[caption id="attachment_69962" align="aligncenter" width="1024"] Fenix 7[/caption] Garmin Sleep Coach - Complete BS - Insights & An Explainer *OPINION* Skip through to the end if you want to know why I think this is all complete BS. For starters, here's an explainer on how Garmin Sleep Coach officially 'works'. Garmin's Sleep Ecosystem On paper, the recently expanded Garmin Sleep ecosystem looks pretty good. We have advanced sleep tracking that, among other things, breaks down the total duration of your night's sleep into its various stages. Also added to that is a simple numeric score out of 100 and a corresponding one-word summary like 'Good'. Plus, some watches also include a sentence or so with a slightly more detailed written summary. The same data is on Garmin Connect, but here you can also see trends, overlay other data like Resting HR, and add notes. There's nothing here that's especially unusual compared to the competition. It's nice though, don't get me wrong. All the bases are covered. Well, at least the bases are now covered as Garmin's Venu 3 becomes the company's first wearable to add NAP detection and SLEEP COACH, the latter of which is the subject of this article. Two more features worth mentioning are the watch-based 'reports' that wrap around your sleep. So, a few hours before your usual bedtime, you should receive the Daily Summary (Evening Report), and in the morning, you get the appropriately named Morning Report. The evening report is new and disappointing, only providing a very simplistic yet seemingly correct summary of the kind of day you've had. On the other hand, the Morning Report is excellent; it's truly personalised and has great options for configuring just the bits of info you want to see. I suspect the Evening Report will expand over time to become more analogous to the morning report, so we can give Garmin some slack here. Anyway, back to the Sleep Coach. Sleep Coach - the Supposed Background Garmin would say that most people need between 7 and 9 hours of sleep per day. As you get older, you typically need less sleep. Then, if you work out more and more intensely, you may well need more sleep than usual. So, it seems plausible that Garmin, or any other tech company, could develop an algorithm that looks at our sleep patterns and then examines the short-term training loads we've placed on our bodies. This could be combined with a dash of HRV to determine how our bodies are coping with training stresses and the stresses of everyday life, too. How Garmin Determines Your Daily Sleep Need Garmin uses these five factors: age, daily and longer-term activity levels, recent sleep history, naps taken, and heart rate variability (HRV). Some algorithmic "magic sauce" is applied, and an adjustment factor is applied to your generic personal sleep need. For example, your normal need could be 8 hours, but that marathon you raced today bumped it up by 30 minutes. The initial calculation is made in the morning and adjusted throughout the day based on your activity and naps. The recommended amount of sleep should always be between 7 and 9 hours a day. Garmin goes as far as to say that if you need more sleep, it should come from naps. The sleep Baseline Q: What is my sleep baseline according to Garmin? A: It's 8 hours for a young adult (under 35) and falls to 7.5 hours for adults over 65 ACTIVITY HISTORY Garmin considers both sporting activity and low-level activity, like simply walking. To have these activities accounted for, obviously, you have to wear your Garmin watch. From what Garmin has publicly written about its own algorithm, it appears that only hard workouts can cause a significant increase in sleep need. Here, 'hard' would be determined both by the intensity and duration of your sporting activity, but even then, that is placed in the context of your recent training. So, it's more about whether your workout has been relatively hard. A light or inactive day may only result in a slight lowering of your sleep needs. SLEEP HISTORY When Garmin compares your 3-day sleep history to its recommendations, it adds more of its "magic sauce." Thus, if you've recently had too little or too much sleep, that can be factored into tonight's recommendations, with more weight placed on the most recent night's sleep. NAPS Garmin claims that naps are primarily light sleep and typically exclude REM and deep sleep stages. Naps will only ever lower your nightly sleep need; longer naps do so more than shorter ones. Nap Architecture, Nap architecture from infancy to older adulthood. The dimmed region represents extrapolated data. [1,10,31,124–126]Q: Is Garmin the best Sleep Tracker? A: Probably not, but it's generally good at correctly logging sleep metrics (excluding sleep stages). I'd trust tech like Oura and Eight Sleep more. Take Out So I hope you quickly skimmed through all of that and nodded along as you went. It sounds plausible, right? Here are some confounding factors Garbage in - garbage out: Garmin's raw HR should be about right for many people, but less so for HRV. However, HR also needs the context of your HR effort zones, which, from my experience, Garmin calculates incorrectly. Worse still, if you have caffeine before intense sport, at least 50% of us will have elevated HR, making our workout intensity seem higher than it is. Sleep Stages - Deep and REM sleep are fundamental to physical and mental recovery. However, no watch can accurately record these. If anyone tells you otherwise, they are wrong! If you had 2 hours of deep sleep in a 6-hour sleep, is that more impactful than 10 minutes of deep sleep in a 9-hour sleep? So you can see that truly knowing the real time spent in sleep stages is important. We just don't have that information correctly in 2023. Naps - Naps, as far as I know, can and do follow regular sleep stage cycles and so can include DEEP sleep, which often occurs near the start of sleep events in any case. Practicalities - Athletes may well need more sleep, but they simply can't sleep the extra time. 7-9 hours - While that might be a general recommendation from several health bodies, it is simply the case that there is not a magic number for you that can be determined by Garmin's magic sauce. It could be 7 hours for a 35-year-old, or 9; it's likely not the middle figure Garmin uses (8). Female? - Bad luck, most of the science hasn't considered your potentially different needs. Perception is better than measurement. - Actually, how you feel about how good your sleep was can be a pretty good assessment, and similarly, your perception of your sleep needs can also be good. Garmin could incorporate perceived/subjective factors. But hey, all those screens on your watch look pretty, right? It's not magic sauce. It's smoke and mirrors. Inconvenient Science I challenge Garmin and the wider wellness industry to say why the opinions expressed here are wrong. I'm not a scientist, but I can read, and my 30 minutes of simple Googling of scientific sleep literature and talking to 'people who know' very strongly suggests to me that sleep coaching technology in watches is only very loosely science-based. And if it's not science-based, then this non-scientist (me) can only conclude that it's almost certainly wrong and based on faulty foundations. Try these quotes from sleep research papers: There is no magic number [for sleep duration]. Chaput et al (2018, peer reviewed) and another ...Lack of females [study subjects] ...A one-size-fits-all approach to athlete sleep recommendations (e.g., 7–9 hours/night) is unlikely ideal for health and performance. We recommend an individualised approach that should consider the athlete’s perceived sleep needs. Research is needed into the benefits of napping and sleep extension. Walsh et al. (2021, Sleep and the athlete: narrative review and 2021 expert consensus recommendation) and this ..may be premature to ‘prescribe’ naps as a health enhancer...Mantua & Spencer (2017, Exploring the nap paradox) End
