Respiration, Glycogen, and any time anyone ever says “Anaerobic Threshold”

Having taken a couple of advanced microbiology classes in an ill-fated attempt to get into veterinary school, I sometimes have a skeptical attitude towards trainers and their understanding of biology. So, for a brief moment, I will put on my science professor hat and I will step us through some of this jargon.

Firstly, we have to understand why we breathe. Oddly enough, this is never explained by any training material but it has an important relationship to exercise. Oxygen, as we all know, is needed to us to live. Few people can pinpoint exactly why that is. In order to understand that, we have to get microscopic. In order to for cells to do their jobs, they need to go through a process called cellular respiration. In this process (you might have some nightmares about terms like the “Krebs Cycle”) cells generate a substance called adenosine tri phosphate or simply ATP. ATP is what gives the cells the ability to do their respective jobs. The waste product produced by respiration (more properly, the electron transport chain) is an electron in the form of a carbon atom which is removed from the cell via oxygen. Now your brain is firing away connecting the dots of knowledge that you already had – you breath out carbon dioxide.

You might think – “Well that is all well and good, but what if I hold my breath?” Which is an excellent question because you can stay conscious holding your breath even after your body is starting to be deprived of Oxygen. Of course, the body has another way of producing energy. Fermentation, broadly, does the same thing except it produces lactate as a waste product which is removed from cells using completely different system.

Aerobic processes produce far more ATP than fermentation. However, it is not perfect. Some cells do not have mitochondria and therefore will never participate in aerobic respiration. The production of ATP through the electron transport chain, while efficient, isn’t exactly like a factory where it can simply work faster. If the body exceeds the ATP needs of aerobic respiration or if the body rapidly requires the use of more ATP, then fermentation is the only option the body has.

Now for the “anaerobic threshold” which is on everyone’s’ tongue. Put simply, untrained athletes require much more ATP than a trained athlete does, as a result, for the same amount of work (say, running a 5K in 30 minutes) an untrained athlete’s body will resort to using fermentation for making energy for the same amount of work. The resulting soreness in the untrained athlete is the buildup of lactic acid.

Keep in mind that I drastically simplified this process so it can fit into a blog length post. I use the word “fermentation” instead of “anaerobic” because technically anaerobic means not in the presence of oxygen. Although it is splitting hairs, fermentation and ATP production using oxygen happens at the same time in the cell. Therefore oxygen is present and is not technically anaerobic. Fermentation is the chemical process used to produce acid from sugar whether oxygen is present or not.


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