Your Training and Energy Systems

By Chris Daly 

Knowing why we feel the way we do during a training session can be attributed to many different variables. Today I’m going to touch on one of them: your body’s various energy systems. Understanding when and how they are used can increase the effectiveness of your training.

First, we need to understand how our bodies utilize fuel sources and how those different fuel sources create energy. When we consume food with carbohydrates, those carbohydrates are immediately broken down and converted into useful energy. After this energy has been used up, our body will begin to break down glucose from our muscles and liver, known as glycogen. After glycogen depletion, the body starts breaking down fat stores in fatty tissues. Diet plays a major role in energy production (imagine that)!

Now that you have a general understanding of how food affects energy production, let’s talk about the 3 main energy systems our bodies utilize. First off is the ATP-CP (Adenosine triphosphate – PhosphoCreatine) system. Think of this as the system that we use for anything up to 20 seconds in duration. This period is also known as alactic, or before the production of lactate. As such, the first 10 seconds of these efforts is often referred to as alactic power. Things that would fall into this type of training would be sprint efforts (think assault bike, sprint running, rowing or attempting 1RM lifts).

This energy system also depends largely on what type of athlete is performing the effort. More powerful athletes produce more force and require longer recovery while newer athletes may not be able to effectively train the ATP-CP system initially. Typically, recovery for this type of training would be 12-15 times longer than the duration of work. If the athlete in question is performing 20 seconds of row sprints at max effort, the rest could be 240 seconds or longer. Total work can vary anywhere from 4 to 6 sets as long as that work is consistent and repeatable. If the athlete proves capable of repeating effort across all sets, more sets and blocks can be added weekly. Training utilizing this energy system takes longer to recover from during the week, but can be beneficial leading up to the CrossFit open or as preparation for other competitions. Some sports and activities also require being able to exert maximal effort and recover repeatedly.

After around 20 seconds of work, your body starts to move into the Glycolytic system, also known as the Anaerobic Lactic system. This system is mainly responsible for activities up to 2 minutes in duration. The presence of Lactate (produced from the breakdown of glycogen) is a key aspect of this energy system. Training in this system would include things which tend to be lower-skill movements and could not be sustained at their pace for longer than 2 minutes. Again, this all depends on the athlete, but these movements would include rowing, burpees, wall balls, etc. Rest periods for this type of training could be equal to the work performed or vary between 3 and 7 times as long as the work interval. Rest required is always dictated by the athlete performing the work and the goals of that training piece. Sets are added as needed as long as the efforts are repeatable. Training in this system builds pacing mechanics while allowing work to be done at a higher level of effort.

The first two systems are considered anaerobic because they happen without the presence of oxygen. The last system is called the aerobic system because it utilizes oxygen in energy production. This encapsulates workouts or training events lasting the longest in duration. Having a good aerobic base also allows us to recover faster during workouts. These training sessions would typically be performed at a sustainable effort and generally include a lower power output. Training this system could include multiple AMRAPs of 10+ minutes, 20-30 minutes of biking, rowing, or running, and could also include some barbell and gymnastics work.

Any effort can become aerobic depending on the ability of the athlete in question. Rest periods could range from as much as needed, to equal to the work interval, to as high as multiple hours (depending on the event). These training sessions could be done in a separate morning session several days a week, as active rest days or after other training (depending on the athlete’s goals). Lastly, a good way to think about training for longer workouts would be taking the time domain of that workout (i.e. 20 minutes) and performing smaller rounds lasting 25 percent of that time. For example, think about performing 4 rounds of 5 minutes of work and pacing those rounds at the desired 20-minute pace.

In summary, even though there is an order in which the energy systems turn on, all three systems are used during any activity. In large part, training intensity determines which systems are being utilized even though, in reality, it is always a combination of the three. Even though the systems work together, order and frequency of training are also important.

Regarding the anaerobic systems, power should be trained first followed by endurance.

Conversely, endurance takes precedence before power in the aerobic system. Quite

simply, getting stronger makes you more powerful. Once you can exert that power

during 20 second sprints, you can then build up your endurance in those sessions.

On the aerobic side, building up your base can lead to being more powerful on those efforts. As you gain the ability to do more work, you can increase the amount of power expressed on that work and thus increase the overall intensity. Total sets, time, and rest can all be manipulated weekly depending on your ability to repeat and sustain effort.

There really is no one way to train; it all depends on the goals of each individual athlete and the activity in question. For general fitness, being able to perform short bursts of max-effort reps, being able to sustain a steady pace and repeat that effort, and being able to recover between efforts are all important. Blending these things into a meaningful program is something we as coaches here at Invictus Boston find especially important!

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