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1976 Power Ballad, Recorded in New York City, Became Iconic Band's Biggest Hit
This classic hit has become an iconic ballad.
1976 Power Ballad, Recorded in New York City, Became Iconic Band's Biggest Hit
This classic hit has become an iconic ballad.
1976 Power Ballad, Recorded in New York City, Became Iconic Band's Biggest Hit
This classic hit has become an iconic ballad.
1968 Pink Floyd Track That Damaged Roger Waters' Vocal Cords Is Still a Rock Masterpiece
The song was released in 1968.
1968 Pink Floyd Track That Damaged Roger Waters' Vocal Cords Is Still a Rock Masterpiece
The song was released in 1968.
1968 Pink Floyd Track That Damaged Roger Waters' Vocal Cords Is Still a Rock Masterpiece
The song was released in 1968.
Starting Patriots defender ruled out of Steelers Week 2 matchup
The Patriots will be without a ninth-year veteran when the Steelers roll into Foxborough.
🚨 Alarm at River and Argentina over injury
River Plate’s match against Huracán is raising alarm both in Núñez and in the Argentina national team, as two injury absences have already been recorded.Thiago Almada came off before the first 10...
Week 2 injury report for the Rams
The Los Angeles Rams have posted their injury report for their Week 2 matchup with the New York Giants
Notre Dame releases injury report for Michigan State matchup
Notre Dame has released its injury report for tonight's game versus Michigan State.
Is social media giving you health anxiety? Here's how to combat it
LONDON - Do you ever find yourself caught in a health advice doomscrolling session on TikTok late at...
Is social media giving you health anxiety? Here's how to combat it
LONDON - Do you ever find yourself caught in a health advice doomscrolling session on TikTok late at...
WATCH LIVE: Pete Buttigieg keynotes Texas Democrats Johnson-Jordan Dinner
Former Transportation Secretary Pete Buttigieg delivers the keynote address at the Texas Democratic Party’s 12th Annual Johnson-Jordan Dinner as Democrats rally ahead of midterms.
📋 Vasco and Coritiba named for Brasileirão 2026 clash
It’s Brasileirão night at São Januário.Vasco and Coritiba face off from 8:30 p.m. (Brasília time).A clash valid for Matchday 28 of the competition.Bráulio da Silva Machado (SC) is the referee.A...
Another SEC Game, Another Loss for Arkansas
Arkansas’ loss to No. 2 Georgia extended the Razorbacks’ SEC losing streak to 12 games. The number does not yet match the worst conference skid in program history, but it is close enough that Arkansas can no longer treat it as a temporary concern. Another SEC Game, Another Loss for Arkansas Arkansas did not need …
Apple Watch Series 12 and Ultra 4 missing one health-focused feature
Well, this is odd. The handwashing timer feature is currently absent from the new Apple Watch Series 12 and Ultra...
Michigan State vs Notre Dame live updates: Score, highlights, analysis
Follow along live as Michigan State gears up for a rivalry matchup with Notre Dame
Latest batch of Nintendo Switch backwards compatibility fixes for Switch 2
Nintendo has been striving to get all third party Nintendo Switch games up and running and compatible with the Nintendo Switch 2. The company has been working with third party developers to ensure any…
He’s a truly, truly special person
City No.1 Gianluigi Donnarumma has lauded new boss Enzo Maresca as a brilliant coach and wonderful person. Men's Team Haaland the cover star for Sunderland matchday programme Donnarumma linked up with...
Arkansas volleyball drops final nonconference match before SEC play
The Arkansas volleyball team saw its five-match win streak end Saturday, losing to Illinois in straight sets in the Arkansas State Invitational in Jonesboro.
Exclusive: Liverpool continue to scout striker, he's scored again
Liverpool are continuing to scout and watch one of the best young strikers in Europe. He's only gone and scored again.Anfield Watch understands that Liverpool are carefully watching Paris Brunner. The...
Ed Sheeran's Tour Ticket Prices Drop, More Seats Available Amid Controversy
Shortly after Macklemore was dropped from Ed Sheeran's Loop Tour concert for his unapologetic support of Palestine, ticket prices for the singer's upcoming Philadelphia show have dropped by at least 50 percent.
Two Key Steelers Declared Out for Sunday's Matchup vs. Patriots
Pittsburgh will head to Foxborough without a few important players.
