These little blog inputs that I have been seriously neglecting as of late I’ve noticed typically get one of two reviews: 1) It was great, but very condensed or 2) it was a mishmash of personal experience forcefully blended with enough technical jargon to make even a well-spoken British man nervous. So, I’ve decided to take a slightly different tack and instead focus on something that, not only everyone can understand, but also identify-with as well as putting things in terms that reduce the glazing sensation only brought about by that first ingredient of boredom- confusion.
On to business.Recently, I was confronted by an article in Runner’s World Magazine where a coach was telling a client to estimate her anaerobic threshold (AT) by running what basically amounted to a 5k and averaging her heart rate (HR) for the final 10mins of the run. I sat back, pondered for a second, and began a hateful letter to the editor of Runner’s World about why they would allow something so blatantly false to appear between the bindings of one of the most widely accepted periodicals in endurance sport. From a metabolic standpoint, that advice could be likened to a nutritionist informing runners that the best way to dietetically prepare for their “A” priority race is to shotgun a gallon of whole milk 15mins prior to the start. However, in my opinion, the above strategy recommended by Runner’s World would in some cases be much more severe because this was their basis for determining season-long training zones.
So, let me explain why this method for finding AT is so limiting. First of all, anaerobic threshold is the point at which your muscles are forced to begin expediently producing energy in light of a continually diminishing supply of oxygen. Here’s something you may not have known. You’ve probably heard for quite sometime that oxygen is critical to exercise, but to truly understand why, think of an engine in a car. The engine consumes fuel and as a result, energy is produced. But, the byproduct of this catalyzation is heat and lots of it, which if left unchecked will slowly erode at the engine’s performance over a given period of time if not stop it altogether. To counteract this problem, you have a radiator circulating water around the engine to absorb the byproduct heat and keep the engine running at its maximal efficiency. This is the EXACT job duty of oxygen. When you produce energy aerobically (with oxygen), your muscles begin a massive cascade of cellular events which eventually terminates in the production of energy (in the form of adenosine tri-phosphate [ATP]). However, there are some byproducts that form along the way which will decrease the efficiency of the muscles if, just like the car engine’s heat, they are left unchecked. This byproduct in the “aerobic form” is very similar to the byproduct in the anaerobic form, which you have probably seen represented as a “H+” in numerous references without even knowing it. Think of the term “pH”. pH is a measure of acidity. The higher the acid content (H+), the higher the acidity. The lower the (H+) content, the lower the acidity. Remember this in just a second… Now, on to the point. Acid, as you know is corrosive, it interferes with the biochemical processes that produce energy in muscles, and causes the pain that you feel during hard efforts. What you may not know is that when you exercise aerobically, you are STILL producing small amounts of acid even though you are exercising below your AT. The acid is a different form, yes, than the acid you produce while exercising above your AT, but the effects are STILL the same. Think of it like this. If you own a factory producing golfballs and Tiger Woods calls up and wants 30 million of them by the end of the week, your factory had better begin working at maximal capacity to fill the order with time to spare. So to maximize productivity you as the owner had better create an excellent environment in which your employees can work if you expect a higher-than normal level of production. The same situation exists in the muscles (and more specifically in the mitochondria, which serves as the vessel for the extent of this process). When exercise intensities increase, you require more energy from your muscles than you naturally would at rest. Therefore, the working conditions inside the muscle had better be optimal or their overall productivity will be compromised if not halted altogether. Because the environment is becoming increasingly acidic with time, all those little biochemical reactions critical to aerobic ATP production start becoming unhappy. Just like the workers inside your golfball factory, if the temperature starts to rise to the point it becomes uncomfortable, you had better find some ventilation- and quick. You’ve got a HUGE order to fill.
Luckily, we have a very effective helper that takes care of this issue of acidic buildup before conditions inside the muscle become intolerable. Oxygen. Oxygen, as you may not know, is incredibly good at neutralizing this situation and restoring optimal working conditions inside your muscles. Here’s why. Oxygen is one of the most incredibly negative elements on the periodic table carrying a -2 charge around with it wherever it goes. Basically, it’s looking for 2 buddies to help bear the load of the negative burden. Interestingly enough, H+, the bad guy in this situation whose population is out of control, carries a +1 charge. Now, if you kind of get where I’m headed and you carry a basic understanding of arithmetic, you’ll have noticed that oxygen is capable of picking up 2 of these H+’s thus decreasing their population, reducing the acidity inside the muscle, and making all of your workers happy by improving working conditions.
