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Fitbit users complain about forced migration to Google Health app
Google replaced the Fitbit app with a new Google Health app with an AI coach. Some users aren't happy.
The new Fitbit Edge leaks
Google’s midrange Fitbit Edge shows off is many sides and colors in leaked images.
I almost returned my Google Fitbit Air for broken sleep tracking until I changed one setting
A single tweak in Google Health revived the sleep points I'd been missing
7 first things you should do with the Google Fitbit Air
I changed these settings and set up these features immediately after unboxing my Fitbit Air.
Google Health's mistakes are a grave warning for Apple’s new AI-powered Health app
Fitbit users know how this turns out
Samsung has a new AI-powered health assistant, joining a packed market
This marks Samsung's foray into an increasingly crowded space. Whoop has an AI coach built into its platform, as does the new Fitbit Air from Google.
I couldn't have been more wrong about the Fitbit Air — here's what changed my mind
I expected the Fitbit Air to confirm everything I liked about WHOOP. Instead, after three weeks of testing, it completely changed my mind.
Garmin's New Whoop Challenger Is Also a Shot at Tech's Favorite Business Model
The Circa Smartband is a deliberate counter to the subscription-gated model that defines Whoop and Fitbit's latest tracker.
Your Fitbit data can now connect directly to Apple Health
No more third-party workarounds.
Google announces the Fitbit Edge, a middle ground between Pixel Watch 5 and Fitbit Air
The Fitbit Edge offers more than the Air, but it's not a real smartwatch.
Google's Mysterious New Fitbit Just Got a Lot More Real
The Fitbit Edge has a screen and a similar collection of sensors to the company's recent screenless wearable, according to new leaks.
New leaks reveal more details about the Fitbit Edge including its price
Google’s next fitness tracker with a screen could arrive soon.
Google Expands Automatic Activity Tracking And Brings Health Guardian To The Fitbit Air
The company announced new health features for its wearables along with a new band for the Fitbit Air.
Fitbit Air Can Turn Into a Watch and the Trick is Super Easy
When we talk about devices like the new Fitbit Air having their momentt, we can't do so without mentioning the fact that it doesn't have a screen. This is a fitness and health tracker that is...
Google Launches Women’s Health Partnership and New Fitbit
Google has launched a women’s health partnership as it deepens its footprint in the wearable fitness-tracking space. The tech giant on Monday (Oct. 12)
Google launches Pokémon Sleep special-edition Fitbit Air
Can this replace your Pokéwalker?
Here's how Apple Watch Series 11 stacks up against Oura, Fitbit, and Whoop, per WSJ
Apple Watch performs favorably in The Wall Street Journal’s health and fitness tracker showdown today. Here’s how Apple Watch Series...
Here’s how Google is responding to Fitbit users who don’t like the new Health app
Google is working on it, but the Fitbit app isn’t coming back.
Google officially teases Fitbit Edge tracker, confirms October 12 launch
Google has dropped an official teaser for its Fitbit Edge tracker and confirmed its launch date, and it's coming very soon.
I tracked sleep with Galaxy Watch Ultra 2, Fitbit Air, and Oura Ring 5. This is the one I'd buy
Which one should you share your bed with?
Google Health is here, but a lot of people want their Fitbit app back instead
How do you like your new AI health coach?
Google announces new Fitbit Air Special Edition with Pokémon Sleep [Hands-on]
The first follow-up to the Fitbit Air is a new Special Edition that integrates with Pokémon Sleep. Available in the US and Japan...
Google teases Fitbit Edge launch next week
Leaks may have already spoiled the Fitbit Edge.
Fitbit creators unveil screenless wearable to help track aging parents
The $300 Luffu Link wearable has location sharing, health sensing, a wau to ask for help, plus voice logging for medications, meals, mood and other reminders.
Google Fitbit Edge: Official Teaser, Launch Date Arrives
Google confirmed today that the Fitbit Edge is indeed real and is launching much sooner than we expected. In a short teaser posted to Twitter, Google told us to get our wallets ready on Monday. For those not familiar with Fitbit Edge, this is expected to be Google’s new fitness tracker that lands somewhere between...
Fitbit Air Review: Affordable, Minimalist Health Tracking | All Things Mobile
Google Fitbit Edge hands-on: Pixel Watch Lite, take two
Google’s new Fitbit Edge tracker launches later this month and, as we get our review together, here’s a quick hands-on...
