The Fitness Scientist: "Even A Little Alcohol Is Hurting Your Health!" Kristen Holmes

1. 0:00 – 2:13

   Intro

   1. KHKristen Holmes0:00

      What the research says is that people who are having sex within a few hours of when they sleep have better markers of sleep and recovery.

   2. SBSteven Bartlett0:07

      So, does masturbation not have the same implications?

   3. KHKristen Holmes0:09

      Well, what was so interesting about this research is that-

   4. NANarrator0:12

      Kristen Holmes is the vice president of Performance Science at WHOOP. ... who has access to health data from hundreds of thousands of people, and her groundbreaking research will tell you the secrets of achieving perfect health and performance.

   5. KHKristen Holmes0:24

      The key to your health is your circadian rhythm, which are physical, mental, and behavioral changes that happen in a 24-hour cycle. One of the most known circadian rhythms is being asleep during the night, and it has massive health consequences. For example, we know that shift workers, on average, are going to die 15 years sooner, but if you're awake for two hours between 10:00 PM and 4:00 AM two days per week for 25 days of the year, you qualify as a shift worker. You are putting yourself at increased risk for cancer, cardiovascular disease. Mental health issues, can have trouble having children.

   6. SBSteven Bartlett1:00

      I mean, that's terrifying.

   7. KHKristen Holmes1:01

      We know that we haven't adapted to blue light.

   8. SBSteven Bartlett1:04

      The light we get from screens?

   9. KHKristen Holmes1:05

      Yes. If you're viewing light between the hours of 10:00 PM and 4:00 AM, it actually has a pro-depressive effect. The list goes on and on. And a lot of people are like, "I have to go to bed at 1:00 AM because I'm a night owl." Total BS. You're making a choice, and if you wanna perform consistently, increase your tolerance for stress and take control of your life, you need to-

   10. SBSteven Bartlett1:24

       We wanna eat.

   11. KHKristen Holmes1:25

       And most importantly, we need to-

   12. SBSteven Bartlett1:29

       Quick one. This is really, really fascinating to me. On the backend of our YouTube channel, it says that 69.9% of you that watch this channel frequently over the lifetime of this channel haven't yet hit the subscribe button. I just wanted to ask you a favor. It helps this channel so much if you choose to d- subscribe. Helps us scale the guests, helps us scale the production, and it makes the show bigger. So if I could ask you for one favor, if you've watched this show before and you've enjoyed it and you like this episode that you're currently watching, could you please hit the subscribe button? Thank you so much, and I will repay that gesture by making sure that everything we do here gets better and better and better and better. That is a promise I'm willing to make you. Do we have a deal?

2. 2:13 – 2:48

   Why do you do the work you do?

   1. SBSteven Bartlett2:13

      Kristen, why do you do the work that you do?

   2. KHKristen Holmes2:19

      I am, uh, irrationally passionate (laughs) about human flourishing and the frameworks, policies, basically determinants of, of human flourishing. And, um, yeah, I've kind of dedicated my life to understanding, um, how the physiology and, and psychology work together to help people take control of their health, um, so they can understand how to apply their e- energy and, and attention in a way that's truly rewarding.

3. 2:48 – 5:03

   What your work is and involves

   1. KHKristen Holmes2:48

   2. SBSteven Bartlett2:48

      What is your job title?

   3. KHKristen Holmes2:50

      I'm the vice president of Performance Science, principal scientist at, uh, WHOOP, which is a technology, a physiological monitoring technology company.

   4. SBSteven Bartlett2:57

      And what does that mean?

   5. KHKristen Holmes2:59

      So I'm trying to make sure, uh, WHOOP is a thought leader in human performance, so trying to see around the bend to understand, you know, what's gonna be important for tomorrow in terms of understanding, uh, how we can take control of the trajectory of our health. You know, what are the markers that are important that we need to be tracking? Um, what are the behaviors that we need to be engaging in in order to move those metrics around in a way that is health promoting? I look at a lot of the high stakes, high stress environments, so professional athletes, um, frontline healthcare clinicians, um, and, uh, you know, military operators. So kind of understanding some of these extreme professions and, and crafts and, and what the physiology and the psychology looks like. We can then kind of abstract and, and, and I think in some ways generalize what that means for the regular population, um, who are experiencing less extreme demands on, on their time and their energy and, and their cognitive bandwidth.

