FAQ regarding Metabolic and VO2 testing
Why should I perform an Exercise Metabolic (VO2) Test?
What is an Exercise Metabolic Test or VO2 test?
What exactly is measured in an Exercise Metabolic Test?
How is my physiological data gathered?
So what do all those measurements tell me?
How often should I do an Exercise Metabolic Test?
When can I do an Exercise Metabolic Test?
How high should my fitness level be before I do an Exercise Metabolic Test?
How does an Exercise Metabolic Test help me manage my weight?
Shouldn’t I do a VO2 “Max” test?
How long does an Exercise Metabolic Test take?
What is Anaerobic Threshold, and how is it different than Lactate Threshold?
Why is Fat Burning so important?
Why not just rely on Carbohydrate or Glucose as my fuel source?
Can I use test results from one sport, like cycling, and use it for another, like running?
What’s wrong with using training zones based on my Estimated Max Heart Rate?
I’m not an athlete, I just exercise for fun or fitness, so this testing is irrelevant, right?
Download a PDF of this information: V02 FAQ (pdf 289 kb)
Q: Why should I perform an Exercise Metabolic (VO2) Test?
A: This test reveals your body’s unique response to physical stress at different levels of intensity. It will give you information to tailor exercise and training parameters (intensity, duration, frequency) to help you avoid over training or under training, which also helps you avoid physical injury due to training errors. This test is also an excellent tool to gain information to help with nutritional strategies for weight management and replenishment during exercise, training or racing.
Q: What is an Exercise Metabolic Test or VO2 test?
A: In this sense, an Exercise Metabolic Test is an analysis of some key components of your metabolism starting in a resting state, and gradually progressing to a state of higher exercise intensity. By using a technique called Indirect Calorimetry, this test reveals how many calories a person burns per minute while exercising, and how many of those calories are drawn from fat versus carbohydrates, and more importantly, how aerobically efficient an athlete is at different levels of exercise intensity. VO2 is merely a measurement of the volume of oxygen that a person is able to take in and utilize in their body. VO2 is just one of measurements taken in an Exercise Metabolic Test. We use the phrase “Active or Exercise Metabolic Test” because it is a more accurate term indicating that this test measures much more than just VO2, although we sometimes refer to it as a VO2 test simply because it is more well known by that name.
Q: What exactly is measured in an Exercise Metabolic Test?
A: The physiological measurements recorded include your VO2, VCO2 (volume of carbon dioxide exhaled), and your heart rate. These samplings are taken every few seconds so we can see exactly what your metabolism is doing at any given exercise intensity. Other data is recorded at the same time depending on the mode of testing. If you test on a bicycle then the resistance load is recorded in the form of watts (power). If the test is done on a treadmill then the speed and incline of the treadmill are recorded.
Q: How is my physiological data gathered?
A: After an ambient air sample is tested to calibrate the gas analyzer, your O2 and CO2 data are measured through samples taken every few seconds as you breathe through a mask that covers your nose and mouth, connected by small tubes to the analyzer. Heart rate is recorded by telemetry (wireless transmission) from a transmitter strap worn around your chest, and received by a sensor “snake” also attached to the analyzer.
Q: So what do all those measurements tell me?
A: They might not mean anything useful to you, however we go through this data with you, explain it, and make sure that you walk away with information that you can immediately apply to your exercise, training, or racing activities. Some very important items that we go over are your; Aerobic Base, Aerobic Profile, Anaerobic Threshold, Peak VO2 or VO2max, Training Zones based on your results, and Fuel Mixture (fat vs. carbohydrate) at different exercise intensities. The data that we interpret for you will be dependent on your goals and needs. Some athletes have enough knowledge, or access to a coach or trainer, that they can use this data without needing our interpretation. If you are new to this kind of information then you should consider also scheduling an Exercise Consultation or Coaching Set-Up in conjunction with your test.
Q: How often should I do an Exercise Metabolic Test?
A: Retesting is dependent entirely on your goals and resources. A person using this test to find the best exercise parameters simply to burn the most fat for weight management may want to do the test just once and use their resulting Customized Training Zones indefinitely. It is not uncommon for elite athletes to test on a weekly basis during key periods of their training. Athletes who are very serious about tailoring their training to meet their current abilities and needs may test at the end of every Mesocycle in their training plan, for example: A common training plan for endurance athletes is to have a four week cycle composed of three weeks of increasing training load followed by a relative rest week. Testing at the end of every rest week ensures that the athlete is indeed ready to enter into the next progression of workload for the next cycle, or the test may reveal that they would benefit more from continued training at a lower workload. Another strategy is to test just before changing your training plan focus, such as moving from a Base phase to a Build phase, again to ensure that your body is ready to deal with a more stressful workload. Repeat testing is a great way to objectively measure improvements made by previous training, and give guidance for future training.
Q: When can I do an Exercise Metabolic Test?