Pixel 11 ads show a mysterious screen-equipped tracker that’s not Pixel Watch 5 or Fitbit Air [Gallery]
Google might have another fitness tracker in the works, as a pair of new ads online show off a mysterious...
Google unveils new Fitbit Edge tracker as tech giant expands health monitoring ambitions
Google on Monday its debuted its second Fitbit tracker of the year, the Fitbit Edge, which sits between the screenless health tracker Fitbit Air and the more advanced Pixel Watch. | The new device also builds on Google’s health tracking ambitions by combining advanced health sensors with AI-powered insights designed to identify changes in a user’s health and translate those signals into personalized guidance.
Google Pixel Watch Fitbit Sensor Permission Bug Leaves Health Tracking Broken for Some Users
The Google Pixel Fitbit sensor permission bug locks users out of Google Health apps by demanding sensor access already granted. Even factory resets do not fix it.
Is This a New Google Fitbit Device With a Screen?
Shortly after the launch of the Pixel 11 series and the new Pixel Watch 5, marketing materials from Google included a mystery wearable device that looked like a mix of a Pixel Watch and a slimmed-down fitness tracker. Google never did say what the device was, but we may be a step closer to finding...
Google ‘Fitbit Edge’ reportedly costs around $180 as specs & features leak
A new leak reveals that Google’s upcoming Fitbit Edge tracker will probably have a price somewhere around $180 and offer...
Fitbit Air's first update is already rolling out, and it could finally fix its biggest annoyance
Google has started rolling out the Fitbit Air's first firmware update since launch. This update promises bug fixes and improvements.
Google Releases Fitbit Air CAD Drawings & Specs: Bicep Bands Welcomed!
Google releases CAD drawings and specs for the Fitbit Air pod, allowing 3rd party companies to make band and accessories
Fitbit's Whoop Challenger Quietly Added a Game-Changing Upgrade
The Fitbit Air launched with great hardware and work-in-progress software. Now, a new partnership with a cult-favorite health startup may shore up the new tracker's biggest weakness.
Google’s Fitbit Air Gives Whoop Some Serious Competition
The Fitbit Air, a new $100 screenless wearable from Alphabet Inc.’s Google, represents a major evolution in what consumers can expect from fitness trackers as tech companies race into an era of personalized health and artificial intelligence-powered wellness insights.
Google releases Fitbit Air blueprints to let anyone make bands, accessories
Google is leaning into the Fitbit Air’s swappable pebble design to let anyone make their own accessories. This move is rather Google-y...
Google's Sleek New Fitbit Edge Is Packed With Health Features And A Replaceable Battery
The Fitbit Edge will be in stores starting October 27 for $179.99.
‘Fitbit Edge’ leaks as Google’s next fitness tracker with ‘Apps’ & ‘Notifications’
Following an accidental marketing leak in August and FCC listing last month, retail listings for the “Fitbit Edge” have now emerged.
Google Health is here, but a lot of people want their Fitbit app back instead
How do you like your new AI health coach?
Review: Fitbit Air is a near-perfect fitness tracker with an imperfect AI Health Coach
Google's latest wearable is a great tracker for an excellent price, but the Fitbit Air's AI-powered Health Coach has plenty of room to grow.
Fitbit creators unveil screenless wearable to help track aging parents
The $300 Luffu Link wearable has location sharing, health sensing, a wau to ask for help, plus voice logging for medications, meals, mood and other reminders.
4 Cool New Features Your Fitbit Air Is Getting In October 2026
With the latest update, your Google Fitbit Air can check your blood pressure trends, measure insulin resistance trends, and automatically detect more workouts.
Google Health and Fitbit Air are Getting So Many Huge Upgrades
In addition to the big news that is the Google Fitbit Edge this morning, Google also announced several major upgrades that are coming to Google Health, the Fitbit Air, and the Pixel Watch 3, 4, and 5. There’s actually more to dive into than you are probably expecting, so let’s just get straight to it....
Fitbit Edge is Google’s middle ground between Fitbit Air and Pixel Watch
Google’s newest wearable costs $179.99 and has a sleek feel like the Fitbit Air but with an OLED display.