   6. SBSteven Bartlett3:58

      And do you conduct, um, your own studies?

   7. KHKristen Holmes4:01

      Yes. Yeah. So I'm a principal investigator on, um, on many studies, um, which means that I'm kind of leading those experiments from kind of A to Z, and I have a team that is, you know, kind of supporting that research, um, in f- various aspects of, of expertise. Um, but yeah, I mean, one of the studies that we published in, in May was looking at, uh, a thousand paratroopers in Army Alaska, so super extreme, you know, (laughs) environment-

   8. SBSteven Bartlett4:25

      Wow.

   9. KHKristen Holmes4:25

      ... you know, it's harsh, but the, the Army came to us. They were, you know, if, if you under- you know, Alaska in general has a very high suicide rate. Um, this base in Elmendorf, Ak- Alaska has a lot of mental health issues, a lot of suicide, and, um, they're trying to understand, you know, what is actually going on here. And we were able to run a study where we showed that there's actually one behavior, one behavior that was surfaced that was the most predictive of positive psychological functioning in these, um, in these soldiers, and that one behavior was sleep-wake timing.

4. 5:03 – 10:16

   The Importance Of Sleep Wake Timing - circadian rhythm

   1. KHKristen Holmes5:03

      So the more consistent and more stable the sleep-wake, the sleep onset and offset of these soldiers, um, the higher levels of positive psychological functioning, so workli- place resilience, um, uh, less homesickness, more feelings of control, more positive social networks. It bubbles up in every single piece of, of research that we do at WHOOP. Sleep-wake timing, I think, is the mother of all performance optimization behaviors.

   2. SBSteven Bartlett5:34

      Sleep-wake timing.

   3. KHKristen Holmes5:35

      Mm-hmm.

   4. SBSteven Bartlett5:36

      So is this the same thing as your circadian rhythm, or is it-

   5. KHKristen Holmes5:38

      Yeah. So this is one of the most, I think when we think about circadian rhythms, which is just physical, mental, and behavioral changes that happen in a 24-hour cycle, um, and your biological clock is kind of orchestrating these rhythms, right? And-

   6. SBSteven Bartlett5:54

      Okay, so I'm gonna have to s- pause-

   7. KHKristen Holmes5:55

      Yep.

   8. SBSteven Bartlett5:55

      ... and take this right back to, uh, monkey level stuff.

   9. KHKristen Holmes5:58

      Yeah.

   10. SBSteven Bartlett5:59

       What is a circadian rhythm?

   11. KHKristen Holmes6:00

       So-

   12. SBSteven Bartlett6:00

       As if you were explaining it to a 10-year-old.

   13. KHKristen Holmes6:01

       Yeah. So it's basically physical, mental, and behavioral changes-... that happen over a 24-hour cycle.

   14. SBSteven Bartlett6:12

       Okay. So here's my read on it and correct me if I'm wrong.

   15. KHKristen Holmes6:17

       Mm-hmm.

   16. SBSteven Bartlett6:17

       There's a clock-

   17. KHKristen Holmes6:19

       Hmm.

   18. SBSteven Bartlett6:20

       ... in my head.

   19. KHKristen Holmes6:21

       Yes. The, the, the suprachiasmatic nucleus-

   20. SBSteven Bartlett6:25

       Yeah.

   21. KHKristen Holmes6:25

       ... is the, is the master clock.

   22. SBSteven Bartlett6:27

       Okay, which is somewhere in my body.

   23. KHKristen Holmes6:29

       It's in the, it's in the hypothalamus.

   24. SBSteven Bartlett6:31

       So it's in my brain?

   25. KHKristen Holmes6:32

       Yes.

   26. SBSteven Bartlett6:32

       And this clock regulates every cell in my body?

   27. KHKristen Holmes6:35

       Cell, tissue, organ.

   28. SBSteven Bartlett6:37

       Okay. And it releases, it controls the release of a chemical which makes those cells, organs, every part of my body do stuff?

   29. KHKristen Holmes6:48

       Yeah. So it is your hypothalamus, so the suprachiasmatic nucleus, it responds to light and it responds to darkness.

   30. SBSteven Bartlett6:56

       Okay.
5. 10:16 – 15:07

   Humans Haven't Adapted For Artificial Light

   1. SBSteven Bartlett10:16

   2. KHKristen Holmes10:16

      Right.

