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Exercise Physiology for Beginners
Written by Dr. SkibaAs a physician specializing in Sports Medicine, I make my daily bread by applying scientific principles to the ailments of my patients. For instance, knowing what sorts of antibiotics kill particular bacteria permits me to effectively treat swimmer’s ear. In a like manner, understanding physiology allows me to make inferences about the underlying fitness of the athletes I consult with, and thereby permits me to make very specific recommendations regarding the types of training each athlete needs.
Words like “science” and “physiology” often frighten athletes. These terms conjure memories of complicated equations; mental images of a fellow like me asking them inane questions as their secondary school classmates quietly snicker behind them. It doesn’t need to be this way. The truth is that most of the physiology you ought to understand as an athlete is no more complicated than grade school biology. This article is going to help you to make sense of some of those words you seen thrown around in magazines and on the Internet.
To start with, there are three terms that I’d like you to be comfortable with. These are VO2, LT, and efficiency/economy. (Okay, I guess that is 4 terms, but the last 2 are often used interchangeably). We will begin with VO2.
VO2 stands for Volume of 02 (oxygen). It is a measurement (in milliliters or liters) of how much oxygen your body is using to do something. When you are eating crisps and watching the soccer match, it is quite low. When you are jumping up and down and swearing at the referee, it is a bit higher. When you are running and ducking missiles being hurled by an enraged spouse who is fed up with your soccer obsession, it is quite high. VO2max is the maximum amount of oxygen you can use. You reach this point during exhaustive exercise that you can maintain for perhaps 5 to 10 minutes.
With regard to VO2max, higher is better. The ability to use more oxygen means you are capable of doing more work and going faster. It is largely determined by genetics, however, it is possible to raise VO2max by up to 60% in untrained people, with 15-30% being more typical. These gains are mostly realized within the first 2 months of training, though modest improvements may continue to occur over longer periods. Anatomically speaking, VO2max is largely determined by the maximal pumping capacity of the heart. To a lesser extent, in very well trained athletes, it is likely also determined by how many capillaries are present in the muscles. The most important thing to remember is that the muscles will use as much oxygen as you can send them. Thus, attempting to improve VO2 should be an important part of any endurance athletes training regimen.
Now, let’s talk about Lactate Threshold (LT). Any time you exercise, you use both fat and carbohydrate for fuel. As you travel faster and faster, you switch your fuel mix to include relatively more carbohydrate, and relatively less fat. The byproduct of burning that carbohydrate is lactate. Thus, lactate makes a nice marker for exercise intensity. The point at which you make enough lactate to raise the blood level by 1 milimole is called Lactate Threshold. Very well trained athletes can go quite hard before they reach LT, whereas mere mortals like myself reach it at more pedestrian paces. Power output / pace at LT is perhaps the most trainable of the directly-measured physiologic parameters: athletes may continue to improve over a period of many years.
Now, let’s discuss what lactate and LT aren’t. First of all, LT has nothing to do with how “aerobic” or “anaerobic” you are. This is an antiquated notion that has been soundly debunked. Again, the fuel mix discussed earlier largely determines it. Further, lactate is not a “waste product”; it turns out to be a high energy chemical in it’s own right, and is in fact used as fuel by the heart and kidneys, as well as other muscle cells! Finally, lactate is most likely not related to the “burn” you feel during hard exercise. It is just an innocent bystander.
Finally, we come to the terms efficiency and economy. These words are often used rather carelessly. Runners are referred to as “efficient”, for instance. However, in the realm of physiology, efficiency refers to only one thing: how much oxygen the body requires to do a particular task. For instance, if two cyclists of similar size are pedaling side by side on stationary bikes at a power output of 200 watts, but one of them uses less oxygen to do the job, we say this cyclist is more efficient. In the same way, we can say that two runners of the same size running at the same speed may be differentiated by which is using less oxygen. This athlete is said to be more economical. The reason we use the word efficiency for cycling is that we can directly measure the power output. We use the word economy for running because it is much more difficult to measure the precise power output of a runner. Thus, the engineering term efficiency would not be properly used in that context.
This discussion of efficiency and economy has an important consequence. Since we cannot actually calculate efficiency or economy without measuring oxygen use, it nonsensical to look at a runner or cyclist and claim one is more “efficient” than the other. One may have a “better looking” stride than another, but it does not necessarily mean they use any more or less oxygen to run than anyone else. Put another way, Paula Radcliffe may run like a bobblehead, but given her physiologic characteristics as measured in the laboratory (not to mention her world records), you’d be hard pressed to say she was inefficient.
At this point, the question you should be asking is, “What does any of this have to do with my training?” By understanding these principles, we can make logical inferences about what kinds of training will improve the physiologic parameters we have discussed. Next week, we will discuss how particular workouts can affect each of these systems, and how they will improve your times on race day.
