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What is Garmin really measuring when they give you a VO2 Max number?

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What is Garmin really measuring when they give you a VO2 Max number?

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Old 09-06-17, 01:53 PM
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FlashBazbo
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What is Garmin really measuring when they give you a VO2 Max number?

Occasionally, after a ride, my Garmin 820 will pop up a screen that gives me a "VO2 Max" number. (And they are quite impressive, I might add.) Clearly, since I'm not hooked up to a device that collects and analyzes my exhaled air, it's not a real VO2 Max test. Upon what is Garmin basing their "VO2 Max" number?
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Old 09-06-17, 01:57 PM
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20m power * 10.8 / weight - 7 + 400 hamers
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Old 09-06-17, 01:59 PM
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I don't think their calculation is public.
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Old 09-06-17, 02:04 PM
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Originally Posted by PepeM View Post
I don't think their calculation is public.
You're probably right. I can't find it anywhere. My number always seems too high, so I wanted to pick apart the formula / assumptions to see just how "too high" it really is.
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Old 09-06-17, 02:05 PM
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The other annoying mystery number is the physiological status, or some such, screen that pops up about 1.5 miles into a ride. What does that mean? If it's just a placebo, I need to find a place to disable it. It always shows me to be in very poor shape on race days.
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Old 09-06-17, 02:16 PM
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Yup probably as worthless as their calories burned calculation that goes simply by speed (or used to...) and time.
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Old 09-06-17, 02:18 PM
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Originally Posted by Grasschopper View Post
Yup probably as worthless as their calories burned calculation that goes simply by speed (or used to...) and time.
On "calories burned," in recent years I've noticed a close correlation between the "calories burned" number and the feet of climb. The numbers are often within 25 or 30 of each other.
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Old 09-06-17, 03:00 PM
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Garmin is of course "vanity sizing" the numbers. Duh.
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Old 09-06-17, 03:00 PM
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It's measuring the relationship between your power output and heart rate. This feature is in many Garmin units, but the software is done by a company called Firstbeat. They claim it has a 95 % correlation to a lab test, and that claim seems to be pretty widely accepted.

Firstbeat has a white paper about it on their site, but it describes the way they do it for running, and doesn't go into detail for cycling.

Originally Posted by FlashBazbo View Post
Occasionally, after a ride, my Garmin 820 will pop up a screen that gives me a "VO2 Max" number. (And they are quite impressive, I might add.) Clearly, since I'm not hooked up to a device that collects and analyzes my exhaled air, it's not a real VO2 Max test. Upon what is Garmin basing their "VO2 Max" number?
It calculates your VO2max every ride, as long as you have power, heart rate, and probably ride for at least 20 minutes. It only shows you the number when it's higher than you've scored in the past. That's why you only see it occasionally, and why it's always quite impressive. You can see the score after any ride though.
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Old 09-06-17, 03:03 PM
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Originally Posted by FlashBazbo View Post
The other annoying mystery number is the physiological status, or some such, screen that pops up about 1.5 miles into a ride. What does that mean? If it's just a placebo, I need to find a place to disable it. It always shows me to be in very poor shape on race days.
I don't know how long it takes you to go the first 1.5 miles, but if this comes up after ~12 minutes, it's your "Performance Condition" which is based on the variance in timing between individual heart beats, and on your PWR:HR relationship as it compares to your normal. Do you taper off before a race?
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Old 09-06-17, 03:04 PM
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Originally Posted by FlashBazbo View Post
On "calories burned," in recent years I've noticed a close correlation between the "calories burned" number and the feet of climb. The numbers are often within 25 or 30 of each other.
A lot of rides, my total kilo-Jules / calories for a ride and my feet of elevation gain are pretty close to each other. Then, a lot of rides, they're nowhere near. But it happens enough that I noticed it, too. (And my calories burned is coming from a power meter.)
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Old 09-06-17, 03:11 PM
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Originally Posted by Seattle Forrest View Post
It's measuring the relationship between your power output and heart rate. This feature is in many Garmin units, but the software is done by a company called Firstbeat. They claim it has a 95 % correlation to a lab test, and that claim seems to be pretty widely accepted.
I forgot to say your max heart rate has to be entered correctly for this feature to work. You pump more blood at maxHR than any other HR.
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Old 09-06-17, 03:12 PM
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Just like Calories burned and a lot of other numbers you get from these gadgets, they are estimates based on assumptions. Quite scientific, but science can not always give us an absolute number when certain data is missing.

