Energy Systems – What Are They? Why Do I Care?

Have you ever thought about what are you trying to gain by doing the workout that you are doing?  Each of the workouts that we program have a specific intent, which differs based on the time, weights, and movements in the workout.  The intents of each of the workouts will play into different energy systems.  What are energy systems?  Glad you asked.

The energy for physical activity comes from the conversion of ATP (adenosine triphosphate) to ADP (adenosine diphosphate).  The human body has 3 main energy systems that are used to produce ATP for muscular activity.  These are the Phosphagen, Glycolysis, and Oxadative systems.  Don’t worry, we don’t expect you to memorize these terms, but we do want you to be aware of what they are and what they do.

Phosphagen – Think of this as the short-term, high intensity system.  The phosphagen system is an anaerobic process where muscle cells must rely on other reactions that do not require oxygen to fuel muscle contraction.  Some examples of this would be sprints or 1 rep max lifts.

Glycolysis – The is the medium intensity system.  Glycolysis is the breakdown of carbohydrates (glucose), stored in the muscles or delivered your blood to create ATP.  Glycolysis doesn’t depend on oxygen, but can use oxygen if it is available in the blood.  Activities in the Glycolysis system are in the 30 second to 2 minute time-frame.

Oxadative – You probably guessed it.  The oxadative system is the longer, low intensity system.  The oxadative system is an aerobic (exercise that improves or is intended to improve the efficiency of the body’s cardiovascular system) system that uses carbohydrates and fats to create ATP.  Examples of the oxadative system would be a long bicycle ride or long run.

That all sounds great, but why do I care?  When you are training in CrossFit, you are training in all of the energy systems.  Sometimes in the same day.  You may start with low rep strength movements, move to a quick workout, and then end with a nice long cool down on the rower.  In order to continue to grow as an athlete, you want to train in each of these systems.  Specific workouts are designed to hit specific systems and this is one of the reasons why we recommend that you “scale appropriately”.  Just because you can complete the workout with the correct weights or movements, doesn’t mean that you are training in the system it was designed for.  Doing Fran in 3 minutes is much different than doing Fran in 15 minutes and work two different energy systems.  Before you start each workout, think of what system this was designed for.  If you aren’t sure, just ask the coach how many rounds you should get, or what time range you should be in.  If you are always the last one to finish, or find yourself way behind on reps/rounds, take it as a sign that you should be scaling.  Remember to check your ego at the door and it’s not always about doing a workout RX.