How our body caters to various energy demands
The 3 systems that each play their respective role
Before we build a training plan, it is important to consider the different demands that each sport requires. This article aims to discuss how our body uses 3 different systems to account for the various energy demands we ask of it. There are more demands to consider, but understanding energy systems provides a great foundation. For the sake of clarity and intuition, I will use running as the example to explain how these systems interchange, covering the various demands of sprinting, mid-distance running, and long-distance running. We find a lot of similarities in the muscles that are being worked between sprinting and jogging. However, the preparation for those muscles require a completely different strategy. This is why you would never see a marathon runner focused on how fast he can sprint or a 100-meter sprinter focused on his mile time. One of the biggest reasons why is because our body has 3 different energy systems that each play their respective role to a specific demand. I’m going to refer to them as explosive, intermediate, and aerobic. For those who are curious about their scientific names, I will list them at the bottom of the article.
Recruited during maximum output
Primary system during: Sprinting, jumping, throwing, kicking, hitting, heavy/power lifting, etc.
Duration: 0-6 seconds
Work-to-rest ratio: 1:12+
(This means if you sprint for 5 seconds, it’ll take 60 seconds to fully recover)
This system gets recruited when we want to sprint as fast as possible, jump as high as possible, throw as hard as possible, swing as hard as possible, lift as heavy or as fast as possible, so on and so forth. The point being, our explosive system gets recruited when we our asking our body to do something at its maximum velocity. This explosive energy only lasts for 0-6 seconds, explaining why we can’t maintain an all-out effort for very long. This system takes at least 12 times as long to recover as the time that it put in; meaning if an all-out effort of 5 seconds is performed, then a minimum of one minute is needed for full recovery of that system. A trained individual could recover in one minute, but an untrained individual could take almost up to two minutes. The recovery of this system is logistic by nature, meaning the recovery rate starts out fast, but slows dramatically. We can recover almost 70% of its capacity during the first half of our recovery time, but it takes an equal amount of time to recover the last 30%. In sports where bouts of effort last less than 6 seconds, think football, baseball, diving, jumping, throwing, etc., the explosive energy system should have most or all of the attention depending on the sport.
Recruited during a sub-maximum effort lasting less than 2 minutes
Primary system during: Skiing, soccer, basketball, lacrosse, mid-distance sprints, etc.
Duration: 10 seconds – 2 minutes
Work-to-rest ratio: 1:3 – 1:5
The intermediate system is a primary driver in sports that require bouts lasting longer than 10 seconds, but shorter than 2 minutes. Some examples that are heavier influenced by this system include downhill skiing, soccer, lacrosse, basketball and mid-distance sprints, whether that’s swimming, track, cycling, skating, etc. This system lasts anywhere from 10 seconds- 2 minutes, largely dependent on intensity and fitness level. If we took off at 90% of our maximum effort, we would begin to tire sooner than if we were at 60% of our maximum effort, both intensities still demanding effort from the intermediate system. It’s work-to-rest ratio is 1:3-1:5, meaning if we are working for 1 minute, then it would take a minimum of 3 minutes to fully recover that system.
Recruited for an extended effort beyond 2 minutes
Primary system during: Long distance efforts (Running, swimming, biking, rowing, etc.)
Important consideration during: Soccer, rugby, basketball, water polo, etc.
Duration: Infinite as long as the body is taking and transporting oxygen
Work-to-rest ratio: 1:1 – 1:3
The aerobic system has a clear distinction from the other two in that it requires oxygen to function. Its performance is directly influenced by the body’s ability to transport that oxygen throughout the body and is the only system at play when we are purely focused on distance. Its duration is infinite as long as the body is still inhaling and transporting oxygen. However, the sheer act of inhaling and transporting oxygen is much more complicated than just breathing. Our hydration, nutrition, altitude, and training level are just a few of the factors that affect our ability to do so. This means that for an endurance athlete, it doesn’t make much sense to focus on how high we can jump or how fast we can sprint, but rather to spend that time increasing our oxygen transport efficiency.
How does understanding these 3 energy systems help us?