A: You can do the test anytime, however while certain conditions may make for interesting results, we suggest following certain guidelines that will result in the most useful test results. As mentioned before, an ideal time to test is at the end of a “rest week” in your training cycle. To get an accurate test, the athlete should be relatively rested, meaning completely recovered from any big events, relatively recovered from your current training, minimal or no exercise the day before the test, and no exercise during the same day before the test. The athlete should be healthy and recovered from any colds or illnesses. We discourage eating for four hours before the test, with the possible exception of a small amount of easily digested foods up to two hours before the test.
Q: How high should my fitness level be before I do an Exercise Metabolic Test?
A: There is no level of fitness that needs to be attained in order to do the test. Some people think they need to “get in shape” before performing the test, when in fact they are probably better off testing before getting in shape so that they have optimal training parameters to help them spend their training time as efficiently as possible. The primary purpose of the test is to provide you with information to make your training as efficient as possible, not to impress anyone with your test “score.” The most important time to test is when first getting into shape, or conducting Base training, to ensure that the training parameters being used are accurate. It would be unfortunate to do three months of Base training only to then perform the test and discover that your have wasted that time training with the wrong exercise parameters.
Q: How does an Exercise Metabolic Test help me manage my weight?
A: The test will show you how many calories you burn at different intensities (Zones), and how many of those calories come from the metabolism of fat. This helps in determining a more accurate balance of daily caloric intake. Achieving a small deficit in daily caloric intake through a combination of diet and exercise has been repeatedly proven to be the best way to achieve healthy and long-lasting weight loss with improved body composition. For athletes with a very high training volume this information will help them tailor their diet to ensure that they are getting adequate daily nutrition to meet the demands put on their bodies. A “Resting Metabolic Rate” test can also be done to get a more accurate picture of how many calories your body burns during a normal day, not including exercise time. Combining the EMR and RMR tests are ideal for anyone concerned about daily caloric intake.
Q: What kind of equipment do you use?
A: We use the New Leaf system produced by the Medgraphics Company. This is the same system that is used by hospitals, Olympic Training Centers, and sports performance centers. Cycling tests are conducted on your own bike, connected to our Slocum trainer stand, with a customized, ramped wattage protocol programmed through our Computrainer system. Tests for running, walking, and hiking/mountaineering are conducted on our treadmill with protocols using systematic increases in speed and incline appropriate to your ability and activity.
A: The mask is made of neoprene and is handwashable and reusable, but for sanitary reasons we do not reuse masks and require that people supply their own mask. We do sell the masks for $40. You can borrow a friend’s mask if you desire, but keep in mind that during the test they will become saturated with sweat and saliva. The mask is required for both the Resting and Exercise Metabolic Tests. We also encourage people to obtain a mask in advance of the test, and actually do a bit of exercise with it, so that they can become accustomed to wearing it. Occasionally an athlete will experience some anxiety when they first don the mask and begin breathing harder during exercise. This usually diminishes as the test progresses, but if you are prone to anxiety or claustrophobia then you should definitely get some practice exercising with the mask on before testing.
Q: Shouldn’t I do a VO2 “Max” test?
A: You can do a VO2max test if you have no contraindications for it, however we do not encourage it for most of our clients. There are several reasons why. VO2max is simply the absolute maximum amount of oxygen that your body can take in and utilize. While it can be altered through training, it is largely genetically predetermined. For the vast majority of people, your VO2max number is irrelevant for practical purposes. While it is interesting to compare with the VO2max numbers of famous athletes and may provide bragging rights among your friends, it vary rarely has any bearing on how you should conduct your training. Characteristics of your Aerobic Profile and your Anaerobic Threshold are much more critical in predicting endurance performance and dictating current training parameters. An athlete that has been training consistently at a relatively high level, is in good health, and participates in an activity that may be affected by VO2max is a good candidate to undergo this kind of test. It is also worth mentioning that a VO2max test is physically very painful and requires a unique mental ability to perform despite extreme physical discomfort. Some athletes that attempt VO2max never actually achieve it due to a lack of motivation or ability to tolerate the discomfort. The standard Exercise Metabolic Test will show your VO2 at Anaerobic Threshold and your Peak VO2, which is simply the highest VO2 achieved during the test.
Q: How long does an Exercise Metabolic Test take?
A: We schedule an hour for the basic test with pertinent interpretation. We try to achieve Anaerobic Threshold within 8-12 minutes of physical work, and a VO2max test will likely take longer.
Q: What is Anaerobic Threshold, and how is it different than Lactate Threshold?
A: Anaerobic Threshold (AT) refers to a high level of exercise intensity where your body can no longer rely on utilizing fat and oxygen in the aerobic metabolism to meet its energy demands. There are many names for this physiological landmark, including Lactate Threshold (LT). A full explanation would be too lengthy for the purposes of this FAQ, but basically the exercise intensity at which AT occurs is the same point at which lactate production becomes greater than lactate recycling, causing a buildup of lactate in the blood. Blood lactate testing can be done to find this point and is often a cheaper lab test to find AT or LT, but involves frequent blood sampling throughout the test, only a fraction of data points, and no Aerobic Profile. An athlete’s Aerobic profile and AT characteristics are by far the most important information to have for training and racing. These physiological characteristics are the best predictors of endurance performance, and should dictate training parameters. We start creating Custom Training Zones based on Joe Friel’s concept of using percentages of Heart Rate at AT to determine Training Zones, but then we also look at your Aerobic Profile and other data to possibly make further alterations to your custom zones.