The Fitbit Air is great, but Google's AI is too nice to be your "coach"
The Air succeeds as a minimalist, reliable fitness tracker, but Google's AI Health Coach feels unnecessary.
People are sticking the Fitbit Air to their bodies, literally, and it works [Gallery]
The Fitbit Air might be one of Google’s most versatile products in a while not just because it’s so simple,...
Google Health: Evolving so you can focus on living better
What’s new from Google Health: Explore the new Fitbit Edge, expanded workout tracking, and dedicated women's health insights.
Former Fitbit Executive Unveils New Necklace That Tracks UV Exposure
The Gem necklace can track your UV exposure.
Google announces $179 Fitbit Edge tracker with display, GPS
Google is following the Fitbit Air launched in May with a second tracker that features a screen called the Fitbit Edge.
Whatever you do, don't buy a Fitbit Edge on day one
Thinking of buying the Fitbit Edge? From early firmware bugs to Black Friday deals, here is why waiting for a few weeks is the smartest move.
Google’s new Fitbit Air brings Pokémon Sleep to your wrist
Google teamed up with the Pokemon Company to introduce a special-edition Fitbit Air that works with the Pokémon Sleep app.
Broadband access predicts health tracker use, UWM research suggests
As Fitbits, Apple watches and Oura Rings grow ubiquitous, UWM research suggests digital inequity doesn't allow them to reach those who could benefit most.
This Fitbit Air rival skips a monthly subscription, and it finally has a launch date
A smart ring company is preparing to launch its Fitbit Air rival, and it will be ditching the subscription model.
Early Fitbit Air buyers are discovering a major band fit issue
One size fits all? Not really
Possible Google device at FCC could be Wear OS-powered fitness tracker
A new piece of hardware passed through FCC certification today and the evidence points to it being a Wear OS-powered device made by Google.
Google Health adds two-way Apple Health syncing on iPhone
Back in May, the Google Health app launched alongside the new line of affordable Google Fitbit Air health trackers. Google...
The Wearable Showdown: Oura Ring 5 vs. Fitbit Air vs. Whoop MG vs. Apple Watch
Our columnist tests out the latest fitness trackers for your wrist, finger and elsewhere, with a focus on sleep monitoring and heart-rate accuracy.
Health trackers offer a ton of data. Here are the metrics doctors want you to pay attention to
We’re all wearing Apple Watches, Oura Rings, and FitBits now. Are they doing us any good?
Google Is Releasing A Special Edition Pokémon Sleep Fitbit Air In September
You can get a special Fitbit Air with a sleeping Pikachu design next month.
Fitbit Air review: Health tracking for the AI generation
The Fitbit Air is a serious rival to Whoop and other screenless wearable trackers thanks to its solid hardware, comprehensive software and competitive pricing.
Google’s $180 Fitbit Edge makes a bet on smartwatch fatigue
Google draws a sharper line between Fitbit and Pixel Watch.
Google Store Prime Day: Big deals on Pixel 10, Watch 4, Fitbit, & more
The Google Store is kicking off nearly a week of deals that coincide with Amazon Prime Day 2026. There are notable deals...
Google’s Fitbit Air Gives Whoop Some Serious Competition
The Fitbit Air, a new $100 screenless wearable from Alphabet Inc.’s Google, represents a major evolution in what consumers can expect from fitness trackers as tech companies race into an era of personalized health and artificial intelligence-powered wellness insights.
Google unveils Health Guardian features for Pixel Watch, Fitbit
During its Made by Google event on Wednesday, the tech giant announced new features, including insulin resistance, blood pressure and sleep breathing quality trends.
The Fitbit Air made me ditch my Pixel Watch, and I couldn’t be happier
I have fully ditched my Pixel Watch for the Fitbit Air and while it's a step back in utility, I couldn't be happier with that decision.
The Fitbit Air takes a smarter approach to the AI health dumpster fire
To be fair, the bar for AI consumer health is in hell.
Google debuts $180 Fitbit Edge tracker in continued health push
The new device gives Google another way to promote its redesigned health app, which debuted in May and replaced the old Fitbit user experience.
Google’s Fitbit Air is getting a shiny new Metal Mesh band and better automatic tracking
The Fitbit Air is finally getting another band option that isn’t fabric or polyurethane. Instead, the Metal Mesh band might...
