Disclaimer: This post discusses some topics on muscle, energy, and oxygen science. As you may quickly note, I'm not a scientist nor a doctor but I do have muscle (a few pounds of it) and consume energy (not just electronic). Some of the information could be a bit off base so you may want to consult a true expert on the topic if you want in-depth information.
In my last Hospital Hill Run Blog Team post, I mentioned how I really enjoyed the book "Smart Exercise: Burning Fat, Getting Fit" by Covert Bailey. If you are curious about how the stresses of working out impacts the body, this is definitely a winner. I will warn you that Covert doesn't hold back. He might not be the most politically correct person in this book. So if you are offending by the use of the phrase "fat people", then you might look somewhere else. I will refrain from the terms though.
One of the things I took away from this book was his discussion of aerobic and anaerobic exercise. We've all heard the terms but what does it really mean. How does it come into play when deciding what kind of workout to do? First off, let's start with some definitions:
Aerobic - With Oxygen
Anaerobic - Without Oxygen
Lesson over. Thank you and goodnight.
Ok, maybe more detail needs to be uncovered.
Simply put, when working out aerobically, your body is moving at a pace in which the cells of your muscle burn fuel that requires oxygen as part of the "combustion". This oxygen used is delivered to the muscles through the blood system. At some point, the harder you workout, the more difficult it is for your blood stream to keep up with the oxygen demand by the muscles; therefore, your body converts to using a different kind of fuel that does not require oxygen. It is at this point in which your body is now working out anaerobically; hence, the definition of "with oxygen" (aerobic) and "without oxygen" (anaerobic).
That is simple way to explain it because we haven't really gotten into the most important part of the conversation: fuel.
Fill'er Up!
I liken your muscle cells to fireplaces. Covert Bailey uses a similar analogy but I take it a little further. In order to provide fire you need energy sources. Generally you start out with kindling (sticks, dry pine needles, newspaper, twine, etc) and then move on to actual logs. In the body, there are two main energy sources as well. Sugar (stored in the form of glycogen) and fat cells. The glycogen is equivalent to kindling as fat cells are to logs.
Kindling burns pretty quickly and doesn't take much at all to start. Logs require a lot more effort to light on their own.
Light'em Up
When your body starts to workout, it needs to decide which fuel source to use, glycogen or fat. Just as when you are building a fire. Unless you are a mad wizard at fire building, you will start with kindling to get things going. Your body does the same thing but uses glycogen. The need to "fan the flames" with kindling is generally not needed because it will take off pretty quickly. Similarly, your body doesn't need oxygen to convert glycogen into energy.
After a period of time, your body will realize that you aren't stopping. It will either continue to use glycogen or start using fat cells for its fuel source. Your body is smart enough to know you have a limited amount of glycogen in the body. If it can use fat, it will. How does it decide when to use fat? It depends on your body's ability to provide oxygen to the muscles! If there isn't enough oxygen, it will continue to stay anaerobic and burn glycogen. If it can't, you will run out of glycogen and your body will force you to slow down or stop. Also known as "bonking".
Long Burn
With your fireplace, you will either need to hunt down more kindling or start using larger logs to keep the fire burning, hot and slow.
Similarly, if your body can use fat due to the available source of oxygen, it will begin using fat cells for energy. If your muscles need more fat, it will request it and fat cells throughout the body will be released for use as fuel. If you were to run out of logs, you could go cut down another tree or, in desperation, take apart a couch to throw in the fire. In other words, there is a near limitless supply of fat on the body, unlike glycogen.
Working in Tandem
So I mentioned that if you run out of glycogen, you "bonk". So why is it possible that marathoners (or half marathoners!!) who run at a pace that burns fat cells also bonk? Well, glycogen is also used in the aerobic/log burning phase as well. Albeit in smaller amounts. It sort of helps kick-off the fat burn when new fat cells arrive in the muscles. It is only used in slight amounts compared to anaerobic exercise, but it is used. So you can still run out of sugary glycogen during aerobic exercise and experience that four letter "b" word.
This is one of the reasons it is imperative that during endurance events like half marathons and up to consider mid-race fueling options. Whether you are looking for that strong kick at the end or just trying to keep moving past mile 10... or 20... or 30, you need to keep fueling yourself some form of sugar for your body to convert into glycogen. Many people do this using gel packets like Gu, Cliff Shots, Hammer, etc.
Be a Fire Building WIZARD!
So I mentioned that unless you a fire building wizard, you need to start with kindling to light your fireplace. The truth is, that's the whole purpose of working out. In endurance events, we are trying to make our muscles more effective and efficient at burning fat. We want to burn fat earlier in our workouts. We are trying to make our blood system more efficient at supplying our muscles with oxygen and fat.
You know the phrase "getting in shape"? I don't consider "in shape" an outward appearance but rather shaping our blood system and muscles to be more effective at burning fat.
I will talk more about this benefit of "getting in shape" when I get into heart rate-based training and also during a topic on interval training. I'm hoping to tie it all together for you at that point!
As for now, thanks for stopping by!
Side note: I do realize my comparison of fire from kindling to anaerobic is kind of loose. Yes, any form of fire needs oxygen but let's just suspend that belief a little bit to make my point.
Feel free to stop by and ask questions in the comments or hop over to Twitter to chat me there! You can find me as @ScottyTris.
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