy in activities that last only a few seconds. This is for the highest powered activities such as 100m sprints, heavy lifts, and max height box jumps.
The second, Glycolytic (or anaerobic) is the pathway which is used for intense activities up to several minutes at medium-to-high power outputs. Oxygen is not used as an energy source here as we are burning through glycogen stores in the muscle groups themselves. A great example of this would be “Tabata” sets.
The third, Oxidative (or aerobic) is for anything lasting over a few minutes and generally for low-powered activities. In this pathway, oxygen is the primary source of energy via fat metabolism (fatty acids). Besides lifting and sprint interval days here at CPC, you’ll find yourself utilizing this pathway in the large majority of our workouts once the first two are depleted. If while you read this, you’re starting to think that you want to be “skinny” so the best thing to do is stay in the oxidative pathway for extended periods of time, please think again. Check your nutrition instead.
So, what does all this mean from a programming standpoint for CrossFit? We have to hit all 3 pathways on a fairly regular basis in our quest for “elite fitness.” Most programs you run into will train nothing but the third pathway (oxidative) due to a relatively low level of intensity. In contrary, many weightlifters may never touch the oxidative pathway. For a good percentage of our workouts, we’ll hit all three in under 5 minutes.
For example, in our famous friend Fran, the intensity is so high (close to 100%) that we will most likely deplete the first two pathways in under two minutes and then rely on the third to pull us through to the finish line. In something like the Filthy Fifty, which is a longer workout lasting 15:00+, we may pace ourselves (70-80%) a bit more so it may take up to 4-8 minutes to deplete the PCR and glycogen stores in our muscles then switching to the third pathway around the 9:00 mark. A great visual indicator of an athlete’s transfer from glycolytic to oxidative is increased respiratory rate.
Another disclaimer: There’s vast amounts of variables that go into how each individual uses each metabolic pathway including fitness levels, relative and absolute intensity, muscle mass (stored PCR and glycogen), etc.
So am I saying CrossFit is the best and most complete fitness program out there? Not if you’re solely sport specific. Am I saying that it’s the best fitness program out there for people looking for general physical preparedness (GPP)? Maybe. Am saying this is the only way you should train if GPP’s your ultimate goal? It’s certainly effective. Has it changed my life? In more ways then you could imagine. No matter what, I believe you should do what you love. Maybe CrossFit becomes that thing you love or it makes that thing you love that much better.
Whatever the case is, you should ask yourself the following questions; if the zombie apocalypse happened today, would I be able to:
- hurl a 45 pound rock at an approaching zombie’s head?
- out sprint a zombie dog and hurdle a cyclone fence?
- outrun a pack of zombies limping/running at a 10:00 pace to the next inhabited safe zone approximately five miles away (as the crow flies)?
That, my friends, is why I train.
Today’s Workout:
Reverse Tabata L-Sits
Then:
In 2o minutes perform as many rounds as possible. If you miss a round, sit out the minute and start fresh on the next one. Your score is the total number of rounds that you complete in 20 Min of:
Every minute on the minute perform – 8 Burpee Box Jumps (24″/20″)
