Proper Energy System Development in CrossFit and Other Sports

When I first began studying exercise science, I was introduced to Westside Barbell and EliteFTS which led me to common strength and conditioning resources like Supertraining, Science and Practice of Strength Training, Block Periodization and so on. I started training CrossFit a year ago and since then have been taking my previous education and experience and applying it to my new training goal. In this article, I am going to discuss the difference between building and testing, the three energy systems, and how to properly structure training to maximize development in each.

Building vs Testing

When it comes to training, there is a time for building and developing and there is a time for testing. In school, we study material throughout the week and then test that knowledge with a quiz. In football, we train and develop our football skills throughout the week, then we test those skills against an opponent on game day. When programming, there must be a clearly defined purpose for each training component; each day, exercise, set/rep scheme, load, etc has a specific purpose. That purpose is should be to either to develop a capacity or a skill. Development, or building, is different from testing in that is is done with the priority of improvement while testing is done with the priority of competition. This is very important for us to learn as CrossFitters. When the only goal is to “win the whiteboard” or hit PRs, then we are severely limiting our overall development. There is a reason that football players aren’t developed by playing a game every day and that we don’t just quiz and test kids in school. There are times in which we do need to test but those times need to be far less frequent than our developmental days. Developmental doesn’t mean easy, in fact it should be far from it, but it does mean that the focus is developing a capacity and/or a skill, not testing it.

Energy Systems Basics

There are three metabolic pathways through which our bodies can derive energy for muscular contraction. Between these three pathways, we are able to do things like perform a heavy back squat, row 500m, and run 3 miles. Here is a simple break down of the three energy systems:

Phosphagen (aka alactic): Efforts of maximum intensity of 10 seconds or less, examples: 1oo meter dash, heavy 1-3 rep squat

Glycolytic (aka lactic): Efforts of medium-high intensity up to 120 seconds, examples: 400 meter sprint, 500 meter row, 10-20 reps of most movements

Oxidative (aka aerobic): Efforts of low intensity greater than 120 seconds, examples: 2000 meter row, 3 mile run

Without going into too much detail, I want you to understand that each energy system has a certain time duration for which it is used for producing energy. Picture each energy system flowing from one to another over a line like the image shown below. On either side of each energy system we see the words power and capacity. Power refers to force output within that energy system and capacity refers to the ability to maintain output within that energy system. For example, lactic power would be the ability to produce maximum force within that energy system (like a 250m row as fast as possible) where as lactic capacity would be the ability to maintain output within that energy system (like a 400 m sprint). Power and capacity fall on either side of the time domain for each energy system. A 1 RM Squat would be alactic power while a 100 meter dash would be alactic capacity. A one mile sprint would be aerobic power while a 50 mile run would be aerobic capacity. Finally, the recovery time will also influence whether power or capacity is being developed. For example, when developing alactic power for the clean, full recovery would be necessary. This might look like 3×2@90% with full recovery (2-5 minutes between sets). However, if we are developing alactic capacity, then we would not want full recovery. This might look like 6×1@90% with a 60 sec break between each set. The volume and intensity are the same but by lowering the rest periods we do not allow full recovery to occur.





3 Types of Recovery

When we train, there are three areas in which our body will receive stress: neurological stress, tissue stress, energy substrate stress. The level of stress, fatigue, and recovery time will be different for each area for different types of training stimulus. For example, a heavy back squat is going to cause a large amount of neurological fatigue but a relatively small amount of tissue and energy substrate fatigue. Three sets of 10 reps on bench press with a 10 second negative on each rep would cause a very high amount of stress to the tissue, a medium amount of stress to energy substrates, and a small amount of neurological stress. A 10 mile run would be very demanding on energy substrates but cause only a very minimal amount of stress to the CNS and tissue (assuming the person is a trained runner). In the examples above under the energy system portion, we can see that by manipulating the recovery, we can target different training goals (power or capacity) within each energy system. In doing so, we are primarily manipulating the recovery of the CNS and energy substrates as tissue recovery takes much longer. It typically takes about 3 minutes for ATP to be replenished after a maximal alactic output. The lactic energy system is limited by the increase of lactate and hydrogen ions within our muscles during training. This is the burn we feel during intense periods of high output. This can take anywhere from 90 seconds to 3 minutes to clear from our muscles. Aerobic capacity from an energy substrate standpoint is only limited by the available energy stores (glycogen, fatty acids) within our body and/or our ability to continually replenish those stores through nutrition. To summarize, we must allow full energy substrate recovery to develop power where as allowing only partial recovery will help to develop capacity.

Tying It All Together

As stated above, the majority of our training days need to be developmental days in which we are trying to develop a specific skill or capacity. Skill refers to the technique/motor coordination of a movement while capacity refers to the output of that particular skill. For example, there is the skill of doing a snatch which is the ability to perform the movement with the proper technique and there is also the capacity of doing a snatch which could be anything from a snatch 1RM to a 95 lb snatch for max reps in 2 minutes. Each of these examples falls into a different energy system as stated above. Below, we can see under which stages of CNS fatigue different capacities should be trained:

Well Rested/Low Fatigue

  • Alactic Power
  • Alactic Capacity
  • New Skills (non developed motor patterns)

Low/Medium Fatigue

  • Lactic Power

Medium Fatigue

  • Lactic Capacity
  • Aerobic Power
  • Technique Perfection of developed motor patterns

High Fatigue

  • Aerobic Capacity
  • Flexibility/Mobility

When developing our training programs, we need to define our training goal. What skill and/or capacity are we trying to develop? If it’s a new skill, we need to train it in a state of low fatigue with full recovery. If it’s a skill we already possess, we need to decide which energy system we our trying to develop that skill in and whether or not we want to develop its power or capacity within that energy system. Next, we need to manipulate the training program to properly address the CNS and energy substrate recovery necessary to reach our training target. We can use the CNS chart above and our knowledge about the time domains for energy systems and energy substrate replenishment to correctly program.

Final Note

Intensity is relative. If a workout has 20 reps of 95 lb thrusters for time, the person with a 135 lb thruster max is going to be working in an entirely different energy system than the person with a 225 thruster max. Thus, when targeting specific energy systems, power or capacity, it is important that the load be individualized. Also, we will tend to fall into the exact same work to rest ratios and time periods for different training goals. For example, we’ll always do either full recovery for alactic power and we’ll do 60 sec breaks for alactic capacity. Or we’ll always do 15-20 seconds on 40-45 seconds off for lactic capacity. Vary the work to rest ratios and times through your training blocks and even within your training sessions. For example, we could work a combination of lactic power and capacity by doing something like this:

Sets 1-3: 20 seconds on, 40 seconds off

Sets 4-6: 20 seconds on, 50 seconds off

Sets 7-9: 20 seconds on, 60 seconds off

This would allow for a little more recovery as energy stores are progressively depleted and thus a little higher output. Or it could be reversed to create a greater stress on the energy stores and therefore stress lactic capacity more. Finally, remember that ATP stores and glycogen are depleted within the working muscle group. If two movements with the same working muscle groups are trained together, the total energy depletion will be greater than movements with opposing muscle groups. For example, if GHDs are paired with a kettlebell swing, the energy stores of the posterior chain are not going to be as recovered as if the GHD was paired with a standing dumbbell press. The goal should determine the paring.

I hope this article brought some insight into the nuances of programming for a multi capacity sport like CrossFit. If you have any questions, please let me know below. Remember, don’t just test your fitness, build your fitness.

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