Ever since I’ve gotten my Garmin Forerunner 945 (FR945), I’ve had a minor problem. Minor in that it basically doesn’t affect tracking for any of my training, but that one of the included Garmin Connect metrics doesn’t appear to be working properly (at all, really) because of it.
The FR945 comes with temperature and altimeter readers, which allows Connect to track Heat Acclimation and Altitude Acclimation using tech and code designed in conjunction with a company called Firstbeat.
The heat acclimation function works fine. Las Vegas becomes hell during the summer, and Connect has readily noted my high percentage of heat acclimation after many of my walks and runs in the 100°F+ heat. My calculated heat acclimation only dissipates to zero towards winter as the temperature finally dips and stays below 60°F.
However, the altitude acclimation hasn’t really worked as described. Garmin per their manuals tracks altitude acclimation at as low as 800 meters, 2620′.
The Vegas Valley metro area is a giant bowl surrounded by mountains that varies in altitude between about 1600′ and over 3000′ depending on where in the Valley you are.
I work in Summerlin near the western edge of town, and the altitude at my workplace is about 2720′, above the minimum measured threshold. I train nearby, and most of my running is in a neighborhood that sits between 3050′ and 3200′ in altitude. Any running I do in this area should (per Garmin’s description) count towards altitude acclimation, and most of my running is at this altitude.
I live and train on weekends at a lower 2300-2500′ on another end of town. I don’t expect this to count, but again most of my training by time/mileage/incidences/whatever you want to count is near work at the higher nominally eligible altitude.
However, other than after a long weekend trip to Flagstaff last May, Garmin has never shown I have any altitude acclimation. After the Flagstaff data wore off, my acclimation has always shown up as 0.
According to their documentation, however, all my tracked run training over 2620′ should have triggered an altitude acclimation reading. It’s not happening.
Is something broken? Are there other disqualifying parameters Garmin’s support materials do not spell out? I had no idea.
I’ve gone through (several times over) and made sure GPS, altimeter, and other tracking settings are set up exactly to the letter as the manuals have said they need to be set in order for altitude to be tracked. Same result. It’s not happening.
I have on multiple occasions over the last 6-9 months called and messaged and worked with Garmin Support many times trying to remedy this, wading through their usual “no, do the regular troubleshooting first because you’re probably just stupid” conversation and steps and then wading through toggling readers and settings with the watch (This unfortunately seems to be a common end user experience when dealing with Garmin Support, a somewhat separate, larger topic for later; myself and others have had general issues with Garmin’s pithy, sometimes hostile approach to end user support).
All attempts to get a more useful answer than “uh, we’re not sure, keep us posted” have been futile. Same result. It’s not happening.
Now… every other advertised feature on the watch works fine, as described. All of my workouts have been tracked just fine. It’s not like I spent $650 on a watch that doesn’t add any value over the cheaper ~$300 Forerunners.
But it is a metric I care enough about tracking that it’s quite bothersome that a watch designed to track altitude acclimation simply won’t track it despite my having checked all the effort/setting boxes, and despite multiple efforts to have Garmin Support troubleshoot it.
At some point in the last month I once again lived out the definition of insanity, and did what hadn’t worked before in hopes it would work this time. I went digging via Google Search for information on those who had issues with altitude tracking on their relevant Garmin watches.
The official Garmin staff responses to these questions on their forums is typically some pithy form of ‘look, the manual says this, just do what it says, we aren’t helping you further’. However, someone in some Support forum post that I’ve read but since forgotten linked this FAQ page on how it works, which has recently added (it wasn’t there six months ago) and spelled out a key (previously unseen) bit of info about the altitude acclimation function (boldface is mine for emphasis).
It works best if you have Wi-Fi enabled and the watch or cycling computer is in sleep mode. In this state, the watch or cycling computer will wake up overnight and check the living altitude level to ensure that it is accurate and up to date.
After discovering this, now I think I finally found the answer to why the FR doesn’t track my altitude acclimation from workouts. Nothing is broken. It’s working exactly the way it’s designed. And unfortunately, the fundamental design has created a logistical loophole that I’ve fallen into.
Without going into the mountain of research behind this, one accepted key to altitude acclimation is living and sleeping at the given altitude. Often the complication of acclimating to high altitude isn’t just the thinner air when you train, but having to try and live, sleep, recover, in that thinner air.
In the short run and possibly beyond, your sleep and recovery isn’t as sound when you’re at high altitude. You get less oxygen 24/7. Your body doesn’t recharge as well during sleep with less oxygen.
So by design Garmin’s relevant watches measure the altitude when you should be sleeping. After all, that’s the altitude you live in, by the algorithm designers’ general logic, right? That makes sense.
Even if you “train low, live high” as many elite athletes do (going downhill to train at lower oxygen-rich altitudes, then returning to higher ground and living there to improve your oxygen uptake ability)… the watch by design will check in at midnight, notice your higher altitude, and calculate that you’re acclimated to that higher altitude than which you trained.
However, then by design it wouldn’t account for individuals who do all their training at altitude, then live and sleep below the calculated altitude threshold. I mean, why would anyone do that as a form of altitude training? It’s not nearly as effective. Who would do such a thing?
Well, I do… not because I consider my approach some form of altitude training. I do it for practical reasons. Logistically that’s how my life is set up. I live in a region that’s generally at a higher altitude than most places to begin with, and incidentally work at a higher altitude than where I live, one that passes the Garmin/Firstbeat threshold.
It’s practical to do most of my training at that higher altitude, right after work, since my best option for a running course is right there and it’s a better place to run than back home.
