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ESPN's Kirk Herbstreit Caught Blocking Fans Who Call Out His Past Political Comments
The ESPN analyst appears to have been caught.
ESPN's Kirk Herbstreit Caught Blocking Fans Who Call Out His Past Political Comments
The ESPN analyst appears to have been caught.
ESPN's Kirk Herbstreit Caught Blocking Fans Who Call Out His Past Political Comments
The ESPN analyst appears to have been caught.
ESPN's Kirk Herbstreit Caught Blocking Fans Who Call Out His Past Political Comments
The ESPN analyst appears to have been caught.
ESPN's Kirk Herbstreit Caught Blocking Fans Who Call Out His Past Political Comments
The ESPN analyst appears to have been caught.
Man City outlast Sunderland in eight-goal thriller, Liverpool win
Brian Brobbey scored a hat-trick in a losing cause as Manchester City maintained their 100% Premier League start with a frantic 5-3 win over Sunderland on Sunday. In a game characterised by poor defending, City struggled to kill off the fired-up visitors at the Etihad Stadium, with Brobbey a constant thorn in their side.
Carole King Wrote 'Will You Love Me Tomorrow' at 18 and It Became the First No. 1 Song by Any Girl Group;...
The Shirelles almost said no.
Nicolas Cage, 62, Reveals Striking White Hair and Beard Transformation With Wife Riko Shibata, 31
Look at that full white beard!
🚨 Manchester City wobble, Liverpool steady themselves!
Three goals conceded, but… the win is there! A strange afternoon for Manchester City at home, as they ran out 5-3 winners against a tough Sunderland side.Dutch international Brian Brobbey grabbed a ...
Meg Ryan's Son Jack Quaid Towers Over His Mom in a Rare Red-Carpet Moment
Meg Ryan rarely hits the red carpet!
Meg Ryan's Son Jack Quaid Towers Over His Mom in a Rare Red-Carpet Moment
Meg Ryan rarely hits the red carpet!
Optimism and tight polls: Can Florida Democrats flip Sunshine State blue in 2026?
Florida Democrats gathered in Miami with renewed hope as tight polls signal potential turnarounds in key 2026 midterm races.
Hayden Christensen and Rachel Bilson's Daughter, 11, Hits the Red Carpet Holding Hands With Dad
Holding hands with her dad!
The Nerazzurri players called up for international duty
For the first time this season, league action pauses to make way for international fixtures. There is a change to the format compared with recent years: for the first time, each national team will pla...
Will Sharpe Jokes Unlike His Artist Character in “In Waves”, His Art ‘Looks Like Somebody Is Going Through Psychosis’ (Exclusive)
Sharpe voices AJ in the new animated film ‘In Waves,’ which premiered at the Toronto International Film Festival on Sept. 14
Legendary Rock Band Drops Out of Louder Than Life Music Festival Due to Medical Emergency
The bassist could not perform.
Legendary Rock Band Drops Out of Louder Than Life Music Festival Due to Medical Emergency
The bassist could not perform.
Kyle Tucker Provides Health Update After Dodgers Win Over Giants
Kyle Tucker provides injury update.
Kyle Tucker Provides Health Update After Dodgers Win Over Giants
Kyle Tucker provides injury update.
Iran’s Human Rights Council Condemns Israeli Regime Attack on Lebanon Hospital
TEHRAN (Tasnim) - The High Council for Human Rights of the Islamic Republic of Iran has strongly condemned the Israeli regime forces’ attack on the Mays al-Jabal public hospital in southern Lebanon as a blatant violation of fundamental human rights principles and international humanitarian law.
Every '80s High Schooler Knew Every Word to This B-52's No.1 Hit; Rolling Stone Ranked It as One of the...
The tune almost never happened, Fred Schneider based it on a real club he used to visit.
Every '80s High Schooler Knew Every Word to This B-52's No.1 Hit; Rolling Stone Ranked It as One of the...
