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Results for " summer " 3,236 found 🔀 AI-powered Shuffle
The calendar says it’s 2026, so why does it suddenly feel like 2028?
Summer’s swampy heat released its grip on Washington Tuesday as if someone had flipped a switch.
A record-breaking Bianconeri summer: thousands of youngsters involved worldwide
Bianconeri emotions, training sessions, smiles, football and outstanding locations around the world. The Juventus summer of 2026 provided unforgettable experiences for more than 6,000 young football e...
Chief Counsel told staff early not to use Signal
The influencer issue this summer left the group chat.
Conn Smythe Winner Jonathan Marchessault Poised for Bounce Back Season
After one of his worst seasons in the NHL, Nashville Predators forward Jonathan Marchessault is ready to bounce back in 2026-27. The 2023 Conn Smythe winner was a shell of himself last year as the Predators failed to make the postseason for the second year in a row. Nashville made several moves this summer. One […] The post Conn Smythe Winner Jonathan Marchessault Poised for Bounce Back Season appeared first on HEAVY.
Green policies just good politics, says UK minister
Transitioning to a low-carbon economy isn't just vital for the planet's future -- it's also good politics, according to Britain's climate minister, who argues the country's record-hot summer has galvanized public opinion like never before. Katie White, a member of the ruling Labour government, said the UK's right-wing parties had…
Day-into-night music, entertainment. Popular Turlock eatery to mark summer’s end
It’s a family friendly celebration with no cover charge.
State health officials confirm new measles case in Chippewa County
State health officials have confirmed a new case of measles in Chippewa County, marking the latest infection in Wisconsin since late summer.
Mike Babcock Already Holding Oilers’ Feet to the Fire
The Edmonton Oilers made a controversial decision during the summer upon the terminations of head coach Kris Knoblauch and assistant coach Mark Stuart.In Knoblauch’s place, GM Stan Bowman hired Mike Babcock, who had most recently been with the Columbus Blue Jackets in 2023 but resigned before having ever coached a game with the club due […] The post Mike Babcock Already Holding Oilers’ Feet to the Fire appeared first on HEAVY.
Armand Hammer's private art collection arrives at Sotheby's L.A.
Hammer Museum founder Armand Hammer's private art collection will go up for auction after a preview exhibition at Sotheby's L.A. Works include Mary Cassatt's "Summertime" and Edgar Degas' "Trois danseuses."
Graham says getting first Scotland call-up was 'surreal'
Luke Graham says getting his first call-up to the Scotland squad was "pretty surreal". The 22-year-old defender has impressed since making the summer switch to Stoke City, playing eight games so far in the Championship. Sebastien Pocognoli included the former Dundee defender in his first Scotland squad - a pleasant surprise for the Graham family.
Club director denies ripping Arsenal off for summer signing
Hamburger SV sporting director Claus Costa has denied ripping Arsenal off for Fabio Vieira, but he conceded that HSV are very happy with the deal they agreed.Photo by Stuart Franklin/Getty ImagesHambu...
Inter Not Getting Much Contribution from EPL Signings
Inter based their summer strategy on bringing in players from the Premier League to try to get closer to those powerhouses in Europe, but the early returns have been paltry at best. Only Curtis Jones ...
Summer spending put Alonso in 'impossible position'
Chelsea's Xabi Alonso as well as Roberto de Zerbi of Tottenham are in an "impossible position" this season, believes The Observer's Rory Smith. The managers took charge of their clubs in the spring and oversaw a lot of activity in the transfer window, with Chelsea and Spurs ending the summer as the second and third-highest spenders respectively. Smith says the changes to their squads is why Alonso and De Zerbi need time to build coherence in their sides.
Is Roberto De Zerbi Misusing Mateus Fernandes For Tottenham?
Mateus Fernandes has struggled to make an impact for Tottenham Hotspur since joining from West Ham in the summer.
York Beach businesses saw crowds — but a quieter summer at the register
York Beach businesses say summer spending dipped as visitors tightened budgets.
