(CS)^3: The First 3 Metabolic Pathways

We’ve all got Metabolic Engines baby!

Tyler getting a full extension burpee

Lets define metabolism:

Metabolism is the set of chemical reactions which enzymes in living organisms carry out to utilize energy and maintain life.

That sounds all good and dandy! It’s a pretty crazy system, maybe not 100% yet understood, however we have a good basis, and I’ll give a simple overview of the other 3 major ones that I didn’t cover last week. These are the Glycolitic, the Oxidative, and the Phosphagen. These round out the 4 major pathways (we looked at the lactate Citric Acid Cycle last week) I’m going to explain these all a little bit, and then how it relates to Crossfit and why we utilize them all so well in one program.

Glycolitic Pathway: Glycolysis

The glycolitic pathway was the first metabolic pathway that was studied, over 100 years ago by Louis Pasteur in 1860, Eduard Buchner in 1897, Arthur Harden in 1905, and furthermore was majorly defined by Otto Meyerhof in 1940. The original studies were done so using extracts of yeast where the yeast consumed glucose and converted it to carbon dioxide and ethanol. It was found that Glycolysis occurs in almost all living organisms, and because of that is considered the “mother of all” or archetype of metabolism.

This pathway involves taking a form of carbohydrate, in sugar form, and using a 10-step process (wait aren’t there a ton of ten-step processes? Yea but we didn’t make this one, it made us!) of intermediate steps, where different enzymes turn glucose into pyruvate. Each glucose molecule creates 2 molecules of pyruvate, and 2 molecules of ATP. In the intermediate steps other sugars like fructose (the sugars found in fruits) can enter the chain and be converted as well. Connect the dots with me and see that if you put a lot of simple sugars (like refined grains) into your body, it’s easy for the metabolism to create a lot of energy quickly. Due to survival instincts, if we have extra energy we don’t need, it is stored as fat. This is why eating vegetables as a carbohydrate source is better for insulin levels, because the carbohydrates in vegetables need to be broken down by other enzymes into more simple sugars before it can even enter this stage, and the energy will be utilized over a longer period of time as we aren’t as active (like how I’m sitting at my desk right now).

This pathway does not utilize oxygen molecules classifying it as anaerobic, and it is a relatively quick process because of this, and it dominates the 30 second to 5 minute range of power output (think 30 seconds of fast air squats).

The Oxidative Pathway: Also known as Cellular Respiration

This pathway is a much slower, but higher yield energy pathway. The suppliers are generally glucose, amino acids, and fatty acids. These sources are combined with oxygen to create ATP, carbon dioxide, and water. Whoa, now it makes sense why we breath in oxygen and breath out carbon dioxide. I know it’s cool I just blew your mind! Ok back to the explanation. These sources are converted to ATP through the electron transport chain, and when all is said and done: you get about 30 molecules of ATP from one molecule of glucose. This is 15 times as much as from Glycolysis! This pathway dominates things like longer distance running (anywhere from 5 minutes to 8 hours), where you can continue to put oxygen into your body. You can only breathe so fast, and without more oxygen, this process can’t go on, so when you’re doing a crap load of pull-ups or clean and jerks, and it’s much harder to take in large breaths consistently, this metabolic pathway can’t keep up.

The Phosphagen Pathway: Mucho Power Muy Rapidamente

This last pathway is also an anaerobic, which again doesn’t require oxygen. The main storage that I know of that is utilized is a molecule called phosphocreatine. In the bodybuilder world, and to a lesser degree the Crossfit world, Creatine is used as a sports supplement to increase strength and power in muscles, however it is present in high density in red meats, in lower density in other meats and eggs, and also created by the body naturally. Phosphocreatine is stored in the muscles and is a molecule which serves as an energy source which is rapidly mobilized to donate a phosphate to form ATP. The muscles have a very limited store of this however, and although it can be refilled within a couple of minutes of rest, it is depleted quickly, usually within 10-15 seconds of maximum effort work. This is the main pathway which gives us the EXTREME boost of energy to do things like a 1 rep max back squat, dead lift, or push press.

So those are the 3- I’m posting two charts here which may help a better of understanding of how they work.

Percentage of Power being supplied at a certain time

This first one is percentage of total energy in a given time domain, so if you look at time 60 seconds, this means that any exercise or power output that a person could sustain for 60 seconds will require about 65% of it’s energy from Glycolitic pathway, and the other 35% from the oxidative pathway. As apposed to a 1 rep max back squat that lasts 4 seconds, virtually 100% of the energy comes from the blue Phosphagen pathway.

Percentage of Total Power Metabolic Pathway is able to produce

The second graph represents a variation of the first, except here it shows what percentages of energy each pathway is able to sustain. This is a logarithmic scale thus the weird looking curves, and it is only a sketch to give an idea of how they work.

In Crossfit, since we do this type of “no-rest, next movement please, hell yes I want to go faster” workouts, we end up taxing all of these systems at the same time. When you do something like Helen: with KB swings, pullups, and running, the Phosphagen and Glycolitic pathways are dominating the KB swings and pullups, and then the Glycolitic pathway and oxidative are coming into play dominantly during the running. However, remember even during things like kettlebell swings and pullups, the oxidative pathway is still full steam ahead trying it’s damn hardest to provide as much energy as possible, because we’re taxing the other two so hard. That is why with interval training people have had great success doing long distance events. This same system does not work the other way however, if all you do is run long distance, your Phosphagen pathway will never get worked, and never become stronger. Crossfit works once again, nuff said, and there is science to back it up.

Cheers all enjoy your Friday. And Tax your metabolic pathways!

WOD 2/12/2010

A. Muscle Up Max Rep x 3
If you do not have a muscle up, work on muscle up progression. Must complete in 15 minutes.

B. 3 Min on 1 Minute off 5 Rounds
2 Muscle Ups
4 Handstand Push-Ups
6 Deadlifts
*Pick up where you left off on each round. Keep track of total rounds.

C. Optional:
Swim, Bike, Run, C2
5 Min on, 2:30 Min off, 6 Min on, 3 Min off, 7 Min on, Done.
All out max effort for total distance