Andoni Iraola drops massive hint about Liverpool's next signing
Ronald Araujo has been a revelation since his arrival in Merseyside, and the Uruguayan has established himself already. Although initially signed as a central defender Araujo has already made a compel...
Nintendo has issued new batch of Switch 1 backwards compatibility fixes for Switch 2
Nintendo has now released new Switch 1 backwards compatibility fixes for Switch 2, and here's the full list.
J Balvin Publicly Celebrates Ex Valentina Ferrer Days After Split
J Balvín is publicly giving his ex Valentina Ferrer her flowers following their shocking breakup after a decade together.
Olid's Man Utd take big step forward after 'intense week'
A week ago, the picture at Manchester United looked bleak. Then on Saturday, victory was snatched away from them at Arsenal. But have we seen signs of improvement from Eva Olid's side?
1983 TV Movie Drew Over 100 Million Viewers, More Than Most Super Bowls
Decades later, this TV movie is still the most-watched TV movie in history.
1983 TV Movie Drew Over 100 Million Viewers, More Than Most Super Bowls
Decades later, this TV movie is still the most-watched TV movie in history.
Rabies Cases Prompt Nationwide Health Advisory: What VA Residents Should Know
Reports of people exposed to rabid or possibly rabid animals are rising across the country. Here's where Virginia cases stand.
Peacocks vs Eagles: How to watch Leeds United this weekend!
Elland Road hosts another Premier League fixture on Sunday afternoon as Leeds United welcome Crystal Palace, with the Peacocks looking to maintain their place among the early pace-setters.Daniel Farke...
Steelers Make RB, CB Reinforcements Before Patriots Game
Ahead of Sunday’s road matchup with the New England Patriots, the Pittsburgh Steelers called up veteran running back Travis Homer […]
Match Preview: Fulham vs. Manchester United
The Reds are on the road and looking for a boost after losing successive matches at Old Trafford. The controversial loss to Manchester City, to an Erling Haaland goal that should have been disallowed, was followed by a Carabao Cup exit at the hands of Brighton & Hove Albion on Wednesday. After a disappointing start […]
FSU vs. Alabama: Open thread and live game discussion
Come join our live game discussion for the Week 3 FSU vs Alabama matchup
Analysis: Glasner left with food for thought
There will be plenty to ponder for Nottingham Forest boss Oliver Glasner after this result. Forest's 24 shots today were their second most in a Premier League match since they returned to the top flight in 2022. Similarly, only Pascal Gross (15) has created more chances in the league this season than Nottingham Forest's Morgan Gibbs-White (14).
Confirmed: Injury costs Liverpool winger; Andoni Iraola forced to pivot
Liverpool don't have the winger they wanted this season thanks to injury. Andoni Iraola has been forced to pivot into something new.Liverpool quite famously lack a balanced squad right now. There are ...
Farm Safety Week to Highlight Physical and Mental Health
If you think about farm safety, you may have images of tractors, grain bins, and other equipment in mind. But
Frankie Muniz and Ex Paige Reunite for Son Amid 'Rock Bottom' Struggles
Frankie Muniz and his estranged wife, Paige Price, are putting on a united front for the sake of their 5-year-old son, Mauz.
📋 Mirassol and Botafogo named at the Maião, eyeing safety!
There is only one focus for Mirassol vs. Botafogo this Saturday (19): moving away from the relegation zone.The ball gets rolling at 5 p.m. (Brasília time) for the Matchday 28 clash in the Brasileirã...
Patriots DC calls Darnell Washington a ‘big challenge’
The New England Patriots have plenty to prepare for as they get set to face the Pittsburgh Steelers, and tight end Darnell Washington presents a particularly difficult matchup. Patriots defensive coordinator Zak Kuhr singled out Washington as a “big challenge,” pointing to the fourth-year tight end’s rare combination of size, strength and athleticism. Washington has […]
Ed Sheeran's PA Concert Undergoes Major Change Amid Macklemore Controversy
Ed Sheeran's Saturday, September 19, Loop Tour concert in Philadelphia will feature a major change as the singer continues to face backlash.
Do pimple patches actually work? Here's what the science says
You're standing in the skincare aisle and pimple patches are everywhere — clear ones, flesh-coloured ones, stars, hearts. They promise to flatten a pimple overnight. But do they work?