I fixed my Fitbit Air's step counting with one hidden Google Health tweak
One setting made my Fitbit Air more accurate
The Fitbit Edge doesn't have NFC, and Google just revealed why
The Fitbit Edge launched earlier this month, but does this new wearable have NFC? Here's what Google told us.
Google debuts $180 Fitbit Edge tracker in continued health push
The new device gives Google another way to promote its redesigned health app, which debuted in May and replaced the old Fitbit user experience.
Google Health 5.02 finally brings back Fitbit features users have been asking for
There are over a dozen changes including many Android-first features
Google Health for Android rollout was sped up as Fitbit Air buyers were struggling to pair
The Google Health app is replacing the Fitbit app, with the update having started rolling out over the past week....
People taking GLP-1 weight loss drugs like Ozempic started moving less
People taking popular weight-loss drugs such as Ozempic, Wegovy, Mounjaro, and Zepbound may be losing pounds, but they could also be moving less. Researchers analyzing Fitbit data found that daily step counts and exercise levels dropped after people started these medications, despite successful weight loss. Because the drugs can reduce muscle mass along with fat, the decline in physical activity raises concerns about preserving strength and long-term health.
Garmin Finally Made A Screenless Fitness Tracker
The Cirqa Smart Band is Garmin’s answer to Whoop and the Fitbit Air.
Google Health roadmap details bug fixes and improvements amid backlash from Fitbit users
Google Health has replaced the Fitbit app and, with that, the major redesign has rolled out widely. Many Fitbit users...
Health coach compared 4 fitness wearables: 1 was best for performance
A health coach wore an Apple Watch, Whoop, Oura Ring, and Fitbit at once to see which is best. He found a clear winner for fitness, health, and sleep.
Fitbit’s founders designed a wearable for the whole family
Luffu, a health tracking app designed for families and caregivers, just unveiled a device that rethinks the wearable.
Fitbit founders launch Luffu Link, an LTE health and safety band
Luffu Link combines all day health sensing, voice logging, location awareness, and the ability to get help from trusted contacts into a single device, all without needing a phone nearby.
The Big Holes in Wearable Heart Rate Variability And Readiness Scores
On September 9th, Apple announced it was revamping its Apple Watch Health Sensing System, rolling out a Readiness score (0 to 10), and increasing the frequency of heart rate variability (HRV) outputs 24-fold. This can be viewed as upping its competition with various other consumer wearable sensors. These “readiness scores” as a composite of multiple metrics, with heart rate variability (HRV) being front and center for most. The majority of Americans are now using wearable sensors, which equates to well over 100 million adults. HRV and Readiness scores are increasingly being marketed as a measurement of autonomic nervous system health, a digital marker for future disease, a clock for biological age, and a holistic metric to promote healthspan and even longevity. (Apple also introduced a new longevity tab and “Health Age”.) None of this has been proven. In this edition of Ground Truths I am going to review what we know about heart rate variability and readiness scores. Heart Rate Variability HRV is the variation in normal heart cycle timing. The variability of the heart rate, the barely perceptible millisecond changes in time between consecutive heart beats (see R-R intervals in the Figure below, left panel), is due to interplay between the sympathetic and parasympathetic (vagal nerve) inputs. Distinct from heart rate, individuals with the same heart rate can have very different HRVs. It is a rough reflection of the autonomic nervous system (ANS) activity, inadequate to say whether a person’s ANS function is abnormal. For more than three decades, heart rate variability (HRV) has been measured and several studies have found an association of low HRV and clinical outcomes, particularly a link with higher all-cause and cardiovascular mortality. There have also been less well established links of low HRV to risk of early cognitive impairment, dementia, mental illness, Type 2 diabetes and substance abuse. An important reminder is that HRV is a surrogate marker without any established cause-and-effect relationship. If you increase your HRV, that doesn’t mean it will improve health outcomes. In fact, there is no hard evidence for that. All that work linking to health outcomes was done with electrocardiogram (ECG) derived HRV. Now, in the era of consumer wearables, this is getting assessed differently, by optical pulse (yes, the lights you see) plethysmography (PPG) or what is called pulse rate variability (PRV). They are not the same, as shown below (right panel) and only concordant when the delay between the ECG and pulse is kept constant, which basically means at rest. I should mention there’s also what I will call MPV, a mattress mechanical movement sensor, a derived heart rate variability, that companies like Eight Sleep use, even further away from directly measuring HRV. HRV has not one uniform measurement but many different types of quantification, such as RMSSD, the magnitude of difference between successive R-R intervals of normal sinus beats (N-N) or SDNN, the standard