Part 1 - Aerobic versus Anaerobic

Introducing this new column on fitness for the fighting arts we take a look at the fundamental concepts of aerobic and anaerobic exercise.

Before you get stuck in to this article please read the disclaimer.

Formulating a definition of aerobic and anaerobic exercise is one of those things that give rise to confusion and, to some extent, argument. What we need as martial artists is a definition that enables us to train more effectively; precise scientific definitions may not be useful or may even be confusing. None the less, any definitions we do apply must have good scientific basis.

Let's start with the bald dictionary definitions of the terms:

  • Aerobic - 1. Depending on free oxygen or air. 2. Of or relating to aerobes.
  • Anaerobic - 1. (Of an organism or process) requiring the absence of or not dependent on the presence of free oxygen or air. 2. Of or relating to anaerobes.

And just to clear up a couple of terms used in the above definitions:

  • Aerobe - An organism that requires free oxygen or air for respiration.
  • Anaerobe - An organism that does not require free oxygen or air for respiration.

So the above definitions tell us that an aerobic process requires the presence of oxygen to take place whereas an anaerobic process does not. Now that's a good start; oxygen usage seems to be the key. However, writers such as Maffetone et al. [1] take the view that we as human beings always require oxygen. It is absurd to suggest that we could take part in any kind of exercise without the presence of oxygen and because of this they suggest that these laboratory definitions of aerobic and anaerobic processes are not useful explanations.

That is not to say that the two definitions are inaccurate. They simply apply to low-level processes such as cellular respiration. Now if you are interested in the finer details of the Anaerobic Phosphagen (ATP-PC) Energy System, Anaerobic Lactate (Glycolytic) Energy System and or the Aerobic Energy System there is a ton of information on the Internet for you to seek out (and very interesting it is too). But for those of us that just want to know how hard and in what way we should be training such information doesn't offer immediate benefits.

Most people are aware that aerobic exercise takes place at lower levels of effort than anaerobic exercise. It is not uncommon to use breathing rate as an indicator; breathing is relatively comfortable during aerobic exercise but anaerobic exercise leads to laboured breathing. That may or may not be correct but it is certainly a very weak definition of the difference between the two processes.

One of the key differentiators identified by Maffetone et al. is that aerobic exercise tends to utilise fat (in the form of fatty acids) to supply energy where as anaerobic exercise uses sugars. This is a well know process cited by other authors:

"Fat is the primary source for fuel at low levels of effort such as a long slow bike ride. As the intensity of effort increases, the body increasingly turns to carbohydrate for fuel, and fat usage diminishes" [2]

And for a more technical explanation see below (for now just accept that ATP is Adenosine Triphosphate, a chemical that is broken down by the body to produce energy):

"Aerobic metabolism, which is oxygen dependent, is the name for several different chemical processes in the cell, and can produce ATP from all three food elements - carbohydrates, fats, and protein. Aerobic metabolism supplies the ATP needed for endurance activities.

Glycolysis, also known as anaerobic metabolism, is limited to the breakdown of carbohydrates (glucose, glycogen). Anaerobic metabolism is limited by the build-up of lactic acid which begins within minutes and degrades athletic performance by impairing muscle cell contraction and producing actual physical discomfort or pain. Anaerobic glycolysis is the source of energy for short bursts of high level activity lasting several minutes at most (sprints)." [3]

Now that's really interesting. If you need or want to loose weight working very hard may actually be the wrong thing to do! That's because at higher levels of exertion you will be burning more carbohydrates and fewer fats.

This business of burning fats versus carbohydrates and the associated levels of exertion have another well known effect. The burning of carbohydrate produces a by-product called lactate. As the levels of lactate build up in the blood stream muscular fatigue results. I think we are all familiar with that hot burning sensation in the muscles as we try to pump out that last press-up. So this becomes another key differentiator between aerobic and anaerobic exercise:

"The level of exertion at which the body shifts from aerobic (light breathing) to anaerobic (laboured breathing) is marked by such rapid lactate production that the body can't keep up with its removal, and lactate begins to accumulate in the blood interfering with energy production and muscular contractions thus causing fatigue." [4]

So let's put everything we know so far together and come up with some working differentiation between aerobic and anaerobic exercise:

  • At a low level aerobic processes require the presence of oxygen whereas anaerobic ones don't.
  • Aerobic exercise takes place at a lower level of exertion than anaerobic exercise.
  • Breathing remains relatively comfortable during aerobic exercise but becomes laboured during anaerobic exercise.
  • Fats (as well as carbohydrates and even protein) can be burned as fuel during aerobic exercise but during anaerobic exercise the fuel is carbohydrate.
  • Burning carbohydrate as fuel such as during anaerobic exercise results in the build up of lactate in the blood which leads to fatigue.

Now this is where our first big problem presents itself. Do you honestly think you can identify with certainty that at any given time you are exercising aerobically or anaerobically? You can say "I'm breathing a bit harder now" or "My legs are beginning to ache" but those are quite subjective responses to physical exertion. What is required is an objective measure of the level of effort you are putting in.

The next problem is identifying whether you need to be exercising aerobically or anaerobically or a combination of the two. If you require a combination of the two in what proportion should they be combined and how should you structure your workout schedule?

These two problems will be addressed in subsequent articles in the Fighting Fit column.

As I stated previously there is a raft of information on the Internet on this subject but here are a few links:

References

[1] 'The High Performance Heart', Dr. Philip Maffetone et. al. , p.17.

[2] 'The Triathlete's Training Bible', Joe Friel, p.39.

[3] 'Cycling Performance Tips, Exercise Physiology, Energy Production in the Cell', http://www.cptips.com/bscphys.htm

[4] 'The Triathlete's Training Bible', Joe Friel, p.38.

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