Aerobic exercise, anaerobic exercise, and the relationship between the two.

This is a thing I've been wanting to circle back to for a bit, and I'm putting it in my blog despite the fact that it might be a short post, because I want to include references for future-me.

In general, what I'm trying to express here is the reason that I, personally, need to train cardio. This requires an overview of how aerobic and anaerobic exercise work, as well as a bit of a dive into the biochemistry of energy production.

The tl;dr of how I think about it is that anaerobic muscles create energy debt, while aerobic muscles pay it back. This one-sentence breakdown isn't the full story on the subject - it's not as though all muscles or exercise are completely one or the other. But it is a shorthand of the full version.

(As a note, I definitely can't figure out how superscript works in the new Blogger format, so I'm just going to bold-italicize references unless I decide to go back and fix them in the HTML view thinger.)

One last note before the body of the thing - I am no scientist, so it is likely that I got some parts of this wrong. Please, if you have the expertise to do so, let me know where I'm wrong. I want to gain knowledge, and being told where I'm wrong is a wonderful way to do it.

*****

The traditional wisdom around exercise is that we have two muscle types:

    short-twitch fibers, used anaerobically for quick and hard movements, creating energy by consuming lactic acid which is then processed into sugar by the liver.
    long-twitch fibers, used aerobically for slower movements, using oxygen to produce energy in a more efficient way using mitochondria to process sugar.

Sure, there is also the smooth muscle of the heart and organs, and the mixed types of muscle fibers. But in general, this is the way that things are outlined, and these muscle fiber types are talked about as though they are completely different systems. In reality, these muscle types operate together both in a physical power-generation level, and on a chemical energy-generation level. This is why for someone like me, for whom the limiting factor in running is not the strength of my legs, it is important to do aerobic exercise in order to increase both aerobic and anaerobic muscular capacity over time.

The energy currency of the body is ATP. This is what our organs, muscles, and brains use to do things. We can produce ATP through two ways - using oxygen or not using oxygen. Using oxygen, we net 38 molecules of ATP per glucose molecule. When not using oxygen, we only net 2 molecules of ATP per glucose. However, the latter reaction is 100x faster. (7) Looking at this in the inverse - this means that committing glucose to aerobic energy production will produce about 1/5 of the energy that would be created by that same glucose anaerobically, in a very short time-frame.

The aerobic method of energy production does produce some waste products, but overall it is very efficient and those waste products are removed from the body. The anaerobic method, however, produces lots of lactic acid, which can be disposed of in two ways.

The first, and most commonly-mentioned in textbooks, is that the liver processes lactic acid back into glucose, consuming ATP to do so. From there, the glucose can be used aerobically by the liver and other tissues of the body.

The second method is removal by other skeletal muscle. (1) Primarily-aerobic muscle is more likely to take in lactic acid from the bloodstream (4). From there, lactic acid forms lactate and is eventually oxidized into pyruvate, and can be taken directly into the early stages of the citric acid cycle, which is the aforementioned means of producing 38 ATP from one glucose - still producing most of the ATP that it would have otherwise produced.

This means that not only does one's ability to clear lactic acid improve as one gains more slow-twitch or aerobic musculature (5), that same lactic acid is used by that musculature to produce more energy.

(As an aside - apparently lactic acid is not actually the thing which causes muscles to burn. It's free hydrogen ions, produced as part of anaerobic effort, which get used to combine with lactic acid to form lactate.)

This is why aerobic exercise is important. Because the more aerobic musculature you have, the more energy-per-second you can produce. While anaerobic exercise improves on-demand power production, aerobic exercise is what increases one's ability to both produce power over a longer period of time, and to recover from the debts incurred to yourself by doing anaerobic effort.

(As another side note - your body is always doing anaerobic effort. The smooth muscle of your heart primarily gains energy anaerobically, which means there will always  be at least some small amount of lactic acid being produced. (6))

As an aside - the ability to process lactate is important to mental health too. In the brain, it behaves as a neurotransmitter. When infused into the bloodstream, it causes panic attacks. (8) Given that the blood-brain barrier allows lactate to pass easily (9), it would make sense that muscular capacity to oxidize lactate into pyruvate would be useful for reducing anxiety by reducing lactate build-up.

(Edit: Aww dang, I meant to mention that apparently the body chugs through lactate faster if you are doing some amount of exercise - for rowers, something like 40% speed was best for faster recovery, even better than full rest (3). So, ignoring that I have no idea how this interacts with heat sensitivity, you will recover faster if you walk around or something after you get done doing something super strenuous.)

*****

As a final side-note, doing the research for this post makes me wonder if there is a system in the brain parallel to fast-twitch and slow-twitch muscles. This would be anxiety-driven versus relaxation-driven thought and action.

As someone with ADHD, I often find myself completely unable to motivate myself to do anything without a deadline or some sort of anxiety looming over my head. Given that lactate, glucose, and pyruvate can all cross the blood-brain barrier to some degree, it would make sense that they could influence the type of thinking one does. They are also all able to be consumed as fuel by the brain.

It would make a kind of sense that the brain would get used to using and producing one type of fuel or another. I wonder if this would create metabolic changes in the brain in the same way that working aerobic or anaerobic musculature increases your capacity to do aerobic or anaerobic work.