The tune almost never happened, Fred Schneider based it on a real club he used to visit.
Ed Sheeran Found New Band to ‘Stand on Stage With Me' After Controversy
Ed Sheeran performed with a new backing band during his Saturday, September 19, concert after his previous team left the Loop Tour in solidarity with Macklemore's controversial departure.
Arsenal performance not fit for champions
Bruno Guimaraes said Arsenal's "unacceptable" performance in their defeat at Brighton & Hove Albion was not fit for a Premier League champions' shirt. Arsenal's 100% start to the new season ended in abrupt fashion as Brighton put Mikel Arteta's side to the sword with a brilliant 3-0 victory.
The First American Sitcom Aired 79 Years Ago, With Episodes on CBS and NBC
The show starred a real couple.
The First American Sitcom Aired 79 Years Ago, With Episodes on CBS and NBC
The show starred a real couple.
The First American Sitcom Aired 79 Years Ago, With Episodes on CBS and NBC
The show starred a real couple.
The First American Sitcom Aired 79 Years Ago, With Episodes on CBS and NBC
The show starred a real couple.
'The First Wives Club' Turns 30, Its First Milestone Since Diane Keaton's Death
"It was the best of times," Bette Midler has previously said of filming the movie.
'The First Wives Club' Turns 30, Its First Milestone Since Diane Keaton's Death
"It was the best of times," Bette Midler has previously said of filming the movie.
'The First Wives Club' Turns 30, Its First Milestone Since Diane Keaton's Death
"It was the best of times," Bette Midler has previously said of filming the movie.
1993 Classic, Starring Kurt Russell, Features the ‘Greatest Western Movie Character of All Time'
This film became a success at the box office.
1993 Classic, Starring Kurt Russell, Features the ‘Greatest Western Movie Character of All Time'
This film became a success at the box office.
1977 Fleetwood Mac Hit, Written by Christine McVie, Wasn't About a Dog
Christine McVie tried to hide the inspiration behind one of her biggest songs.
1977 Fleetwood Mac Hit, Written by Christine McVie, Wasn't About a Dog
Christine McVie tried to hide the inspiration behind one of her biggest songs.
Oracle CEO tells employees AI has not sped up product delivery
Oracle's chief reveals what the AI productivity boom is missing.
Oracle CEO tells employees AI has not sped up product delivery
Oracle's chief reveals what the AI productivity boom is missing.
Oracle CEO tells employees AI has not sped up product delivery
Oracle's chief reveals what the AI productivity boom is missing.
Who passed health checks in Wichita KS? Burgers, coffee, Mexican food & more
See Wichita-area restaurants, stores & hotels that passed health inspections. Thirty-five locations made the Sept. 6-12 list.
Dolly Parton Carries This Shocking Home Item ‘Non-Stop' While Touring
Miley Cyrus questions Dolly Parton's mobile tub: "When are you taking the bath on the highway?".
Global trade takes to North Texas in this week's business datebook
The Taiwan External Trade Development Council brings back Taiwan Expo USA for the third year to the Kay Bailey Hutchison Convention Center Dallas.
‘Sweet Magnolias' Creator Breaks Silence on Show's Shocking Cancellation
Sweet Magnolias creator Sheryl J. Anderson just broke her silence after the show's shocking cancellation.
‘Sweet Magnolias' Creator Breaks Silence on Show's Shocking Cancellation
Sweet Magnolias creator Sheryl J. Anderson just broke her silence after the show's shocking cancellation.
‘Sweet Magnolias' Creator Breaks Silence on Show's Shocking Cancellation
Sweet Magnolias creator Sheryl J. Anderson just broke her silence after the show's shocking cancellation.