But, because I sleep every night at 2350′, the algorithm by design presumes that since I live below its 2620′ threshold, I therefore cannot be altitude acclimated at all… even though 80-90% of my aerobic training by time/mileage/workouts per week is done at 2700′-3100′, within Garmin’s stated altitude tracking threshold.
If I lived and slept in the same altitude, the watch would eventually show I’m acclimated to about 3000′. Since I don’t sleep here (and with the average home in Summerlin being quite expensive, don’t hold your breath for that happening), none of the training I do here counts in Garmin and Firstbeat’s altitude acclimation algorithm. Once it checks on me at midnight and sees I’m at 2350′, the system decides that my calculated acclimation is actually zero.
So my Garmin Forerunner watch isn’t broken at all. Given how it’s designed, absolutely nothing is wrong with it.
However, the altitude acclimation algorithm and function’s design creates a loophole. If you train above the altitude threshold of 800 meters, but you sleep below 800 meters, then your training doesn’t produce any measured altitude acclimation.
Now, this is beyond where I’m willing to go with this post, and probably beyond Garmin’s scope as they and Firstbeat’s work on this tech is based on incumbent research, but… the threshold at which altitude acclimation’s measured here is mostly arbitrary. Garmin and Firstbeat devs had to pick a starting point and stick to it, sure. If known incumbent research (and any resulting hasty, commonly accepted conclusions) indicates that’s the proper threshold, they are going to go with the accepted premise from the existing research.
And to give them credit: Is it at all useful to know if you’re acclimated to an altitude of 23′ or 600′? Probably not. It probably behooves them to pick a minimum threshold for measurement.
At the same time, if I live and train at 2550′, is my altitude acclimation absolutely zero, just like someone in Chicago (600′) or at sea level on the West Coast (0′)? Probably not. And if that hypothetical person at 2550′ goes and races at sea level, they’re probably going to exhibit more efficient, productive oxygen usage and racing performance per watt/O2/et-cetera than someone who lives at sea level.
I just ran really well at a half marathon at sea level a couple weeks ago, despite not having run the half marathon distance more than once in 2023 before that (and that was about a month before). The race felt easier overall, even in the final miles,than my prior long runs1.
Did doing all my running at 2300′ and 3000′ have a role in that? Probably. Is my altitude acclimation 0′? Probably not. It may not be exactly 3000′ (again, some of my training is around 2400′), but that it’s actually something like 2700′ or so probably does matter… even if by design Garmin/Firstbeat’s altitude acclimation metric says it doesn’t matter at all.
Who in all of peer-reviewed science exactly made the executive decision that 2620′ or 800 meters is the point where your altitude acclimation for training starts to matter at all? Research and common knowledge cited by the running community is often confounded, and often a product of relative hearsay with no research behind it. Even if there’s solid researched evidence behind it, perhaps it’s a somewhat shortsighted and hasty conclusion.
Maybe the minimum altitude acclimation threshold of 2620′ is too high. Maybe no one has ever had the sense to fundamentally question it. Or, even if anyone has the sense to question it, the scientific effort (and required sponsored research funding: To conduct a research study, someone has to sponsor it!) that’s required to document a rebuke and revision of the accepted threshold is probably considered far more trouble than it’s worth.
Most papers on sport science, not to mention running, often cite prior papers, ignoring that the original information is suspect or questionable (possibly even not backed by any research), or has limited confounding scope or application. If you ever pick up Tim Noakes’ massive book Lore of Running, he goes into immense detail on the confounding flaws of various, commonly cited studies. I’ll dodge going into more detail for now, and recommend anyone serious about running find a copy of the book and give it a read (even the first 100 pages are very insightful).
But, point being, a lot of the most commonly cited science or knowledge in running is based on some flimsy, questionably interpreted research, even given whether the research itself was properly done. Papers parroting questionable unfounded data aside, the problem often is not the research, but the conclusions people jump to from it.
One example is an old, commonly reference study on Vitamin D from sunlight during different times of the year, that led to a hasty conclusion that because the subjects’ Vitamin D levels were something like 30% lower in winter that this must mean the sun produces less Vitamin D when it’s cold.
But the study did nothing to account for what subjects wore when they were outside during the study. Obviously, they covered up more during the winter, and exposed more skin during the warmer summer. So in the winter their skin wasn’t being exposed to as much sunlight! Of course their Vitamin D levels were going to be lower in winter. That alone could have explained the difference in Vitamin D levels, but for some reason the study completely overlooked or ignored that.
Instead they claimed that the tilt of the Earth actually reduced sunlight exposure by about 30%, and now many cite this verbatim as fact, without examining the study critically and seeing what I just pointed out.
This is unfortunately common with a lot of other sport science research, and it’s not unreasonable to guess that perhaps the commonly cited altitude acclimation thresholds of ~800m or ~3000′ are based on largely arbitrary conclusions from prior research, and thus ignore the likely significant acclimation that occurs when living or training at lower but still substantial altitudes.
Now, all of that said… Garmin/Firstbeat’s 800 meter altitude-acclimation threshold may be hard-coded into their mainframe and firmware, and impossible to adjust without completely re-writing the code and releasing a new, updated watch. Given the cost and time needed to develop that, don’t hold your breath. I’m not expecting Garmin to fix something that is working correctly as it was designed.
But at least I solved this problem I’ve had after almost a year beating my head in over it. It turns out nothing in the watch is broken at all. I just found it didn’t measure my altitude acclimation because of a design limitation that incidentally overlooks my circumstances.
And of course, I don’t need a watch metric telling me anything to know that my training in Vegas has somewhat altitude-acclimated me, which turns out to be an advantage when I go down to sea level to run races.