Energy Systems

-In the world of training, there are numerous forms of conditioning that can benefit performance. In order to get the most of out training one must know which conditioning method is most appropriate, in order to achieve their training goals. When training you can target one of three energy systems: the phosphagen system, anaerobic glycolytic system, or oxidative (aerobic) system. I use the term “target” loosley, this is because we use all three energy systems all day, no matter if we are training or not. All three systems play into each other, but focusing on one system specifically will primarily improve the performance of that system.

-After reading this blog, you decide to get up and sprint as fast as you can for 40 meters. How did you come up with enough energy for that activity? You just utilized the ability of phosphagen system. This system is a fast acting system and it does not require oxygen to generate energy for work, so it falls under the anaerobic training umbrella. Any activity performed for 1 to 10 seconds relies on the immediate functioning capability of the phosphagen system. The direct breakdown of adenosine triphosphate (ATP) and utilization of creatine phosphate (CP) are the primary suppliers of energy. The supply of ATP at any given time is enough to sustain activity for a few seconds. Introducing CP allows the replenishment of ATP to match energy demands without the need for oxygen. This is important because the utilization of oxygen for energy production takes a relatively long time. The cost of rapid ATP production to match high energy demands is substantial, and can only be maintained for a few seconds.  Without the phosphagen system, we would be unable to perform explosive movements such as: short sprints, weight lifting, swinging a bat, and throwing a ball.

-After your 40 yd dash, you decide you want to run 400 meters as fast as possible. It is a little more difficult, the ability to maintain absolute maximal velocities starts to decrease, and when you stop you are probably winded. The world record for the 400m is 43 seconds, but for most of us, we can accomplish that task in about 60 seconds or longer. Either way, oxygen intake still hasn't caught up to meet energy demands of the run, so you are still performing under the anaerobic umbrella. However, the ATP used during the first few seconds has been “used up” (at least what our body allows us to use), so how do you continue to run without collapsing after 10 seconds? Well, you can thank the anaerobic glycolysis system for your continued running capability. Fast (anaerobic) glycolysis breaks down carbohydrates without oxygen to produce ATP. The rate at which this occurs is not as fast as the phosphagen system, but the amount of energy produced is much higher. This system takes over after about 10 seconds of work, and will continue until ~ 90 second mark, depending on intensity. Pyruvate is a product of glycolysis, and if training intensity is high enough, it will be converted to lactate as another mechanism to help replenish ATP faster. Carbohydrates, CP, and lactate are the primary sources of fuel for the anaerobic glycolysis system. Training this system requires repeated bouts of high intensity work such as: repeated moderate distance runs, a gymnastic routine,  a shift on the ice for a hockey game, or a 100 m swim.

-Now that you have sprinted 40m , ran 400m, you are feeling extra ambitious. So, you decide why not run a mile (1600m). The training intensity has decreased, and you are sustaining work for a extended period of time. Oxygen has time to be delivered to working muscle, and is in sufficient quantities to aide in the production of ATP. Slow (aerobic) glycolysis is the breakdown of carbohydrates into pyruvate, the difference between fast glycolysis and slow glycolysis is training intensity. If intensity is low enough the pyruvate is shuttled to the mitochondria of the cell, and uses oxygen to resynthesise ATP. The process takes longer, but can be maintained for a much longer duration. The yield of ATP synthesised is much greater, and more efficient, but as mentioned previously it is a slower process that requires several more reactions to occur. Carbohydrates, and fats are the primary source of energy in this energy system. Training this system requires longer durations (90 seconds and beyond) of a  steady work rate such as long distance running, swimming, or biking.

-This is a general overview of the primary energy systems utilized throughout the day and in training. Each is required by the other to function appropriately. There is much more that comes with the description of these systems, and there are many variables that must be accounted for when targeting a system to improve its capabilities. The adaptations that happen as a result of targeting each system is specific to what you target. A marathon runner will not have the same training regimen as a baseball player. The primary energy system used for each athlete is different and the required adaptations to perform at their sport is different. Moving forward, the next few blog posts will dive deeper into each energy system. I will pick the brain of a few strength professionals, and break down some current research into the hows and whys of training each system to help you make more informed decisions when choosing how to train for your goal.

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