Since the advent of mainstream ventilatory data collection, VO2max, for some reason, has been the quintessential bit of information that makes an endurance athlete feel complete and whole. Granted, knowing that Lance Armstrong’s VO2max is “84” is both as interesting as it is humbling… that’s quite high, for the record. AND, I will admit that the most successful endurance athletes have historically had higher-than-normal VO2max values. However, just about everyone fails to understand that this metric is but one of many key indicators that consolidate the full spectrum of what most physiologists would consider a well-rounded athlete. They place an infinite respect for VO2max and often toss it around like some sort of endurance-related currency. Asking someone’s VO2max, as is the case with asking someone’s annual salary or what he or she scored on the ACT, is just about as common-place nowadays as it is annoying. However, the fact still remains: VO2max is “the” gold-standard that separates those who “will” and those who “might”… but from a training perspective (and I’ve been waiting a long time to say this), VO2max is 100%, totally, and without equivocation, useless.
Before the systemic deconstruction begins, I will start with an explanation – oh, and btw, I have zero disapproval for anyone who is a self-proclaimed VO2max worshipper. I only ask that you approach my argument with an open mind, and if you do, you might learn something that will totally change your current training paradigm. Afterall, VO2max is quite a simple concept, really, that shouldn’t be overcomplicated.
VO2 “proper” is a variable that represents the “volume of oxygen (in liters or millileters) consumed over a period of time” at a specific intensity of exercise, whether that be measured by heart rate (HR) or wattage (W). As exercise intensity increases, VO2 increases in a proportional fashion. Once the body’s ability to consume a steadily increasing amount of oxygen has peaked, you now have VO2max. This point, historically, was thought to be a direct indication of what the body was capable of doing from an aerobic standpoint and served as a rev-limiter of sorts during highly intense exercise. We now know this to be otherwise…
SO, taking a pragmatic approach to discover (I use that word for a reason) what effects a change in VO2max would automatically mean that you understand what limits VO2max and/or what factors must be in place in order to achieve a higher VO2max.
Here’s where it starts getting interesting. See, oxygen delivery and consumption (in tandem) are the real constituents of VO2 and are solely responsible for the way it increases in response to a steadily increasing energy demand. Oxygen delivery is a complex series of exchanges which, at the cellular level, terminates in the formation of water, CO2, and most importantly, energy. It should be well-known to you that blood cells (RBC) serve as the primary vehicles that shuttle oxygen from the atmosphere down to the working muscles via a network of blood vessels. Once at the muscle, another transporter, myoglobin, accepts oxygen from RBCs and transports it into the cell where small organelles called “mitochondria” use it to make energy. Obviously the minutia of that little process is infinitely more complex, but you get the point. Basically, without this process, you have zero delivery of oxygen. If you have zero oxygen delivery, then you have a non-existent VO2max. So, rational thought would then dictate your next move- investigate a training structure that first increases the abundance of this machinery in your circulatory system/muscle tissue and then apply the precise stimulus in order to maximize it’s efficiency and function- this is how you increase your VO2max. More on this later…
So, then to the point, why is VO2max such a lousy way of determining a specific training adaptation? Simply put, your true VO2max doesn’t exist. It’s a hypothetical construct that can only be elucidated in relation to your high intensity. Of course if you wanted to argue, you could point me back to the graph I gave you just prior to making this argument where its easy to see that VO2 clearly peaks and then starts a short decent until the test is terminated. You could easily say that the highest point along the red line was the true VO2max, and you would be correct… kind of. I would then ask you a very simple question: “What makes that line reach a maximal point? Why, then, doesn’t it continue up forever?” The answer is this: That little line is simple a proxy, a representation, if you will, of the muscles’ ability to continue contracting and harvesting oxygen from the blood in proportion to exercise intensity despite a reduction in central drive (from the brain).
If you have a quick read of one of our recent and more smugly-titled blog entries, “The Importance of Breathing” you’ll recall that the muscles’ ability to continue contracting is a direct result of receiving neurological stimulation from the central nervous system (e.g brain). When exercising at high intensities, lactic acid clearance is the limiting factor for athletes operating near VO2max and serves as the metabolic governor to protect the vital tissues of the body. When the brain detects the threat of an acidic onslaught, it reacts by reducing the muscle’s ability to contract and thus keeping it from further contributing to the already overwhelming pool of lactic acid. This not only spares the brain permanent damage, as well as other vital tissues, it systematically limits your muscle’s continued harvest of oxygen from the blood, THUS peaking VO2. Now, what would have happened if your body’s high intensity defense mechanisms (e.g. the biochemical equipment that makes you more resilient to low intra-vascular pHs) were a little stronger? The answer: You would be able to continue buffering lactic acid, thus keeping the brain happy and sending signals to the muscle to continue contracting. This process would allow you to continue consuming oxygen even at a much higher energy demand and would manifest in a higher VO2max.
The question I as you next would be this: “Does then, VO2max have anything to do with your body’s overall ability to consume oxygen?” Well, yes and no. First of all, having a higher VO2max is impressive and does indicate that you are equipped with all the right machinery to consume oxygen. However, if your high intensity tolerance were better, you would be able to continue exercising at a higher level and thus producing a higher VO2max. It works a bit like the governor on a high-performance sports car. A Porche’ 911 Turbo is rated at 194mph, but if you were to govern the engine where only a small proportion of its power is realized, the top speed will only be theoretical not actual, just like VO2max. See, the only way to determine your true VO2max would require extraction of a small chunk of your muscle, called a muscle biopsy (which is just about as pleasant as slamming your fingers in a sliding glass door) and literally calculating the oxygen consuming capacity of the mitochondrial mass found within. This process is nearly as impossible as it is, well, impossible. So, when you participate in a “VO2max” test, and your peak VO2 is determined, it is only a theoretical value subjugated upon your current (and I say “current for a reason) abilities to regulate your blood acid chemistry. Because this ability is very easily influenced by exposure to high intensity exercise as well as only a few days of complete rest, your tolerance to high intensity exercise can very by as much as 12% in a few weeks – so will your VO2max.
Because your tolerance to high intensity is directly proportional to muscle activation and continued oxygen consumption, your VO2max is a PRODUCT of high intensity tolerance rather than an indicator of it.
Now, it is important to state in order to be scientific, the laboratory measurements that elucidate VO2max, while theoretical in nature, are still the best thing we have to determine overall oxygen consumption and aerobic response to training. But, basing your entire training season around VO2max or using it as anything other than a simple metric in conjunction with important metabolic markers such as MEP (metabolic equivalent point), anaerobic threshold, and ventilatory threshold, is a horrible move. There is a much better and more efficient way to gauge the effectiveness of your training. Anaerobic Threshold (AT) remains to be the most influential limiter of endurance performance. Because continual lactic acid buildup will result in an eventual deactivation of muscle tissue via the central nervous system and pathways mentioned just above, delaying the onset of lactic acid accumulation is the single most advantageous and all-inclusive approach to training an endurance athlete can adopt.
In closing, while VO2max is definitely a strong indicator of overall aerobic fitness, and we have known this for quite some time, it, like all other performance metrics, has limitations. The point of all this quite simple. It is critical that athletes pay specific attention to the key metabolic markers that are directly linked to an athlete’s fuel economy rather than VO2max alone. Determining proper training intensities using anaerobic threshold, metabolic equivalent point, and maximal fat oxidation rates (ALL of which can be determined via the same channels as VO2max), allows for a much more advantageous strategy in improving overall aerobic response making you a much better, more efficient athlete. These true indicators of fitness, when used in concert, solidify the foundation of what truly establishes the framework of what makes you a successful endurance athlete.