*****

A BUNCH OF SOURCES:
(yes I realize I'm mixing citation types and no I will not fix it)

(1) Pagliassotti MJ, Donovan CM. Role of cell type in net lactate removal by skeletal muscle. Am J Physiol. 1990 Apr;258(4 Pt 1):E635-42. doi: 10.1152/ajpendo.1990.258.4.E635. PMID: 2110420.
https://pubmed.ncbi.nlm.nih.gov/2110420/ 

(2) Lactic acid recovery profiles following exhaustive arm exercise on a canoeing ergometer S.J. Baker PhD and N. King BSc
https://bjsm.bmj.com/content/bjsports/25/3/165.full.pdf 

(3) Koutedakis, Y, and N C Sharp. “Lactic acid removal and heart rate frequencies during recovery after strenuous rowing exercise.” British journal of sports medicine vol. 19,4 (1985): 199-202. doi:10.1136/bjsm.19.4.199
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478395/ 

(4) Juel, C, and A P Halestrap. “Lactate transport in skeletal muscle - role and regulation of the monocarboxylate transporter.” The Journal of physiology vol. 517 ( Pt 3),Pt 3 (1999): 633-42. doi:10.1111/j.1469-7793.1999.0633s.x
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2269375/ 

(5) MacRae HH, Noakes TD, Dennis SC. Effects of endurance training on lactate removal by oxidation and gluconeogenesis during exercise. Pflugers Arch. 1995 Oct;430(6):964-70. doi: 10.1007/BF01837410. PMID: 8594549.
https://pubmed.ncbi.nlm.nih.gov/8594549/

(6) Barron JT, Parrillo JE. Production of lactic acid and energy metabolism in vascular smooth muscle: effect of dichloroacetate. Am J Physiol. 1995 Feb;268(2 Pt 2):H713-9. doi: 10.1152/ajpheart.1995.268.2.H713. PMID: 7864198.
https://pubmed.ncbi.nlm.nih.gov/7864198/

(7) (stolen reference from Wikipedia) Stojan, George; Christopher-Stine, Lisa (2015-01-01), Hochberg, Marc C.; Silman, Alan J.; Smolen, Josef S.; Weinblatt, Michael E. (eds.), "151 - Metabolic, drug-induced, and other noninflammatory myopathies", Rheumatology (Sixth Edition), Philadelphia: Content Repository Only!, pp. 1255–1263, ISBN 978-0-323-09138-1, retrieved 2020-11-02

(8) Riske, Laurel et al. “Lactate in the brain: an update on its relevance to brain energy, neurons, glia and panic disorder.” Therapeutic advances in psychopharmacology vol. 7,2 (2017): 85-89. doi:10.1177/2045125316675579
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5315230/

(9) Knudsen GM, Paulson OB, Hertz MM. Kinetic analysis of the human blood-brain barrier transport of lactate and its influence by hypercapnia. J Cereb Blood Flow Metab. 1991 Jul;11(4):581-6. doi: 10.1038/jcbfm.1991.107. PMID: 2050746.
https://pubmed.ncbi.nlm.nih.gov/2050746/

Skill Improvement for ADHD Brains with a TL;DR List

 Earlier today, I wrote a comment in response to a post on reddit about how to improve when you have ADHD. As someone who has ADHD and is pretty okay at a number of skills, I thought I would put that comment here too, since that's what a blog is for.

 Enjoy!

*****

I have ADHD-PI, and here is a bunch of actionable advice I've used with myself for improving at skills. Since we all have ADHD here and are likely to type much more than we're willing to read, here's a tl;dr:

TL;DR BULLET POINT LIST

• Cultivate relaxed, sincere interest
• Don't over-read
• Don't over-train
• Don't keep playing when in a bad headspace
• Get exercise

I'm not amazing at the game, but I do have other competitive things I'm good at. Generally I try to cultivate a "relaxed, sincere interest" in things I want to get better at. If I try to force my brain to focus on the game, then I end up beating myself up about not doing things correctly. That teaches my brain that playing the game causes suffering, thus making it harder to focus. If I relax and let my brain think about the things I love about the game, that means my brain is more likely to stay engaged.

Honestly, having too much knowledge about the game that you're not ready to apply can be a hindrance to improvement. If you have too many things you're trying to do, you won't improve at any of them. Maybe try to focus on improving one thing at a time, and try reading about the game less. I've also often found that a lot of what people say online is either not applicable to my play-style, or I'm not ready to hear it yet. If I don't have the skill to pull off something that someone says online, the solution isn't to try harder. The solution is to ignore it until it seems more natural to me. I have often found that advice has made no sense to me, but after playing and improving for a few months, it will suddenly make sense and be the easiest thing in the world to execute.

(As an example - I used to not understand why people loved Ridley's nair so much. I would try to use it, but then it would get stuffed by disjoints. So I stopped trying to use it for a while. Eventually my spacing and match-up understanding improved enough that using nair seemed natural. So I, too, started to love the nair.)

The brain is an associative learning device - that is to say, if you are spending a lot of time playing sub-optimally, the brain will learn to continue playing sub-optimally. If you notice yourself on autopilot, go do something else so your brain doesn't train itself harder to play on autopilot.

Brains require actual physical chemicals in order to improve at skills, and they only produce those chemicals at a certain rate. If you try to improve at a skill when your brain doesn't have any more of the chemicals needed for learning, you won't be able to improve. So don't overdo it, and if you're already tired then don't play very much.

Exercise also improves the rate at which the brain produces these brain chemicals, so doing some sort of exercise can help. Half an hour of cardio per day has been shown to improve the ability of ADHD brains to focus. As well, strength training increases the rate at which the brain produces dopamine, which is one of the brain chemicals needed to learn. Especially if you're starting out, you don't have to do much - just a nice walk is good. 

*****

Again, I hope that y'all had a good time reading this thing. I hope that at the very least the bullet-point list helps some of you.

Have a good day!