Sunday football open thread
It’s the last Premier League football for three weeks, as the new, ridiculous super-international break starts tomorrow. However, there’s plenty of woso to come, with Spurs Women playing FIVE MATCHES before the men play another game. That said, we might as well have an open thread for the remaining Premier League matches today in addition […]
1969 Elvis Presley Gem Was the Flip Side of a No. 3 Billboard Smash
While 'In the Ghetto' dominated the radio, its soulful B-side proved to be a masterpiece of its own.
1969 Elvis Presley Gem Was the Flip Side of a No. 3 Billboard Smash
While 'In the Ghetto' dominated the radio, its soulful B-side proved to be a masterpiece of its own.
PSG XI vs Marseille – Predicted lineup and team news
PSG will be aiming to record a third consecutive victory in all competitions before the first international break of the season when they travel to face Marseille on Sunday.PSG head into Le Classique ...
Like live music? How about free? Then this concert series is for you.
Exploration Place won a three-year Levitt Family Foundation grant for a concert series that started this fall.
Mariska Hargitay Walked Onto a Set 27 Years Ago and Never Left It; No Actor in American Primetime Drama...
The two Emmys she won this month had nothing to do with Olivia Benson.
Mariska Hargitay Walked Onto a Set 27 Years Ago and Never Left It; No Actor in American Primetime Drama...
The two Emmys she won this month had nothing to do with Olivia Benson.
How President Trump Broke the Kennedy Center
Internal emails and documents demonstrate the political capture of the institution, including how officials once pursued a plan to unload much of the art collection.
Woody Harrelson and His Wife Look So in Love on the Red Carpet
Now that's one happy couple.
Zinédine Zidane calls time on N’Golo Kanté’s France career
Zinédine Zidane, in evoking the subject of a potential return for Karim Benzema (38), announced that N’Golo Kanté’s (35) time as a France international is over. Kanté was involved in the most r...
Scotland must show more belief
Evie Gallagher says Scotland must believe they belong amongst the world's best if they are to compete against the top international sides. The number eight scored both of Scotland's tries against New Zealand but the Black Ferns were a class apart as they ran in 10 tries for a 66-14 victory at Hive Stadium. It was a second straight defeat for the Scots in the WXV Global Series following last weekend's defeat to Canada.
1968 Monkees B-Side, Written by Mike Nesmith, Found New Life on a Hit 2020s Series
Decades after it was buried on the back of a hit single, 'Tapioca Tundra' entertained a whole new generation of 'Better Call Saul' fans.
Brighton's Pascal Groß retires from international duty with Germany
After scoring in Brighton & Hove Albion’s 3-0 win over Arsenal on Saturday, Pascal Groß announced that he has decided to retire from international football with Germany.The 35-year-old was part of ...
☀️ Estupinan starts, Soulé frustrated, Koop benched: morning news
The fifth round of Serie A continues on the day that will then lead into the long break for international duty.Watch the entire Serie BKT live with LaB Channel on OneFootball: subscribe for just €9....
Announcers, Referees and Jersey Combination for Cardinals Week 2 Game vs. Seahawks
Get the full Week 2 game details for Cardinals vs.
World Organization for Science Literacy launched in Beijing
The World Organization for Science Literacy was launched on Sunday at the opening ceremony of the 2026 World Conference on Science Literacy in Beijing.The organization is an international scientific and technological organization initiated with the support
AC Milan vs Lecce – Predicted lineup and team news
AC Milan will aim to keep their perfect, unbeaten run alive in Serie A this campaign as they host Lecce at the San Siro on Sunday, in what is their last outing before the international break arrives.T...
‘2 Broke Girls' Star Posts Hilarious Message 15 Years After Hit CBS Show Debuted
15 years later, Kat Dennings looks back on '2 Broke Girls' with a hilarious message.
Ed Sheeran Cries Alone Onstage in Philadelphia: 'I Am Making Mistakes. I'm So, So Sorry. I Don't Want to...
Protesters gathered outside the venue as he addressed Gaza directly for the first time.
1966 Rock Song, Written by Paul Simon, Was a 'Vicious' Dig at Bob Dylan
Years later, the iconic musicians ended up touring together.
