Physiology 101

Energy systems

Muscle contraction is fueled by breaking down adenosine tri-phosphate (ATP) into adenosine di-phosphate (ADP) and phosphate (P), which produces energy. This ATP then needs to be reformed, and that requires energy .

There are 3 different energy systems that are used to build ATP:

1. The oxidative, or aerobic energy system. This system is primarily used for efforts lasting more than 2 minutes and requires oxygen, which is used for mitochondrial respiration. The main fuels for this system are fats and carbohydrates. For a workout lasting more than 2-3 hours, proteins are also used as fuel.

2. The anaerobic glycolytic, or anaerobic lactic energy system. This is the system primarily used for efforts lasting between 20 seconds and 2 minutes, which makes it particularly important for roller derby, as jams usually last 2 minutes or less. The main fuel for this system is glycogen (the polymer of glucose), which is stored in muscles, the liver, and red blood cells. Glycogen is broken down into pyruvate, releasing energy used to build ATP. In the presence of enough oxygen, the pyruvate is oxidized as part of the aerobic system. In low oxygen conditions, however, the pyruvate is converted to lactic acid, a process which releases hydrogen ions, the culprit for the burning sensation in your legs during an intense jam.

3. The phosphagenic, or anaerobic alactic system. This system is very short in duration: 3 to 30 seconds max, depending on training level and individual differences. In addition to being anaerobic (not needing oxygen), this system is “alactic”, meaning it does not produce lactic acid. Rather than use carbs, fats, or proteins to power the re-synthesis of ATP, this system breaks down creatine-phosphate (CP), another energy-rich molecule. This process happens very quickly, releasing a high amount of energy all at once, but does not last long, as the amount of CP available in muscles is small. CP is synthesized in the muscle, but this process requires ATP and takes time. As a result, this energy system is very short-term and requires a lot of rest. A great example of this system is powerlifting, where lifters perform one lift and then rest for a while before their next attempt.


System interactions

This is not all black and white, where one system is being used exclusively while the others rest. Rather, the three energy systems are always interacting to replenish the stores of ATP. Some of these interactions are particularly important for roller derby:

1. Where the effort produced during jams relies heavily on the anaerobic glycolytic energy system, the ability to recover during jams comes from the efficiency of the oxidative system. An athlete with a well-trained oxidative system will be able to consume more oxygen over a shorter period of time. This allows the athlete to use the relatively infinite resources of the oxidative system to help replenish the more finite components of the phosphagenic and lactic systems to produce more ATP. In plain English, better endurance (oxidative system) leads to better recovery between jams and less fatigue toward the end of a game.

2. The pyruvate produced during glycolysis also helps convert some of the lactic acid back into glucose, which can then be used again for glycolysis. One enzyme that facilitates the rebuilding of glucose is oxaloacetate, which is actually marketed as an anti-aging supplement. Without going too much into the science of it (LINK TO, oxaloacetate plays a big role in the Cori cycle and helps turn lactic acid back into glucose, which can then be used as energy again. I personally use Bulletproof UpgradedTM Aging Formula capsules (LINK TO,which I open and drop about 100-200mg of it in my pre-game drink (1 or 2 capsules). I also take it sometimes before early morning practices on the ice, because not only does it help with lactic acid build-up, but with brain fog, as well.

3. Some studies have shown that CP can be used for ATP production in efforts longer than the 30-second “barrier” of the phosphagenic system. While this system is usually seen as the very short-term system for powerliftering or sprinting, CP can actually be used beyond the traditional limits of the anaerobic alactic system. In fact, when our muscles get tired and the CP reserve is depleted, we will start recruiting larger and deeper muscles, which still have intact CP reserves. A good example of this is a jammer who is exhausted toward the end of a jam, but somehow manages to find the power to do one last juke to get out of the pack and get the points before calling the jam off. In this situation, the jammer likely tapped into the CP reserves from larger and deeper muscles. This is where skating technique is critical, so that you know how to use deeper hip and abdominal muscles when skating, instead of relying primarily on your quads and glutes. In terms of nutrition, it is essential to make sure that your CP stores are high before games (important to watch for vegetarians and vegans particularly). Training the phosphagenic system is important, or you will not be able to dig deep and make that hit or that juke that can make the difference at the end of a game.

So all of this is great, but what does it mean in terms of training?

If you follow a periodized yearly training program – which you should – then you will have different successive phases focusing on each of these systems. In the same way we want to build a house with hypertrophy as the foundation, strength as the main floor, power as the second floor and speed as the roof (see last week’s article – LINK), we also want to build a house when it comes to energy systems. The foundation will be made of aerobic training, to develop the oxidative system. Then the main floor focuses on optimizing the anaerobic glycolytic system, which involves a lot of interval training around lactate threshold (LT). Then the second floor is the phosphagenic system, which is where this house and the other house we’re building at the same time (LINK) become very close to each other. Then the two houses actually have a common roof: speed. So when you say that you want to be faster, essentially, you want to build two houses in parallel, slowly and carefully. And only once you have two strong houses can you build the roof of speed. Hopefully, this makes it clear that you can’t become fast without putting in the required time and effort in each phase first. If you were to install a roof on a flimsy house, there’s a good chance that everything will collapse: you will get injured or simply train inefficiently.

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