Monday 12.17.13

Dec 17th, 2013

Category: CDR Community

Monday 12.17.13

Energy Systems Part 1:

Phosphagen Pathway

During a CrossFit Level 1 certification, trainers discuss the importance of the three metabolic pathways used during exercise: phosphagen, glycolytic, and oxidative. A CDR member asked me to break down these systems and further explain their importance and function during exercise. I know that for a lot of you, words like ATP, ADP, and phosphate might seem forgien or bring back painful memories of organic chemistry, so I’ll try my best to make it simple and get you all excited about the field of bioenergetics!

First of all, let me explain the word ATP. This stands for adenosine tri-phosphate, where one adenosine molecule is bonded to three phosphate molecules. Each phosphate bond stores approximately 11,000 calories per mole of ATP (one mole is equal is 6.02 X 10 molecules). So every time a phosphate group is released from ATP, large amounts of energy are released and ready to use for activity. This is why being able to generate large amounts of ATP during exercise is crucial for athletic performance.

The first pathway used in exercise is called the phosphagen system. This pathway supports very intense exercise lasting for only a few seconds, and would be used for activities like a one rep max snatch, backsquat, or  muscle up. This pathway relies on the reaction between a phosphocreatine molecule (PC)  and an ADP molecule (adenosine di-phosphate), which is then activated upon by creating kinase to produce one molecule of ATP and one molecule of creatine. This ATP then goes into our muscle fibers, and results in the contractions of our muscles during exercise. However, our muscles can only store a limited amount of phosphocreatine (about 3%), and so ATP generated by PC is limited. Once this PC runs out, our body then relies on additional ATP generation, which occurs in our recovery process. This regeneration will the depend on the conditioning and training of the athlete.

So what does this mean to me as a crossfitter? Well the phosphagen system is part of our anaerobic pathways, meaning that it does not require oxygen to form ATP. Anareobic systems build muscle, whereas aerobic systems burn muscle. Imagine the bodies of a sprinter and a long distance runner and their differences in muscle mass. Clearly the sprinter has more muscle than an endurance athlete, and that is because high amounts of endurance can be detrimental to muscle building and maintenance. However, performing intense exercise within short intervals will actually help with endurance by increasing your power and levels of aerobic fitness without muscle wasting. So by doing CrossFit, you will actually be building up your aerobic capacity for long distance exercises. When focusing on the utilization of your phosphagen system, you should rest about 2 to 5 minutes between sets. So let’s say if you were performing heavy back squats, you would optimally want to rest 2-5 minutes in between sets in order to maximize ATP regeneration during your rest period. However, I want you all to think of these 3 pathways as lying on a continuum, where our body transitions from one system to the next seamlessly. So once your activity lasts longer than a few seconds, the second pathway comes into play: glycolytic, which I will talk about next time.

Workout of the Day


10 Cleansters #115/75 (Adv=135/95)

400 m Run

10/6 MU or Wall Climbs

400 m Run



If you haven’t brought in your Adopt-A-Family gift yet, we are not going to deliver them until Wednesday, so you all have until Tuesday or early Wednesday morning to bring them to the box!

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