deviation of NN intervals, both in milliseconds. SDNN is one of the so-called frequency domain HRVs (others are LF, HF, LF/HF). Different wearable sensors use different metics; Apple has relied on SDNN and nearly all of the others use RMSSD, which is generally considered the more accurate metric. There’s also the different length of time measured, such as for a matter of minutes, all day, or an overnight’s sleep. Short measurements are especially problematic since they don’t capture enough of respiratory modulation and other factors that influence HRV. Share Ground Truths How well does HRV correlate with PRV? There are very limited studies, especially independently done. One that is commonly cited was conducted by Air Force researchers in only 13 healthy adults assessing Oura ring 3 and 4, Whoop 4.0, and Garmin Fenix 6 and showed a correlation coefficient of 0.88 to 0.97 and a mean absolute percentage error from 6 to 10%. The correlation is not a perfect 1.0, but there’s at least a fairly high level of correlation. HRV is supposed to increase during the night due to takeover of the parasympathetic nervous system, and higher during deep sleep. A recent example of my 1 week, all day “HRV,” and one during sleep is shown below. As you can see, the N of 1 data are inconsistent for the same days from different sensors (Oura, AppleWatch, Fitbit Air, and Eight Sleep) by patterns, absolute numbers, and comparison with prior days and weeks. The largest study in over 8 million Fitbit users (the old version, not Google Fitbit Air, introduced in May 2026) gives you a sense of the effect of age, sex, and the 2 different main HRV (here PRV) metrics, with RMSSD on the left and SDRR (=SDNN) on the right below. That study, from data collected in 2018, is a major outlier, since all the more recent ones are tiny with respect to sample size. Many of the companies have not had independent evaluation of their HRV, such as Eight Sleep, but have published a low standard error on their website. There are some other published studies on the correlation between HRV and PRV, but they are all small and only in healthy adults. A scoping review emphasized the lack of study in underrepresented individuals, including the aged, people of color (which affects the PPG signal), and individuals who are underweight or obese. Add the typical adult age 60 plus with one or more chronic diseases. For example, one study in over 900 adults found poor correlation of HRV and PRV, non-uniformly underestimated across many chronic diseases (cardiovascular, endocrine, neurological, respiratory, and others), concluding PRV is “an invalid surrogate for HRV.” A recent systematic review of 43 studies comparing HRV and PRV found reasonable pooled absolute standardized error (HRV as gold standard) but only 10 of the studies provided quantitative synthesis in ideal conditions. Their main conclusion was similarly cautious: “PPG-derived HRV [PRV] should not be regarded as universally interchangeable with ECG-derived HRV across all devices, populations, and recording contexts.” Factors Affecting HRV and PRV That gets me to the long list of factors that affect HRV (and PRV) besides the device, the type of measurement (RMSSD, SDNN or others), the person’s signal, the sensor site, the duration of data capture, if weighting by sleep stage is used, how artifact is processed and corrected. And this list is not complete!: Oura puts out data from their community of users (who input data) on what affects their overnight HRV. The factors currently provided are: no alcohol (increase 8%), melatonin (increase 2%, float tank (increase 2%), wine (decrease 4%), and party (decrease 14%) in overnight HRV. Must be some big parties! Subscribe What is a PRV measurement good for? It has been falsely characterized as an index of “autonomic balance” and a specific indicator of stress. A 2018 review of the studies available for HRV and its relationship to stress, not using any of the current wearables, found that stress can lower HRV. But so can many other factors. The non-specificity of the signal, indexed to the table above, is striking. Evidence from a UK Biobank study of over 46,000 participants with actual HRV looked at genetically predicted HRV, a genetic risk score, that failed to show the expected HRV-mortality link, indicating that _HRV is likely not causa_l, but rather a reflection of person’s physiologic state. A review of consumer wearable HRV data from 5 longitudinal studies showed that nighttime PRV was not associated with perceived stress, and surprisingly higher HRV, in the largest cohort (N=717 participants), was correlated with higher stress. An Oura ring cohort of 525 first-year college students found a link between overnight PRV and perceived stress, but that was also seen with resting heart rate, sleep, and respiratory rate. Several very small studies have examined the relationship of HRV and athletic injuries or guiding training with mixed, and predominantly negative results. HRV biofeedback training with paced breathing had no significant effect on reducing stress or raising HRV, as demonstrated with sham controlled trials. When HRV for multiple days showed a decline in conjunction with body temperature, the Oura ring published data for prediction of Covid. The WHOOP company sponsored an observational study, published in 2026, of 30,000 users for 72 weeks, without a control group, that reported reduced alcohol intake (5.8 % points) by self-report. That doesn’t tell us much, and particularly about the merits of HRV for behavioral change. If you use the same device and conditions as longitudinal trends for multiple (at least 2-3) weeks that may be the one way to get something useful from the measurements. Data for overnight sleep with minimal motion and using RMSSD is the best proxy for real HRV. The reason to look at trends rather than any given night is that it more likely represents something, even though you won’t know with certainty what the “it” is. Keep in mind there are no data, no peer-reviewed evidence, to show that HRV fluctuation in-person has any correlation with health outcomes. Share Readiness Scores These are proprietary scores that integrate different metrics for each of the wearables: no algorithms have been disclosed. They are unvalidated against health outcomes. In a review of 14 composite health scores of readiness and recovery, HRV contributed 86% to the scores, followed by reading heart rate (79%), physical activity and sleep duration (both at 71%). That review noted the substantial variability in measurement protools and lack of standardization. Sleep staging is notoriously inconsistent and inaccurate by these sensors, which adds further to the HRV uncertainties for what the scores, which use sleep stage data, mean. Only resting heart rate has been shown consistently across devices to be extremely accurate. I’ve made a Table to summarize what we know about which metrics are included, the scores, any peer-reviewed studies that compared the readiness score with health outcomes, and the corresponding (if any, NA-not available) citation. You will note that some companies do not use the term “readiness," such as WHOOP for recovery, and Garmin, which has 2 different scores, one of which is Body Battery. Eight Sleep uses the term “Fitness Score.” They all include HRV; Apple includes a new metric they call “Recovery HRV” which among other components uses 7-days of sleep, but it is unclear what this means or how it is differentiated from other scores (there are clearly no data for outcomes). We have no knowledge of how the different components are weighted or whether any of these scores are better than resting heart rate, HRV alone, physical activity, or any other single metric. Since none of these are standardized, they are not interchangeable, so if you get a 90 for Oura that has no relationship to a 90 on a Google Fitbit Air. Notably, the company can update its algorithm for readiness score at any point without notification to device users. Without any useful evidence of actionability for these scores or established relationship with health outcomes, it is hard to make a case for their value. At the Apple recent announcement they showed their Readiness score (0-10) on the watch (Figure below) but there are no published data on this score, not even on their website. It’s available only on their new Watch Series 12 or Ultra 4 [of course, ;-)]. That exemplifies the problems with these scores, lack of data and evidence for being meaningful to promote health. Perhaps the best study (which isn’t saying much) is the WHOOP Recovery for golfer performance, because it did correlate with an objective outcome, even though there was no control group and the authors were all from the company. Among the 389 pro golfers, an absolute 10-per cent point increase in Recovery score was associated with about 0.5 fewer strokes per round. But that’s hardly a health outcome! WHOOP is also conducting a study in over 2,700 runners to see if their recovery score will be linked to less injuries and improved performance, but that is not yet published and has no control group or randomization. Putting This in Context For two decades I’ve been enthusiastic about the potential for digital health and particularly wearable biosensors. Over the years, we’ve seen some great progress for their ability to promote physical activity and accurately detect atrial fibrillation (the first FDA cleared deep learning AI for consumers). That work was the subject of rigorous research. But there are holes in the data and evidence for other metrics. One notable one is the “VO2 max” story that I wrote about earlier this year. At that time many subscribers asked me to cover heart rate variability, which I finally got to here. When I dived into the research and publication for HRV and readiness scores, I expected to find at least some that were of high quality and demonstrated their utility by linkage to health outcomes. To my surprise, I found none. The wearable sensor measurements for HRV (PRV) are, for the most part, accurate, but that validation work has only been done in small studies of healthy adults and does not take into account the long list of factors, from the device, software side, and the user side, that affect HRV measurements. Moreover, this metric chiefly relies on optical sensing and, as we have learned for heart rate PPG sensing, may be less accurate in people of color. Keep in mind that all of the health outcome association evidence comes from ECG-derived HRV; none are from wearable sensor data. I will repeat the key point: there's no peer-reviewed evidence to show that in-person HRV fluctuation—or efforts to raise your HRV— has any correlation with health outcomes. For those of you who look at your HRV on awakening, or even 2+ week trends of it being low, I hope this context helps to relieve