Chris Newport, an exercise physiologist, breaks down how Garmin VO2 max estimates work and why they're approximations. He walks through the math using ACSM equations: a 10-minute mile equals roughly 35.7 ml/kg/min, a 6-minute mile about 57.1. Device predictions vary by sport and differ from lab tests, so don't obsess over the number.
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I am your host, Coach Chris Newport. And one thing that I get asked all the time in our exercise physiology lab is, is my Garmin or is my watch correct in its VO2 max calculator? Now, while I don't know what all the equations that some of these devices use, what I do know is that there are simple ways to be able to predict what your VO2 is based on a certain amount of work you're doing. So if you're watching this on YouTube or if you head over to our website, I've created a VO2 calculator. So keep in mind there's a couple of things to remember when it comes to volume of oxygen. VO2 is volume of oxygen. We like to think of VO2 max because that's the maximum amount of oxygen that you can take in and use for work, but there's a necessity for VO2 no matter what you're doing. So if you're at rest, you typically need about 3.5 as your volume of oxygen, plus or minus a little bit, depends on your size. But that's where actually testing it becomes so important to get the more accurate representation. But then we also have a VO2 for things like walking, for things like running, which those two will change even at the same paces. So walking at one pace is a lower metabolic cost and uses less VO2 than running at the same pace. Cycling, we got the same kind of thing. So if you were to come into my lab and I wanted to create the appropriate protocol for you based on your current fitness level to be able to best determine what your max is, and then of course zones and all those other things, I would need to know what is the prediction on your watch just for fun. And then also what is a pace that you can go at all day and what is a pace that feels really hard? And then we fit the protocol in for that. Now I have a cheat sheet. I'm not showing you this cheat sheet necessarily right now, but it's a very easy way to basically use this calculator. And I've created a spreadsheet and I've got it at the, our lab. And we look at, okay, this person has done a 5K at this particular pace, which means that volume of oxygen is X number. Therefore they can probably go faster than that. So let's use an example. Let's say somebody is running and they're going to be doing, I don't know, so how about 6 miles per hour? That's a 10-minute mile at a 0% grade. We calculate the necessary VO2 for that, and that's 35.7. And the, uh, ACSM metabolic equations are down there. Now this is a great way to again predict what is the general amount of VO2 that you're going to need, but it's never going to be exactly right on. So let's play with this again. Let's say we're going to do 10 miles per hour, so a 6-minute mile. I'm going to calculate the VO2, and that's 57.1. So with your watch, it is trying to calculate how much activity are you doing, and then what is a rough percentage of what that is, of what you could be your max, or what could be something like a 5K. 'Cause it's gonna give you some of those predictions. We predict that based on your workouts that you've done, you could do a 25-minute 5K, a 15-minute 5K, whatever the case may be. So don't hold so much weight in what your VO2 max predictor is on your device. Of course, we see that VO2 max is one of the best, uh, longevity predictors. So it is nice. I like to think of it like a physical. If you can do it about once a year, that's a great thing to do. Also know that your VO2 max is going to vary sport to sport. So some of you triathletes out there might see that you have a prediction for your run and you have a prediction for your bike. Totally normal. And maybe that's also an opportunity for you to improve one sport over the other. So again, don't hold too, too much weight in what your device says in terms of your VO2 max. I also get people who are telling me, "Oh, my watch says that my VO2 max went down," and that depresses them. Turn that feature off, y'all. Like, you should not feel depressed about your fitness level. But also know that whatever you do, there is a metabolic cost. Whether you are walking, whether you are sitting, whether you are sleeping, whether you are sprinting, whether you are running. And that of course translates to calorie expenditure too. So keep that in mind. But VO2 is all about how much oxygen do you need to take that oxygen and send it to working muscles so that you can do work. But at the end of the day, it's your training that is going to improve not only your overall VO2 max, but your economy, So how can you be super efficient and actually use a little less VO2 for any given pace? And that goes along with appropriate form work, with appropriate strength training, with good nutrition and things that are going to support your body in this quest of improving your fitness and not just your VO2 max. So if you wanna head over to our website, and play with this calculator, you can make a couple of predictions and be like, okay, well I know, 'cause we've had some folks lately who've been able to get up to 12 miles per hour or faster, their estimated, uh, VO2 is in the 60s. But when you actually come into the lab, that's when we see, okay, the prediction might be 67, but your actual VO2 max might be 60, might be 62. So at least it gives us as testers a, more specific idea of where your fitness level might be at so that we can determine the appropriate protocol and you can not be overly fatigued during your test. So hopefully that gave you a little bit of extra information on whether your device is correct, whether you should pay attention to it, and what is VO2, and then what is VO2 max, and how should it matter to you. So hopefully that was just a little, little bite-size piece of fun information based on your fitness level. And if you have more questions about these things, send us a message. I wanna hear about them so that we can put more good information out to help you be more awesome. Thanks for listening, and we will catch you next time.
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