Ed Sheeran Makes Huge Change to 'Loop Tour' Amid Macklemore Controversy
Ed Sheeran's Loop Tour looked very different from what fans may have expected when the singer-songwriter took to the stage in Philadelphia.
1985 Rock Song, Turned Down by Billy Idol, Became a Career-Defining No. 1 Hit
Before Simple Minds scored their No.
Health officials warn of potential measles exposure at Philadelphia Airport
Health officials are warning travelers of a possible measles exposure at Philadelphia International Airport last week, unrelated to recent exposures reported at Children's Hospital of Philadelphia.
There was a possible measles exposure at Philadelphia International Airport
The city department of public health is notifying travelers and others of the possible exposure, which is unrelated to the recent measles exposures at the Children’s Hospital of Philadelphia.
Bueckers, Wings handle business vs. Mercury to mark end of an era at College Park Center
ARLINGTON, Texas - The Dallas Wings have two more regular-season games remaining and a playoff run a...
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.
Possible measles exposure reported at Philadelphia International Airport not related to CHOP case
Editorial | China must enforce high standards of integrity for scientists
Beijing’s ambitions for scientific leadership require not just investment but trust from the international community and the Chinese public.
Phila. health officials warn of possible measles exposure at Philadelphia International Airport
The Philadelphia Department of Public Health is warning travelers about a possible measles exposure at Philadelphia International Airport.
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...
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.
Frontier Restaurant CEO donates $250,000 to UNM business school
Shannon Rainosek’s gift will support internships, competitions, conferences and international travel for UNM students.
Frontier Restaurant CEO donates $250,000 to UNM business school
Shannon Rainosek’s gift will support internships, competitions, conferences and international travel for UNM students.
Oscar Health (OSCR) Bets On Lucy As CEO Calls Time On Employer Coverage
Oscar Health (NYSE:OSCR) introduced its AI-driven Lucy Healthcare Marketplace, a digital hub for carriers, brokers, and consumers. The company presented Lucy as part of a shift toward individual coverage options, including support for ICHRA-based benefit designs. Chief executive Mario Schlosser said the traditional employer-sponsored health insurance structure is ending, pointing to alternative coverage models. Oscar Health’s Lucy Healthcare Marketplace launch and public push toward...
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.
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.
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.
Three Cuban women, three businesses, one dream: How they’re building their future in Miami
They arrived in Miami by different paths. Now they’re turning what they know and love — pole dancing, tennis and skin care — into businesses and a shot at the American dream.
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.
Chris Simms Eviscerates ESPN, 'College GameDay' For Political Propaganda
He didn't hold back.
M6 Pro Chip Result on Geekbench is Likely Fake
A supposed Geekbench result for an unreleased M6 Pro chip surfaced this week, but it is likely fake. Geekbench creator John Poole informed MacRumors that he uncovered "internal inconsistencies" that lead him to believe that the M6 Pro result might not be legitimate. Geekbench creator John Poole informed MacRumors that he uncovered "internal inconsistencies" that lead him to believe that the M6 Pro result might not be legitimate.
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.
Millions of funds from Rural Health Transformation program earmarked for Coast efforts
Mississippi is awarding more than $104 million to modernize and expand rural healthcare. The funding is part of the state’s Rural Health Transformation Program. George County is receiving multiple awards for hospital and healthcare upgrades, including new patient monitoring, lab and maternal health equipment, cybersecurity improvements, and other technology. Memorial Health System is also receiving millions for projects in Stone...
Fulham vs Manchester United predictions: Premier League tips and odds
Both Fulham and Manchester United are already under pressure this season ahead of their meeting at Craven Cottage on Sunday (kick-off, 4.30pm), in the final Premier League fixture before the international break.
Iconic 40-year-old beer brand closing down its beloved brewery
One of the first brewpubs to open in the U.S.
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. 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