Chris Simms Eviscerates ESPN, 'College GameDay' For Political Propaganda
He didn't hold back.
📋 Atlético-MG reveal line-up for clash with Chapecoense
Atlético-MG are lined up to face Chapecoense in the opening match of the 28th round of the Brasileirão. Kickoff is at 4 p.m. this Saturday (19) at Arena MRV.Premiere will broadcast the match. And yo...
Northwestern vs. Colorado: How to Watch, Odds and Injury Report
Here's everything you need to know before the Northwestern Wildcats take on the Colorado Buffaloes in their final game at Northwestern Medicine Field at Martin Stadium
Steelers, Aaron Rodgers will be without top player vs Patriots
The Steelers matchup vs. the Patriots just got a lot harder.
Democrats call for investigation into faulty AI-generated intel report
A group of top Democratic senators is calling on government watchdogs to investigate a series of mistakes in US military targeting plans caused by artificial intelligence, after a CNN report detailed how one such error, according to a source familiar with the incident, “almost started a war.”
Analysis: O'Neil can be encouraged at team's display
Ipswich scored last-minute goals in their wins over Sunderland and Crystal Palace and their fans would have had hopes of more late drama when seven minutes were added on at Hill Dickinson Stadium. Town had sent on Zian Flemming, who scored their winner against Palace, but the 10 men could not score, with Flemming wasting a good chance in injury time when he fired over the top. Centre-half Issa Diop almost snatched a point right at the end, only for his effort to be charged down by a combination of Branthwaite and Garner.
Mowbray frustrated by 'patchy' Blackburn Rovers
Blackburn Rovers head coach Tony Mowbray says he is frustrated by the "patchy" form of his side.
Everyone's finally caught up to Liverpool's biggest problem: Except Liverpool
Liverpool have a massive problem on their hands and people are finally noticing. Except Liverpool, however.Liverpool spent an awful lot of money in the summer once again. Only this time, they didn't s...
Analysis: Fearless Seagulls rewarded for attacking approach
Brighton came into this match as the league's top scorers and did not disappoint with their attacking mindset. Diego Gomez on the wing did an excellent job of keeping Riccardo Calafiori quiet, while Charalampos Kostoulas caused problems for the Gunners backline throughout. The 19-year-old Greece international deserved his excellent goal, which was his third in successive games, as he looks to show he can step up to be Brighton's main striker following Danny Welbeck's summer departure to Chelsea.
Roberto De Zerbi Takes Responsibility After Aston Villa Defeat
Roberto De Zerbi took responsibility for Tottenham Hotspur’s 3-2 loss to Aston Villa, but he also raised concerns about his team’s defending, fitness, and leadership in a frank post-match press conference.
Newcastle 2-1 Hull: What Jaissle said
Newcastle have won three of their last four Premier League games against Hull (drawing the other), winning their first-ever home match in the competition against the Tigers. Lewis Hall's goal after just six minutes and 34 seconds was the earliest Newcastle have been 2-0 up in a Premier League home game since April 2023 against Spurs (Joelinton netting the second goal in the sixth minute).
Newcastle 2-1 Hull: What Jakirovic said
Mohamed Belloumi has been involved in four goals (two goals, two assists) in the Premier League this season, the joint-most by a Hull player in their first five matches in the competition, along with Mohamed Diame (four goals) and Dame N'Doye (three goals, one assist).
Training: Final prep for Sunderland clash
Check out images from training on the eve of our Etihad encounter with Sunderland. Match Preview City v Sunderland: Kick-off time and TV information The Black Cats head to Manchester for a 14:00 (UK) ...
Amazon cuts Apple Watch Series 12, Ultra 4 prices upon release
Apple Watch Series 12 and Apple Watch Ultra 4 models are on sale this weekend, with Amazon rotating discounts across case options and band colors.
Michigan Expected to Host Top-100 Quarterback for UTEP Game
Michigan is expected to host Top-100 2028 quarterback Carter Zingelmann during Saturday's matchup against UTEP.
Chicago Bears vs. Minnesota Vikings: Week 2 Players to Watch
Take a look at @BryanOrenchuk’s players to watch as the Vikings travel to Chicago in week 2.
🚨 Arsenal thrashed at Brighton!
One of the worst defeats of the Mikel Arteta era took place this Saturday.Arsenal were torn apart by Brighton (Premier League Matchday 5). Final score: 3-0 to the Seagulls against an unrecognizable Gu...
