Now we're going to talk about the VO2max test itself. In the lab, an athlete's VOmax is tested using a treadmill or a bicycle ergometer. Coaches typically don't use the lab VO2max test due to its expense. Instead they use the common sports specific field based test just as the bleep test that we just discussed. However, it's worth having some understanding of the lab test because the protocol for the field test are developed from day to obtained from the lab test as well understanding the lab VO2max test helps you understand the theory upon which the field tests are based. So here's a graphic of typical data gathered during a lab VO2max test. It includes heart rate, which is the blue line, carbon dioxide which is the green line and oxygen consumption which is the maroon line. The maximum VO2 consumption is the highest amount of oxygen the athlete's aerobic energy system is capable of using. And theoretically, athletes with a very high VO2max are able to produce more ATP than those with a lower VO2max, and can therefore run at a higher speed before exhaustion. When performing the lab VO2max test, the athlete is fitted with a mask that is attached by a hose to a device that's capable of measuring how much air the athlete is breathing each minute. It also measures the amount of carbon dioxide and oxygen that is in the exhaled air. The oxygen passes through the alveoli in the lungs and into the blood vessels that I have illustrated here. This area down here is representing the blood tissue the athlete is using. And the known amount of oxygen in the atmospheric air is 21%. And as the blood passes through the muscle cells, the oxygen needed by the mitochondria for the aerobic energy system is extracted and the carbon dioxide is deposited into the blood stream. The oxygen that's not needed remains in the blood stream and travels along with the carbon dioxide back to the lungs, where it is exhaled. The oxygen in the blood returning back to the lungs contains somewhat less than 21% oxygen depending on how much the athlete's muscles have used. We can gain some insight into how much oxygen the mitochondria extract by measuring the quantity of oxygen left in the exhaled air. Which is subtract the oxygen and the air remaining in the lungs from the 21% that entered into the lungs. We are also able to measure the amount of carbon dioxide produced by the cells from the same exhaled air. We know how much carbon dioxide was in the air when the athletes breathed in and how much is in there when the athlete breathes out. The hose that is in the athlete's mouth is connected to equipment that measures both oxygen and carbon dioxide that is in the expired air. So let's take a look at the athlete's oxygen consumption with increasing speed. So this line here represents the increasing oxygen consumption as the athlete increases speed every couple of minutes. When the athlete increases speed more muscle fibers are recruited, and therefore a higher quantity of oxygen is extracted from the blood to meet the mitochondrial needs of the muscle fibers. At some point, the ability of the mitochondria to use the oxygen reaches its upper limit. And the athlete is unable to increase speed any further. And this is the athlete's VO2max. At any point in time, the difference between the amount of oxygen entering the lungs and amount left in the lungs exhaled is referred to as the oxygen uptake, or VO2. Now the V just simply stands for volume and the peak amount of oxygen used is a really good indication of the athlete's endurance potential. It also tells us quite a bit about the health status of the athlete's aerobic energy system. We can also graph the carbon dioxide that is produced, as you see here in the green line. As the athlete moves faster more carbon dioxide is being produced. A carbon dioxide provides quite a bit of information but we're not going to talk about this for now. So let's get rid of the carbon dioxide curve. Besides oxygen and carbon dioxide, the athlete's heart rate is also monitored during the lab test. Having the heart rate data allows us to estimate the athlete's oxygen consumption when moving at different speeds. Theoretically, if you have heart rate and oxygen consumption, you can estimate the athlete's oxygen consumption by simply looking at their heart rate when they're training.