York Beach businesses saw crowds — but a quieter summer at the register
York Beach businesses say summer spending dipped as visitors tightened budgets.
Juventus plans to sign €50m goalkeeper in the summer
Marco Carnesecchi has been on Juventus’ radar since he was on loan at Cremonese some years ago, and they are ready to make a significant investment to sign him at the end of this season.Luciano Spal...
CSU experts say rising heat will negatively impact academics this fall
Fort Collins just logged its warmest summer on record. Nighttime lows aren’t dropping the way they used to. And through most of September, nearly every day has landed above the historical average for the month. For Colorado State University students, that’s more than a matter of sweating through class; researchers say it could be shaping...
Scientists found 9 new sea sponge species in Alaska
Two studies published this summer describe the new species, which were found in the Gulf of Alaska and Aleutian Islands.
Santa Fe businesses report mixed results from summer tourism season
Randy Randall of Tourism Santa Fe said he wasn't disappointed considering the position of many other American tourism destinations.
Green policies just good politics, says UK minister
Transitioning to a low-carbon economy isn't just vital for the planet's future -- it's also good politics, according to Britain's climate minister, who argues the country's record-hot summer has galva...
Juventus considering shock move for Inter’s Hakan Çalhanoğlu next summer
As reported by TuttoJuve.com, Juventus are considering making a move for Inter midfielder Hakan Çalhanoğlu next summer.The veteran Turk has started this season in goal-scoring form, having already n...
Raphinha's Great Start To The 2026/27 Season
Every fan who’s been following FC Barcelona during the past few seasons knows how important Raphinha has been to the team. Temporarily losing him due to injuries often meant a decline in the team’s performance, and he became widely respected among the Culers. After the summer break, he has seemingly ascended to another level, exceeding […] The post Raphinha’s Great Start To The 2026/27 Season appeared first on Stadium Rant.
Jaquet's performance against Bournemouth 'a step forward'
Defender Jeremy Jacquet's performance in Sunday's 1-0 win at Bournemouth was "a step forward" in his development, according to Liverpool boss Andoni Iraola. The 21-year-old centre-back was named player of the match against Iraola's former side after another assured display, completing his third full 90 minutes in a row in the Premier League. A five-year deal was agreed in January to sign Jacquet from Rennes this summer, but he suffered a shoulder injury soon afterwards that ruled him out of the rest of the campaign.
Trump decries Democrats as ‘communists,’ even as he looks to impress China’s communist leader
WASHINGTON (AP) — Communism, President Donald Trump says, is the greatest threat the U.S. has ever faced. This summer, citing similarly grave concerns, he took the rare step of delivering a primetime address to the nation, accusing China of “sinister election meddling” in 2020 and reviving his yearslong push to dispute his loss in that […]
Houston high school football: Week 4 takeaways and top performers
Week 4 of the Houston high school football season produced several intriguing results, including high-scoring wins for Klein Cain, Friendswood, Dickinson and Summer Creek.
Fuseini brings Rams hope of a revival
Derby County fan writer Amelia Warren analyses what makes Mohammed Fuseini an important summer signing for Derby County this season.
Schalke defender frustrated by lack of contract talks
With his contract expiring next summer, Schalke 04 centre-back Hasan Kurucay has expressed his disappointment that the club have yet to approach him about an extension.“I haven’t heard anything fr...
CMU makes progress on Hall of Sciences, campus improvements
Construction of the Richard King Mellon (RKM) Hall of Sciences progressed over the summer. Carnegie Mellon broke ground on the new building in June 2024 and expects expected to finish on schedule.
Roma Taking an Extended Look at Free Agent Defender
Roma could take advantage of the extra-long break to bring in a free agent and have had some contacts with Matteo Darmian as of late. He has been approached by a few smaller sides during the summer, b...
Here are seven candidates for song of the summer
These are seven songs that could be song of the summer for 2026. Candidates include artists like Karol G, Olivia Rodrigo and Ella Langley.