TST Best Bets: September 19, 2026
Lane Kiffin’s return to Oxford was always going to be loud. After leaving Ole Miss for LSU last season, he’ll walk back into Vaught-Hemingway Stadium on Saturday as the coach of one of the Rebels’ biggest rivals. With both teams ranked in the top 10, there’s plenty at stake beyond the reception Kiffin gets.Earlier in the day, No. 16 SMU visits No. 23 Louisville in a ranked ACC matchup. The Mustangs have opened 2-0, while the Cardinals have a chance to make an early statement at home after a 1-1
Early Games Thread – Anything Interesting Going ON? -Game Thread
I like college football, but when you look at today’s slate of games, it’s really hard to find something that might be interesting to watch. Therefore I have included all a lot of lower division games. The big game of the day is LSU-Old Miss. Possibly for the number of riots and fisticuffs that could […]
Key Injuries for Patriots, Steelers Could Determine Sunday’s Outcome
The New England Patriots and Pittsburgh Steelers are in jeopardy of missing key contributors that could affect the outcome of Sunday’s matchup.
New releases from Blancpain, Czapek, Grand Seiko and more
This past week has been one for the ages. Rolex announces an annual calendar carrying an official nickname for the first time, Blancpain releases one of the smallest mechanical movements to date, and Grand Seiko brings back Arabic numerals after 25 years. There’s plenty more too, spanning other all sort of styles and budgets with … Continued
Ravens - Saints: How to Watch, Predictions, and More
Everything to know about the Baltimore Ravens' home opener against the New Orleans Saints.
Chicago Bulls Guard Expected to "Dominate" Trade Conversations
A newly signed veteran could quickly become one of the league’s most closely watched trade candidates, though the Chicago Bulls' emerging young core may give the team reason to keep him.
Haaland the cover star for Sunderland matchday programme
Erling Haaland is our cover star for the matchday programme for City’s game against Sunderland on Sunday. Interviews Maresca: Opening day win was important for current form The City striker is also ...
How to watch Memphis’ home game against UT Martin
Memphis returns to action at Simmons Bank Liberty Stadium for its final non-conference game against UT-Martin. The Tigers will look to bounce back following a 38-20 loss against Boise State.
Iconic 40-year-old beer brand closing down its beloved brewery
One of the first brewpubs to open in the U.S.
Apple Watch Ultra 4 Sees First Discount After Launch, Now $779.99 on Amazon
The new Apple Watch Ultra 4 just launched yesterday, and Amazon is offering the first cash discounts on select models for the first time since their launch. You can get the Apple Watch Ultra 4 in Natural with Translucent Gray Ocean Band for $779.99, down from $799.00. Note: MacRumors is an affiliate partner with some of these vendors. When you click a link and make a purchase, we may receive a small payment, which helps us keep the site running.
Week 3 Game Predictions: Northwestern Wildcats vs. Colorado Buffaloes
The predictions are in for Northwestern vs. Colorado as the Wildcats return from their bye week for a highly anticipated Week 3 matchup.
Steelers CB Joey Porter Jr. ruled out vs. Patriots
Per the Pittsburgh Steelers’ Friday injury report, cornerback Joey Porter Jr. (NIR/conditioning/back) is out for Sunday’s matchup with the New England Patriots.
WSL: Arsenal host winless Manchester United
Follow live text commentary, score updates and match stats as Arsenal take on Manchester United in the Women's Super League.
🤝 Deco: Raphinha, Bernal and Espart extensions agreed
As a warm-up to tonight’s match against Sevilla, FC Barcelona held its ordinary assembly of delegate members, featuring noteworthy remarks from president Laporta and also from Deco. The latter took ...
Saturday football open thread
Tottenham may have already played, but there’s plenty of football yet to play today. This is your open thread for that match. Post away. Saturday Match Schedule Brighton vs. Arsenal10 am ET / 3 pm BSTTV: USA Network (USA), not televised (UK)Stream: nbcsports.com Everton vs. Ipswich10 am ET / 3 pm BSTTV: NBCSN (USA), not […]
Apple Watch Series 12 might finally convince me to switch away from WHOOP
Earlier this year, I picked up a WHOOP for the very first time. As a longtime Apple Watch user I...
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!
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