any anxiety. Yes, low HRV (not PRV) has been shown to increase risk of some diseases as summarized above. But efforts to raise your HRV—a surrogate metric— has not been established for improving any health outcomes. HRV does not have any evidence of causality (the genetic evidence actually goes against this possibility). In this summary, I have not included data for other wearable sensors such as Polar, Samsung, Withings, Suunto, Amazfit, Coros, Ultrahuman, or additional mattress sensors. These are beyond my first-hand experience, and as far as I know from my in-depth review none have any peer-reviewed published data that differ from the 6 sensors I’ve reviewed here. From the points I’ve gone over above, we’re not ready for readiness scores. Besides being proprietary, they are predominantly based on metrics that have their own issues. It’s compounding the problem, like building a house without a solid foundation that has never undergone a rigorous inspection, and then selling it. Like I mentioned for PRV, you can look at trends over weeks rather than any single day, to get a handle, but even that may not be helpful. There’s simply no evidence that these scores meaningfully relate to health outcomes. I’d emphasize they might, but that requires doing prospective or randomized studies to prove it. None exist. There’s great promise for HRV/PRV utility_. For example**,**_ Prof Maiken Nedergaard, who discovered the brain glymphatics that are essential in eliminating metabolic waste products from the brain during sleep, has posited that HRV could be a non-invasive marker for neuromodulator oscillations, brain-body regulatory circuits, and brain clearance. That would be extremely useful, but like everything else on HRV and readiness scores it requires solid research and validation. The lay media isn’t helping much to get the story straight. Earlier this year The Economist published a piece entitled “The most useful indicator of your overall health” which ordained HRV as an “accumulated stress score.” That’s akin to the false assertion about VO2max: “V02 max is the singular most powerful marker for longevity.” As I’ve summarized here, that is not established. The fact is that so many things can lower HRV, including physical exercise (especially an intense workout), reduced sleep quality, stress, the list above, no less the device, signal, and software. Whatever fluctuations observed have not been correlated with any health outcome. Sadly, “datamaxxers” are widely using HRV and readiness scores that have never been validated to mean anything. We already know that for some people using the sensors for sleep metrics, it can induce “orthosomnia,” an obsession to get high sleep quality, with associated high levels of anxiety. In an experiment done by a company to promote sleep quality for its employees, “For those employees who did use the trackers, many reported feeling perfectly rested until their tracker told them they had had a terrible night. Others were told that they had slept like a baby when they had actually been lying awake worrying about the quality of their sleep. “ The same problem can result from preoccupation with HRV or readiness scores, with anxiety that would lead to further reduction in both. It you are using a wearable like >100 million American adults, it’s OK to look at these data, but contextualized with the major caveats reviewed here. If you are one to require evidence that HRV or readiness scores are linked to health outcomes, you may not even want to look. The companies make it hard to turn them off! Let me end with the companies that make and sell wearables. Apple’s doubling down on HRV (24-fold more reporting and heart rate very 5 seconds) and introduction of a Readiness score tells us that consumers have bought into these metrics and they are joining the club. However, all of this is occurring with a backdrop of tens millions of users, claims about the data that are not backed up by adequate evidence, marketing way out in front of whatever limited data exists, and not being transparent about their readiness score algorithms. The companies can well afford to do the research that is needed to connect these metrics with health outcomes show, once and for all, that increasing HRV or using readiness scores promotes our health. If they believed and invested in the products they are selling, we’d not be in this position of not knowing. That’s essentially where we are with HRV and readiness scores. Perhaps someday this will change and we’ll have good reason to embrace them. NB: I wrote this post. No AI. I have no conflicts of interest with any of its content. Loading... Ground Truths has 215,000 subscribers from every US state and 214 countries. There are over 300,000 followers of Ground Truths so more than 90,000 folks who can easily convert to be free subscribers. Your subscription to these free essays and podcasts makes my work in putting them together worthwhile. If you’re not a subscriber, please join! If you found this interesting PLEASE share it! Share Ground Truths The proceeds from all voluntary paid subscriptions go to support our summer internship program. It enabled us to accept and support a record number of 62 summer interns that joined us in 2026! These are high school, college and medical students selected from thousands of applicants. We couldn’t do this expanded program without the funds coming in through Ground Truths. Thank you!
