The Biochemistry of Alactic + Aerobic Training - All About ATP
[This is part 2 of many about the details of Alactic + Aerobic training and why you should be doing it.]
Earlier, I discussed the practicality of what we do with A+A training. I want to dig in a little to the biochemistry of our metabolism and see if I can deduce any first-principles that show why we should be doing A+A training. Though, keep in mind that while I love first-principles and theory, the real power of A+A training is in the evidence that it actually works!
Today, I start with "All about ATP."
ATP - adenosine triphospahate (big word!) is the molecular battery of life. If you need energy for anything - macroscopic muscular activity, or microscopic ion pumping - you're using ATP. Note the three P's at the end of the molecule: those are the three phosphate groups (hence, triphosphate)! Chemically, removing the last phosphate from that change releases a lot of energy - it's that energy that gets used to run life.
Tangent: I find this truly amazing. I come from a chemistry and physics background. All of chemistry and physics is just "accounting for energy." We move energy around and watch what happens. Hit a ball with a bat - add energy to the ball - the ball goes flying. I spent half of my graduate school career computing potential energy surfaces and the other half doing quantum dynamics on those energy surfaces. All of that is fancy talk for "accounting for energy." "Energy" is such a fundamental concept that it almost becomes invisible. Sure, I can compute the dynamics of molecules in 3 dimensions (fancy talk for how molecules move) and how application of energy changes their motions to the smallest degree - it's all just physics! But at some point that physics turns into biology - life! How does that happen? Removing that phosphate in the presence of water releases about 30 kJ/mol of energy. But how does that release of energy turn into a person who's reading this saying, "Mike, you're crazy!" It still doesn't make sense to me that it works, but let's just believe it (we are alive, after all, so it does work) - ATP is the fundamental unit of energy in the body. For everything!
Back to the show: Every cell in your body has a small amount of ATP nearby. As you do things (live) you deplete the ATP and need some way to create new ATP. If you deplete ATP faster than you make it, that's when you feel fatigue. There are a bunch of feedback loops that make it impossible to run out of ATP - that's when you die.
Okay, so there's this chemical reaction that happens: [ATP + Water -> ADP (adenosine diphospate) + P + acid + heat + energy (that 30 kJ/mol from above)]. A few things - a byproduct of creating energy is acid A build-up of acid is what causes cellular acidosis and can cause fatigue by slowing down that ATP reaction. It is believed that chronic acidosis can cause lots of health problems. So that probably means that having a low demand for energy is a good thing as you won't make too much acid and you'll be able to clear the acid faster than you're making it.
So if we're burning up ATP to live, how do we make that ATP. Well, we can just put the ADP and P back together. And since chemistry is reversible, we need to put some energy into the system to make it happen. ADP + P + energy -> ATP. We get that energy from the food we eat. And that's not a simple process!
We have three ways to create ATP
1 - Steal a phosphate from creatine phosphate that might be lying around nearby - often called the phosphagen system
2 - Burn some sugar in a fairly complicated reaction - often called glycolysis
3 - Burn some fat (and sugar) in a much more complicated reaction - often called mitochondrial respiration
The first two are often classified as "anaerobic" as they don't need oxygen, and the last one is the "aerobic" pathway that everyone like to talk about.
I'll dig into these in the next few posts. If you've been following along #1 is the "alactic" pathway, #2 is the "glycolytic" or "lactic", and #3 is the "aerobic". For A+A we want to use Alactic and Aerobic and not glycolytic. You'll see why...