Juventus to Continue to Dabble in Goalkeepers’ Market
Despite signing two goalies last summer, Juventus could soon put another one under contract, as Kamil Grabara suffered an ACL tear in training and will miss most of the season. The Bianconeri are eval...
Bruno Genesio provides Igor Paixao injury update
Olympique de Marseille did everything to retain Igor Paixao (26) over the summer. Amid the club’s financial problems, the ownership looked to offload the Brazilian in the closing days of the transfe...
Suki Waterhouse Announces December Tour Dates, Timed Close to Robert Pattinson's Next Blockbuster Release
The English singer's major-label debut album was released over the summer.
Suki Waterhouse Announces December Tour Dates, Timed Close to Robert Pattinson's Next Blockbuster Release
The English singer's major-label debut album was released over the summer.
TV Shocker: 96% RT James Bond-Like Show Canceled by Prime Video
Prime Video has pulled the plug on one of its most-watched originals of the summer. The streamer declined to renew the spy comedy starring Hannah Waddingham and Octavia Spencer for a second season. Pa...
Hailey Bieber Unveils Her Darkest Hair Transformation in More Than a Decade
The dramatic change comes after Bieber told followers this summer that she was on a "hair health journey.".
Phoenix Suns 2026-27 Player Profile: Khaman Maluach
After a tantalizing Summer League, the Duke product enters a pivotal sophomore campaign. Discover how his floor-spacing potential and defensive growth could propel him into the starting lineup.
Happy birthday, Kerim!
Kerim Alajbegovic is celebrating his first birthday in black and white. Today, Monday 21 September 2026, he turns 19 years old.The young Bosnian talent, who arrived in Turin this summer, has made a to...
Why politicians should pay more attention to the polls (reprise)
Welcome to the 231st edition of The Week in Polls (TWIP), a polling newsletter that always welcomes new readers. So please don’t keep TWIP a secret; share it with your friends and colleagues: Share The Week in Polls With all the stories swirling around Reform, JL Partners and political polling, I am finally tearing myself away from talking about the regulation of polling this week - and instead re-running a previous piece reminding us why the solution to problems with polls isn’t simply to ban or ignore them. Rather, we need them to play a vital role in making our politics - and politicians - better. This is followed by summaries of the latest national voting intention polls, seat projections from MRPs and the most recent party leader ratings. Subscribers who pay for the full edition can also read ten insights from the latest polls and analyses, including: A trio of organisations and a pair of professors have been casting their eyes over the Liberal Democrats ahead of the party’s autumn conference; What impact did the summer heatwave have on views on climate change? and Which wins out between chocolate and cheese? If you are not yet a paid subscriber, you can read all ten by starting a free trial now: Get FREE 7-day trial For more polling news as it comes in ahead of next week’s edition, you can also follow The Week in Polls on Bluesky. Picking up on my doubt last week about whether or not 35% of British train travellers have tried to order a takeaway for delivery to a railway station or carriage, thank you to reader Iain, who has been in touch to say he has done just that… in India. Another quick pair of updates, this time on the controversies around Reform and polling. Politico has a further scoop - “Farage aide caught in donor sting attended Egypt retreat with JL Partners” - and Ian Dunt has written about the problems with polling too: “Seeing the response of many polling experts in the last few weeks suggests that they are nervous about what is happening and keen to mitigate against it. Seeing the response of journalists, which has been basically non-existent, suggests the precise opposite.” My usual reminder as well: please do hit reply if you’ve spotted a poll, focus group or new piece of poll-based research that you think should be in contention for coverage in a future edition. Thank you! And with that, on with the show. How politicians get public opinion wrong I have written before about the benefits that come from widespread availability of high-quality political polling. We need more polls and more good coverage of polls. However, what I’ve not dug into before is the research into how accurately politicians estimate public opinion on issues. Thankfully we have academic research to tell us. First, the bad news: We present results from a study of 866 politicians in four countries.1 Politicians were asked to estimate the percentage of public support for various