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Energy System Training – Part 1 – Energy production

Posted 20th October 2015 by Josh Schouten

The CrossFit Hackney training ethos rolls on as we move into the final phase for 2015.  After spending 16 weeks building Juggernaut strength, 16week focusing on speed and power with Olympic lifts and Russian squats, we will now move to Conjugate strength and energy system training (EST).

What do you know about EST?  Do you understand the difference between aerobic, anaerobic, immediate energy metabolism, lactic and alactic training?  Understanding the basics of human energy production can be helpful in understanding fatigue and how different training principles can be used to maximize it.  Energy production is critical to human survival and our body is continually regulating the process to make sure energy demands are met through homeostasis.

Various internal and external stressors can impact our body’s ability to produce energy. Temperature, blood pH levels, blood pressure, hydration, and blood sugar levels can all impact energy production.

The body uses two primary energy pathways:

Anaerobic – without oxygen

Aerobic – with oxygen


The Scientific Talk

The number one thing to remember is that EVERY cell in our bodies – muscle cells, brain cells, heart and lung cells, etc. – need energy to survive.  Exercise conditioning is directly related to energy production and expenditure.  This energy comes from a molecule called Adenosine Triphosphate, (ATP).   Every muscle contraction requires ATP, and the result of muscle contraction produces a byproduct Adenosine Diphosphate (ADP).  When ADP is coupled with Creatine Phosphate (PCr) it can regenerate ATP, basically a way to produce energy without the demand for oxygen (anaerobic).  This cycle continues until PCr stores in the muscles are depleted (10-12-seconds).

[ADP + CP = ATP]

The glycolysis energy pathway takes lead on the production of ATPs between 10-seconds and 2-minutes of work.  Glycolysis uses glucose (C6H12O6) as the main fuel to produce ATP.

Exercising for longer period of time requires the complete oxidation of carbohydrates (CHO) or free fatty acids.  Typically our CHO store can last for approximately 90-minutes and the free fatty acids stores can last for several days.

The Non-Scientific Talk

We can think of our bodies like a hybrid car which can run on electricity or petrol power.  The aim of a hybrid car is to improve energy efficiency by using battery power before burning petrol.   The hybrid car has the ability to recharge the batteries as it is working, or when it is stationary and the petrol engine is running.

At the onset of activity, our muscles predominantly use the local battery store of energy to do work. As they are doing work they recycle the energy for as long as possible (10-12-seconds).  Once the local power source is depleted the muscles need to start calling upon the alternative petrol source.  When resting our bodies can slowly recharge the batteries.  At some point in time the petrol tanks will need to be refilled if muscles are going to continue to work.

In the next post we will talk more about energy production and energy expenditure.