Google Home Speaker gets June release date from one retailer
Following the Pixel 10a and Fitbit Air, Google’s new Gemini-powered Home Speaker might launch on June 25, 2026.
This is the Fitbit Edge: Google's next fitness tracker finally spills its secrets
Google is reportedly getting ready to launch a new fitness tracker called the Fitbit Edge, and the device has leaked in full!
Pixel Watch is getting blood pressure tracking and new health tools this week
Pixel Watch users get major health tracking upgrades, but Fitbit Air owners will have to pay.
Your Fitbit data can now connect directly to Apple Health
No more third-party workarounds.
MrBeast will try to survive ‘the planet’s most unforgiving landscapes’ using Gemini and Fitbit Air in deal with Google
Google has struck a deal with MrBeast, the most popular YouTuber, to promote Gemini and Google Health, with one of...
Google’s Pixel Watch 5 takes notes from the Fitbit Air in latest leak
Google's Pixel Watch 5 is set to copy a key element from the Fitbit Air in the latest leak around the upcoming smartwatch.
Exclusive: This Is the Fitbit Edge, Google's Next Fitness Tracker
Exclusive Fitbit Edge images show Google's new screened fitness tracker in three colors, sitting between the Fitbit Air and Pixel Watch 5.
I reviewed the Fitbit Air, and it (almost) completely won me over
Your next fitness tracker won't have a screen, but it will have AI
I ditched Fitbit and Samsung Health tracking for this private alternative
The open-source smartwatch that does health tracking without the surveillance
Here's what it's like to use the affordable Fitbit Air that has no screen and looks like a regular bracelet
The Fitbit Air is built for people who want health tracking without the look of a fitness tracker. Here's how it stacked up in our tests.
Do More Steps Mean Better Mental Health For Teens?
By HealthDay Staff HealthDay ReporterMONDAY, Oct. 5, 2026 (HealthDay News) — A teenager's daily step count may improve more than their physical health — it may also help protect their mental health. Researchers tracked more than 5,500 adolescents (average age: 12), using Fitbits, brain scans and ...
Fitbit founders launch AI-powered wristband to monitor health of whole family
Luffu Link is a sleek, wireless wristband designed to track multiple users at once, conceived by wearable technology company Fitbit.
Google Teases Its New 'Fitbit Edge' Wearable Ahead Of An October 12 Reveal
Google has seemingly confirmed the rumored "Fitbit Edge" with social media posts teasing a new wearable coming October 12.
Google Health Update Lets You Get Rid of the Coach
Google Health was supposed to deliver us into the future of health and fitness tracking. With a refreshed app, Apple Health syncing, and a bundle of other new features, including a Google Health...
The Fitbit Air takes a smarter approach to the AI health dumpster fire
To be fair, the bar for AI consumer health is in hell.
Google reiterates missing Fibit Air sleep breathing quality feature coming ‘soon’
Google is holding off on a sleep breathing quality feature it promised for the Fitbit Air. It launched for the...
Health trackers offer a ton of data. Here are the metrics doctors want you to pay attention to
We’re all wearing Apple Watches, Oura Rings, and FitBits now. Are they doing us any good?
Capitalizing on the 'magic pill for health': Bernardston Senior Center distributes 45 Fitbits to encourage activity
The Bernardston Senior Center distributed 45 Fitbits to local seniors via a Mass COA grant to encourage fitness and healthy aging.
Fitbit Data Can Finally Sync to Apple Health
The latest update to the Google Health app for iOS allows Google Health data to sync to Apple Health. Google's app is used to collect data from wearables like Fitbit trackers and the Pixel Watch. Sync to Apple Health. Share your data like your exercise records, sleep, vitals, steps, and more from Google Health to Apple Health. Google Health (previously the Fitbit app) collects fitness, sleep, and wellness data from a connected wearable device.