For those of you that paid attention in class back in the 6th grade, can you tell me the common name for this molecule? I’ll give a hint. The chemist’s name for it is “di-hydrogen monoxide”. Still no? How about this- Water. That’s it, basic H20. That’s oxygen’s sole responsibility – finding a suitable alternative for the increase in acid content within the muscle. Remember capillaries, red blood cells, haemoglobin, myoglobin, iron…. Yeah, all of it exists for this ONE simple purpose- to transport oxygen from the atmosphere to the muscles where it’s circulated just like the coolant in a car’s radiator to remove the byproduct of aerobic respiration.
It’s really quite extraordinary if you sit and think about exactly WHY you need oxygen. Most people, when they attempt to answer this question, trip all over themselves trying to find a suitable explanation when all they do is leave themselves, and their audience, with more questions. But the answer is simple. Oxygen isn’t fuel, and it can’t be “burned” for energy like most people think. If that were the case, there would be zero need for carbohydrates or fat. It’s sole purpose, it’s only function is to keep the delicate system of aerobic respiration in balance and running efficiently by clearing the byproduct of ATP production.
To sum up everything above, the speed of aerobic respiration is governed by the presence of oxygen, which has MAJOR implications for endurance athletes. Basically, aerobic respiration can only run as fast as the supply of oxygen is plentiful. At this point, if the demand for energy increases when the capacity of aerobic respiration is maxed out, then the body is forced to recruit anaerobic respiration to help with the energy demand. At this point, you become anaerobic, and start generating massive amounts of lactic acid. Because there is little oxygen to stem the acidic onslaught at hand, your body relies on other defensive mechanisms that I shall clarify in act II of this saga. The point is this- if you simply had more oxygen available at the point you begin needing the help of anaerobic respiration, you could have put off the onset of lactic acid buildup thus increasing your aerobic efficiency and overall aerobic power.
So, to complete this circle- Remember my anger of Runner’s World editor X who approved the so-called “anaerobic threshold” test where you run as fast as you can and then average the last 10mins of your HR? Well, here’s the problem with that. You will NEVER perceive the point at which you go anaerobic. It’s a biochemical switch that cannot be “felt”. It can only be registered by equipment sensitive enough to detect the onset of lactic acid – the tell-tale sign that you’re anaerobic. When you exercise with an increasing intensity, the only sign that we have for perceived exertion is our respiratory rate, which really serves as the “top end” of our athletic abilities. As your intensity increases, so does your respiratory rate, but very rarely is there ever a marked increase in respiratory rate when you hit and surpass your AT. Your breathing only becomes labored quite near your VO2max. Using this value as the basis for your anaerobic threshold, as Runner’s World might lead you to believe, would mean that nearly all of your sub-lactate efforts would STILL be in excess of your AT. Why is this is a huge problem? If you never exercise below your AT, where oxygen is still heavily relied-upon to keep everything running aerobically, your body never has any justification to increase your oxygen-consuming abilities. Have you ever gone to a gym and seen the typical gallon jug-carrying, cut-off camo shorts-wearing, wanna-be body builder? Their upper bodies are massive. Their lower bodies- Non-existent. Why? Well the answer is simple. Doing “bicep curls for the girls” has little effect on building their quads. Being that training upper body muscle groups occupies the lion’s share of their attention, their lower bodies simply waste away into oblivion. The same is true on a biochemical level. If you exercise at high intensities- intensities well above your AT, your body has little justification to increase any of its oxygen consuming abilities, and thus, your aerobic potential becomes analogous to a body-builder’s “chicken-leg syndrome”.
So, by employing the all-to-common AT elucidation formulas that you may have read about in your favorite workout magazine (and I’m not just picking on Runner’s World here), you’ve just dealt yourself a crushing aerobic setback. The point is this, if you don’t want to use more appropriate, more precise methods of determining AT through VO2/metabolic testing, then please make sure that when you participate in a field test, you take about 75% of whatever your “final-10min HR” turns out to be (and even this applies to only a small percentage of athletes). By doing so, you guarantee that any workout designed with aerobic adaptation in mind turns out to be precisely that, and not just another exercise in anaerobic futility.