So while they are useful to see trends, they should not be taken as absolute.
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Old 09-06-17, 03:17 PM
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Originally Posted by Seattle Forrest View Post
I don't know how long it takes you to go the first 1.5 miles, but if this comes up after ~12 minutes, it's your "Performance Condition" which is based on the variance in timing between individual heart beats, and on your PWR:HR relationship as it compares to your normal. Do you taper off before a race?
Since I'm warming up, it takes about 5 or 6 minutes to go that first 1.5 miles. But you got the screen right. It's the "Performance Condition."

Yes, I taper before a race. It's an easy week. And my "Performance Condition" before the race is usually negative. (But after any other rest day, it's usually very positive.) Could it be a result of pre-race adrenaline?

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Old 09-06-17, 03:22 PM
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Originally Posted by Seattle Forrest View Post
It calculates your VO2max every ride, as long as you have power, heart rate, and probably ride for at least 20 minutes. It only shows you the number when it's higher than you've scored in the past. That's why you only see it occasionally, and why it's always quite impressive. You can see the score after any ride though.
It's also impressive because it's generally between 10% and 15% higher than the 95th percentile value for geezers in my age range. (And my max HR is a lab tested, lets-see-if-we-can-self-induce-a-heart-attack value.)
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Old 09-06-17, 03:41 PM
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Originally Posted by FlashBazbo View Post
Since I'm warming up, it takes about 5 or 6 minutes to go that first 1.5 miles. But you got the screen right. It's the "Performance Condition."

Yes, I taper before a race. It's an easy week. And my "Performance Condition" before the race is usually negative. (But after any other rest day, it's usually very positive.) Could it be a result of pre-race adrenaline?
Is this a new 1030? Or a new unit at all? Garmins take a week or two to "get to know you" because the algorithms have a parameter for your exercise history.

I'd expect your PC to be positive on race day, because of the adrenaline and because you got rid of all the fatigue from regular training. Are you pacing yourself to avoid blowing up?

I don't know how your Edge shows this feature, my watch gives me a word and a number, like "poor" and -10 or whatever. Apparently that number is how you're doing in that moment compared to your VO2max, but that might not really be true. It changes over the course of a ride, if you look at the data in Connect instead of Strava you'll see a chart of performance condition just like elevation and speed and everything else.

I bet you can turn it off, or at least the popup notification.

(For what it's worth, I've never worked for Garmin and don't have any special insight into their code. I'm just a curious and analytical kind of guy who did a lot of reading recently before deciding whether to spend a boat load of money on one of their watches.)
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Old 09-06-17, 03:47 PM
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No, this is a Garmin 820 that knows me well. Probably 5,000 miles on it.

I pace myself using power. I pretty well know what power numbers I can do for an hour (FTP) and for 20 minutes (FTP test number) and other durations. But, of course, the PC number comes up during my warmup -- before the race. I'm not tired yet. I haven't really started.

I didn't know Connect had a chart for Performance Condition. I will have to check that out.
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Old 09-07-17, 06:13 AM
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Its giving people who are motivated by numbers, some numbers to with which to be motivated.
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Old 09-07-17, 07:09 AM
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Originally Posted by Seattle Forrest View Post
It's measuring the relationship between your power output and heart rate. This feature is in many Garmin units, but the software is done by a company called Firstbeat. They claim it has a 95 % correlation to a lab test, and that claim seems to be pretty widely accepted.