policy proposals. Comparing more than 10,000 estimations with actual levels of public support, we conclude that politicians are quite inaccurate estimators of people’s preferences. They make large errors and even regularly misperceive what a majority of the voters wants. Politicians are hardly better at estimating public preferences than ordinary citizens. Walgrave, S., Jansen, A., Sevenans, J., Soontjens, K., Pilet, J.B., Brack, N., Varone, F., Helfer, L., Vliegenthart, R., van der Meer, T., Breunig, C., Bailer, S., Sheffer, L. & Loewen, P.J. (2023a), “Inaccurate Politicians: Elected Representatives’ Estimations of Public Opinion in Four Countries”, The Journal of Politics, 85(1): 209-222. The bad news is not quite as bad as that makes it sound because, when asked whether the majority of public opinion was for or against various policies, politicians picked the wrong option ‘only’ 29% of the time. However, this included getting it wrong even when public opinion is far from evenly split on an issue: They do not only get it wrong when the public is divided and hard to read (e.g., when there is a 51%:49% distribution). Seventy percent of the misplacements occur for policies with a relatively clear distribution of at least 60% (dis)agreeing citizens. Moreover, the public scored only slightly worse than politicians, picking the wrong option 2.7 out of 8 times on average, compared with 2.3 times for politicians. Turning to the other measure of accuracy (not which side is in the lead but what the percentage support is for each side), politicians on average were 18 percentage points out in their guesses. Again, this was only slightly better than the public, whose error came in at 21 percentage points.2 Further research, using the same mix of countries, gives a little more comfort about how (in)accurate perceptions are: We show that politicians have a better understanding of public opinion when they think the issue matters to voters. Further, when an issue is personally important to politicians they more accurately estimate their party supporters’ opinions. The results confirm that politicians hold more accurate perceptions of voters’ preferences when they think it is important to do so but not necessarily when the issues actually are important to voters. Butler, C., Walgrave, S., Soontjens, K. & Loewen, P.J. (2024), “Politicians are better at estimating public opinion when they think it is more salient”, Party Politics: 1–13. Even so, it’s not a good picture. The remedy for this? Politicians should spend more time reading the polls. So forward this newsletter to someone you know… Share For a more general argument against banning polls, see my 2024 piece. Is “Let Bartlet Be Bartlet” good advice or not? The latest episode of my Political Fictions podcast heads across the Atlantic for a dip into one of the political TV classics: Mark and Cory talk about a giant of American political drama for the first time this week, as they tackle The West Wing. They talk about Let Bartlet Be Bartlet, the nineteenth episode of series one. In it, Mark wonders if The West Wing is actually the epitome of the “Boris Johnson school of politics”, Cory outmanoeuvres Mark into confirming we will record a Christmas Special about Love, Actually and they debate whether the central message of this episode has been misunderstood. Cory’s email newsletter is Paperback Rioter and Mark has a family of email newsletters. Subscribe to our newsletter for some additional bonus content and to get alerted whenever a new episode comes out. Our theme tune is “Monkeys Spinning Monkeys” by Kevin MacLeod/incompetech.com and licensed under the Creative Commons: By Attribution 4.0 License. You can also listen to our episode on Apple Podcasts, Spotify, the web or YouTube. Elsewhere from me… [ A Lord's Eye View How to fix the problem of money in our politics Welcome to my latest update on work in the House of Lords. This time I am taking a look at how our political system is regulated, and the protections we need to keep democracy safe from becoming simply a contest to see who has the biggest bank account… Read more 5 days ago · 3 likes · 2 comments · Mark Pack ](https://lordseyeview.substack.com/p/how-to-fix-the-problem-of-money-in?utm_source=substack&utm_campaign=post_embed&utm_medium=web&embedding_publication_id=1269283) If you spot a factual error… Borrowing an idea from Stuart Ritchie and others, if you spot a factual error in an edition of this newsletter, I will give you a free 12-month subscription to the paid-for version (or an extra 12 months on your existing one). Factual errors qualify, but grammatical errors or disagreements over interpretation do not, and my decision is final. Messages about both of those are always welcome, though. Voting