Q: What is an “Aerobic Profile”?
A: An aerobic profile is a graphical snapshot using objective data that depicts how efficiently your body utilizes fat and oxygen as fuel from the time your body goes aerobic (very light exercise) until it goes anaerobic (high intensity exercise). This is graphed out for you overlaid with your custom Training Zones. In each Zone your calorie and fat burning abilities are noted, and we can see where exactly you are weak aerobically. Deficits in Aerobic Base can easily be seen, as well as in any other training or racing zone.
Q: Why is Fat Burning so important?
A: An analysis of your fat burning metabolic characteristics is important for several reasons. As previously mentioned, we can find the precise heart rate at which you burn the most fat, and it is usually at a lower exercise intensity than most people expect. Fat and oxygen are used together in direct proportion during aerobic metabolism, so by measuring how much fat is being used, we can determine how aerobically efficient an athlete is at any exercise intensity. For any kind of endurance activity, being aerobically efficient at lower intensities is an absolute must, especially before increasing training intensity to higher levels, this is commonly referred to as having a good Aerobic Base. Gram for gram, fat supplies a much larger quantity of energy than carhobohydrates, and we all have a relatively unlimited supply of it stored away in our bodies, so for endurance athletes it is without a doubt the fuel of choice. The problem with fat as a fuel source is that the metabolic process required to break down fat into components that can be used by muscle cells is relatively long and complex. It is much easier for our bodies to use this process during relatively light levels of activity, which are commonly called Fat Burning Zones. At the same time fat is being burned, carbohydrate is also being used for energy. The two fuel sources are always being utilized at the same time, so the crux of the fuel issue is which one is being used as the predominant source of fuel. Once we know how your body utilizes fat, we can determine training parameters to teach your body to use fat at higher and higher intensities. As aerobic intensity increases, your ability to use fat will decrease, and the utilization of carbohydrate will increase, until it becomes the predominant fuel source. This physiological landmark is sometimes called an Aerobic Baseline or Crossover Point, and is also very important in determining endurance performance.
Q: Why not just rely on Carbohydrate or Glucose as my fuel source?
A: Carbohydrate is used as fuel by muscle cells in the form of blood glucose, and has a very limited supply. We keep reserves of Glycogen in muscle and liver tissue that can be tapped for conversion to blood glucose, but it is also a limited supply, so if we are exercising or racing at an intensity that utilizes carbohydrate as the predominant fuel source, we will run out of fuel and “bonk,” or “hit the wall.” One of the graphs produced by the Exercise Metabolic Test shows exactly how much fat and carbohydrate are being utilized at any given exercise intensity, and where your Crossover point is. Understanding how your body utilizes fat versus carbohydrate is also important in making fueling decisions for training or racing, and may dictate the best maximum aerobic intensity that an athlete can sustain for a given endurance event.
Q: Can I use test results from one sport, like cycling, and use it for another, like running?
A: While there are some general patterns of how the metabolic demands of one sport relate to another, we don’t suggest using test results from one sport for training in another. For example; If an athlete is equally economical and has an equal training history and experience in running and cycling, we know that on average a running AT will be around ten beats per minute higher than a cycling AT. This is a rough generalization relating ATs, and does not at all address an aerobic profile. An athlete can have identical running and cycling ATs, but have Aerobic Profiles so drastically different between that they would need to train at very different intensities, or Zones, in one sport versus the other.
Q: What’s wrong with using training zones based on my Estimated Max Heart Rate?
A: There are two big problems with using training zones based on Estimated Max Heart Rate. Estimated physiological parameters relating to heart rate, thresholds or VO2 are notoriously inaccurate. I estimate that only about 5% of the people we test actually fall within the estimated norms. The second problem with training zones based on Max Heart Rate or VO2max is that, as mentioned earlier, these “max” numbers, even if accurate, are irrelevant for training and racing. The characteristics of your Anaerobic Threshold and your Aerobic Profile will dictate your endurance performance, and should dictate your training parameters.
Q: I’m not an athlete, I just exercise for fun or fitness, so this testing is irrelevant, right?
A: Wrong. You are an athlete, and it is relevant. One of my favorite quotes that defines who qualifies as an athlete is “anyone with a body” that uses it. If you are physically active and exercising, ask yourself why. If it is to train for something then we have stated our case for relevance repeatedly already. If you are just trying to get or stay fit and healthy then this testing will show you the most efficient training parameters to meet that goal and minimize your potential for injury or wasting exercise time.