Firstbeat has a white paper about it on their site, but it describes the way they do it for running, and doesn't go into detail for cycling.



It calculates your VO2max every ride, as long as you have power, heart rate, and probably ride for at least 20 minutes. It only shows you the number when it's higher than you've scored in the past. That's why you only see it occasionally, and why it's always quite impressive. You can see the score after any ride though.
and weight
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Old 09-07-17, 08:19 AM
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It's just power, heart rate, and mysterious algorithms. I can continually bump up my Garmin VO2max by doing very hard efforts followed by a "recovery" day, where I physically cannot elevate my heart rate because I'm fatigued. My power output will be the same, but I will have a HR way down in Z1 for the entire ride, so my Garmin suddenly thinks I'm some kind of superman that can produce 2.5W/bpm all the time.

The Recovery Advisor pops up at 12 minutes on the dot. And it always, always says okay for me, even when I'm riding the day after a double metric. I saw it once light up yellow when I rode two times in one day. But even when the advisor at the end of a ride say something nutty like 48-60 hours reovery and I ride the next morning, it's still that green ring with OKAY in the middle.
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Old 09-07-17, 09:35 AM
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^^ And there you go. Thank you for actually paying attention and kinda reverse engineering whats going on.... and sharing it
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Old 09-07-17, 10:36 AM
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Originally Posted by DrIsotope View Post
It's just power, heart rate, and mysterious algorithms. I can continually bump up my Garmin VO2max by doing very hard efforts followed by a "recovery" day, where I physically cannot elevate my heart rate because I'm fatigued. My power output will be the same, but I will have a HR way down in Z1 for the entire ride, so my Garmin suddenly thinks I'm some kind of superman that can produce 2.5W/bpm all the time.
Interesting to read. My VO2max almost always falls on really hard efforts, or at the end of several tough days. When I'm heavily fatigued, the number drops a point or two, and then it comes back in a few days after I recover. I never looked very closely at the data to see why, I just accepted that it's a short-term thing, like how a trail run kills my running VO2max until I get back on pavement.

Originally Posted by DrIsotope View Post
The Recovery Advisor pops up at 12 minutes on the dot. And it always, always says okay for me, even when I'm riding the day after a double metric. I saw it once light up yellow when I rode two times in one day. But even when the advisor at the end of a ride say something nutty like 48-60 hours reovery and I ride the next morning, it's still that green ring with OKAY in the middle.
Mine is almost always at 12 minutes, too. Supposedly it can take anywhere from 6 to 20, and pops up whenever the thing has enough HRV data to crunch.

Mine is all over the board from poor to good, and generally seems pretty realistic. There have been days where it says good and I feel like crap, but push through and perform pretty well and even feel better for it.

A lot of the time, a bike ride gives me a recovery estimate of 30+ hours. I think that's too much. A run that puts more training load on my cardiovascular system gives me a recovery estimate of 20 hours. And that seems realistic.

Recovery of < 24 hours means "train as normal." It's not how long you should wait before your next ride, it's how long you'd need before a complete recovery, like for a race.
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Old 09-07-17, 10:41 AM
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I did a metric century with my wife, and was non-stop Z1 all day. My recovery advisor time was 5 hours.

I guess I just have so many rides in, with HRM data on every single one of them, that it's dead-on 12 minutes. Some days I like to race the Recovery Advisor, and see how far I can get in that first 12 minutes. It's wildly counterproductive.
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Old 09-07-17, 10:43 AM
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...intelligence ?
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Old 09-07-17, 02:20 PM
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Sounds like it's based strictly on heart rate, see https://www.firstbeat.com/app/upload...1-11-20142.pdf & https://www.firstbeat.com/app/upload...estimation.pdf. Wish they add the option for power, VO2 (L/min) = 0.0108 x power (W) + 0.007 x body mass (kg). I get my estimate from Golden Cheetah.
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