intention and leadership ratings Here are the latest voting intention polls from different pollsters. It is all pretty static at the moment, with a small and consistent Labour lead in nearly all the polls. The table is also online here, along with explanations about what is included. It is updated regularly throughout the week as new polls are released. Next are the seat projections from MRPs, also sorted by fieldwork dates, listing those which are based on dedicated fieldwork (rather than models based on averages of other polls). Because such MRPs are published infrequently, some of the entries below are quite old. Finally, here is a summary of leadership ratings, with a graph from PollCheck: Detailed numbers from the latest polls are online here, and both that and the graph are updated regularly throughout the week as new data comes out. For historical figures on both voting intention and leader approval stretching back to the 1930s, including Parliamentary by-election polls, see PollBase. Catch up on the previous two editions [ ](https://theweekinpolls.substack.com/p/a-crisis-point-for-political-polling) [ A crisis point for political polling Sep 13 ](https://theweekinpolls.substack.com/p/a-crisis-point-for-political-polling) [ Read full story ](https://theweekinpolls.substack.com/p/a-crisis-point-for-political-polling) [ ](https://theweekinpolls.substack.com/p/extra-questions-about-the-polls-in) [ Extra questions about the polls in Reform’s funding scandal Sep 6 ](https://theweekinpolls.substack.com/p/extra-questions-about-the-polls-in) [ Read full story ](https://theweekinpolls.substack.com/p/extra-questions-about-the-polls-in) My privacy policy and other legal information are available here. Links to purchase books or other items are usually affiliate links which pay a commission for each sale. Quotes from social media messages are occasionally lightly edited for punctuation and clarity. If you are subscribed to other email lists of mine, please note that unsubscribing from this one will not automatically remove you from the others. If you wish to be removed from all my lists, simply reply to this email to let me know. A quintet of Lib Dem polling analyses, and 9 other polling insights you shouldn’t miss The following ten findings from the most recent polls and analyses are only for subscribers who pay for the full edition, but you can sign up for a free trial to read them straight away. Ahead of the start of Liberal Democrat conference, we have a trio of organisations and a pair of professors with pieces out about Ed Davey’s party:
Octavia Spencer's Hit Summer Series Canceled After Just 1 Season - But Studio Could Bring It Elsewhere for...
"Prime Video has shot itself in the foot so many times, I can barely believe they're even standing," said one fan.
Orlando Science Center opens renovated theater
A lot is happening at the Orlando Science Center. The organization recently reopened the Dome and hosted a series of sold-out laser shows this summer. A new exhibit called “Extreme Sports: Beyond Human Limits” opens in late September, showing visitors what it’s like to rock climb and use a flight suit. To top it off,
Liverpool eyeing fourth £100 million signing for January
One of the key weaknesses in the squad that Liverpool failed to address in the summer is the right-wing position. With Mohamed Salah no longer at Anfield and Federico Chiesa out injured, the Reds are ...
Ducks Sign Tim Washe to Four-Year Extension
The 25-year-old was set to be a restricted free agent with arbitration rights next summer.
Furbank to miss opener
GEORGE Furbank suffered a nightmare start to his new life at Harlequins after he was forced off a minute into his club debut on Friday night. Furbank, who joined the London club from Northampton over the summer, is likely to miss his new club’s Premiership opener against Bath on Friday after he was caught by […] The post Furbank to miss opener appeared first on The Rugby Paper .
Chris McKenna Made Sure One Special Costar ‘Got Her Flowers’ Before ‘General Hospital’ Exit
Chris McKenna and Paige Herschell exited 'General Hospital' as Jack Brennan and Jacinda Bracken departed Port Charles in dramatic fashion this summer.
Liverpool sends warning to Arsenal over their teenage sensation
Arsenal have been linked with a move for Liverpool starlet Rio Ngumoha, but the Gunners have reportedly been warned by the Reds to stay away from the teenager.During the summer, Bayern Munich targeted...
Sunflower Troupe seeks Four Corners playwrights for 2027 short-play festival
Selected works will be performed next summer
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.
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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