If we want to train a specific system, we must know when we are no longer working in it and also how much recovery is needed to remain working in that system. When we push past 6 seconds at maximum effort or when we don’t allow for that system to recover fully, our body simply transitions into the next energy system. If we ran all out for 1-2 minutes, we could expect a drop in speed between 4-8 seconds, more dramatic in an untrained individual, and another drop in speed somewhere between 30 seconds-2 minutes. Following that last drop in speed, the system that would be taking over would be the aerobic system, carrying us as far as we continue. What we are feeling during those dips in speed is our body transitioning energy systems. The first transition from explosive to intermediate is typically very noticeable, while the transition from intermediate to aerobic is more gradual. The other example of this concept is shown if we run a series of 10 second sprints, only resting for 1 minute between each. What we would eventually notice is that each subsequent rep becomes slower than the last. This is a clear indication that we are transitioning into another system.
Why can’t we maximize our sprint and distance efficiency at the same time?
We lack the ability to max out each respective energy system at once, and we also lack the ability to create new muscle fibers. To learn more about muscle fibers, read the article “Muscle fibers: how to prepare for speed, endurance, and strength.” Every second we spend working one energy system and muscle fiber type, we are either neglecting or degrading another. If we spent one month focusing on running a 10k, we’d find that we no longer can sprint as fast we used to. In contrary, if we spent that same month focusing on maximizing how fast we can run 50 meters, we would lose a lot of aerobic capacity, affecting our ability to run long distances. This is especially important because we often times don’t think of how a 2-mile run or lifting heavy weights could affect us negatively. Most people measure the effectiveness of their training by how hard they were able to push themselves, after learning how our energy systems work, this couldn’t be further from the truth. The effectiveness of our training should be directly measured by the specificity of it. How hard we went or how exhausted we feel after a workout tells us very little about how effective we are. We certainly want to maintain progression, but we want to be sure we are progressing in the right direction.
What does all of this mean when applying it to our lives?
First, we have to answer some questions.
What sports/activities do I engage in?
What are the durations of work and rest?
A good example for this question is football in which an average play lasts 3-5 seconds (work) and the average time between plays is 30 seconds (rest).
Do I engage in multiple sports/activities in the same season?
How do I balance my training to meet all the demands?
Are the demands similar or antagonistic (work against each other)?
Once these questions have been answered, then it becomes much easier to develop an optimum training strategy. In a lot of sports such as soccer, the training becomes much more complex because you have antagonistic demands. This requires a tedious training strategy that balances attention between the explosive demands of sprinting, kicking, jumping, and throwing, while also giving time to building both an intermediate sprint capacity (holding a 60-90% sprint), as well as an aerobic capacity (maintaining energy through an entire game). This is seen in other sports such as basketball, lacrosse, tennis, rugby, etc.
In summary, we have 3 different energy systems that each play their respective role in catering to the demands we ask of our body. These systems are all intertwined and limited based on both our genetics and training. If we train for aerobic capacity (distance), we will be negatively affecting our explosive and intermediate capacity and vice versa. This is due to the correlation between our muscles and energy systems. Read “Muscle Fibers: How to prepare for strength, endurance, and power” to learn the role that muscle fibers play in this equation. Each energy system has specific work-to-rest ratios and they are as follows:
Explosive system- 1:12+ (If we work for 5 seconds, it would take at least 60 seconds to fully recover)
Scientific names (Phosphagen, Creatine Phosphate, Phosphocreatine, or Alactic)
Intermediate System- 1:3 - 1:5
Scientific names (Anaerobic Glycolysis, Lactic Acid System, Anaerobic Lactic)
Aerobic System- 1:1 - 1:3
Scientific names (Aerobic Glycolysis, Oxidative)
For sports that are purely explosive and don’t require repetitive bouts such as throwing or jumping in track & field, training any system other than our explosive one is going to hinder progression. On the contrary, for sports that are purely aerobic such as distance running, swimming, or cross-country skiing, training any other system then aerobic will hinder progression. Keep in mind that aerobic training doesn’t purely have to be long distance. We can still aerobically train by doing high intensity intervals with short recovery periods. The main thing to consider are the demands of our sport, if they require more than one demand, and if those demands are antagonistic. If they are antagonistic, then we must spend time training each system separately if we want to maximize each.
Nicholas S. Beauchamp, April 2020
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