   3. SBSteven Bartlett10:16

      ... et cetera, et cetera.

   4. KHKristen Holmes10:17

      Your body loves regularity and, and that's, and the problem is modernity is not set up for, uh, that. You know, we have access, you know, I think all the circadian research, um, unfortunately was done after the advent of electric, you know, electricity. So, so we're kind of fighting, you know, this access to constant light. Um, and, you know, we're starting to see the, the, I think deleterious effects or the, the negative consequences of exposure to light really after the sun goes down. We haven't adapted to blue light after dark, right? After the sun goes down. We have not adapted to blue light.

   5. SBSteven Bartlett10:57

      Blue light being the light we get from screens.

   6. KHKristen Holmes10:58

      Yes. There is a study that looked at the timing of light and its impact on, um, mood and, and brain circui- circuits and they saw that if you're viewing light between the hours of, again, this is kind of this magic window of time, 10:00 PM and 4:00 AM, it actually has a pro-depressive effect. So it impacts your dopamine system, reward, motivation, right? So when we wonder, you know, oh, why are, why, what is this mental health crisis? I mean, we have to look at light first. And I, and I just don't know and, and I think what's hard about the discussion and hard about this behavior is that, you know, it, it's really hard for people to not engage with their phones, you know, before bed. Um, that has its own addictive properties, right? But we just have to understand that these, our, our relationship to light will directly influence the trajectory of our health. There's just no question about that.

   7. SBSteven Bartlett12:00

      To understand this from a more sort of prehistoric ancestorial lens, if we go back, I don't know, tens of thousands of years to how maybe some of our ancestors used to live-

   8. KHKristen Holmes12:11

      Mm-hmm.

   9. SBSteven Bartlett12:11

      They would have food at certain times-

   10. KHKristen Holmes12:14

       Mm-hmm.

   11. SBSteven Bartlett12:14

       ... and they would have light exposure at certain times. They didn't have artificial light-

   12. KHKristen Holmes12:17

       Right.

   13. SBSteven Bartlett12:17

       ... they hadn't invented that yet. The modern world is very much the antithesis of that.

   14. KHKristen Holmes12:21

       It is.

   15. SBSteven Bartlett12:21

       We have food whenever we want it. We can order f- I can order a cookie at 3:00 AM if I wanna eat-

   16. KHKristen Holmes12:26

       Right.

   17. SBSteven Bartlett12:26

       ... a cookie at 3:00 AM, and I can watch a YouTube video-

   18. KHKristen Holmes12:29

       (laughs)

   19. SBSteven Bartlett12:29

       ... The Diary of a CEO, for example, like and subscribe, at any hour of the day. Um, so is this kind of like a misalignment issue with our, the way our body was designed by nature-

   20. KHKristen Holmes12:40

       Mm-hmm.

   21. SBSteven Bartlett12:41

       ... and the world we now live in?

   22. KHKristen Holmes12:42

       Yeah, we have not evolved to- to- to digest food in the middle of the night or- or to view light in the middle of the night, um, or to be super active in the middle of the night. We just haven't, and it does, it creates this, it creates this misalignment, and, you know, I think what's interesting if we are to kind of look at individuals, you know, or societies currently that don't have electricity, it's- it's really interesting to- to, I think, see some of their behaviors, some of their sleep/wake behaviors, and this is fascinating. There was a study done looking at, um, kind of a hunter/gatherer type of society who don't have access to any electricity, and when you observe their sleep/wake times, they all fall asleep within 15 to 30 minutes of each other, and they all wake up between 15 and 30 minutes of each other. So this whole notion of chronotypes is, like, kind of, like, total BS. It's like, 'cause I think that's, you know, I think that's the reason a lot of people are like, "Oh, I- I- I have to go to bed at 1:00 AM because I'm a night owl." No, you're- you're making a choice, generally speaking. Now, this is in healthy populations, not people who have circadian, you know, dis- disorders and- and things like that. Um, generally speaking, like if you were to throw everyone in this building on a mountain in Colorado, and this experiment has actually been done, with no electricity, we will literally all fall asleep within 30 minutes of each other after 48 hours. Like, that is how powerful these light/dark signals are to our body, and I- I think that just those two examples are really, uh, compelling in that, you know, we're, we have evolved to kind of wake up and fall asleep in relation to this light/dark cycle.

   23. SBSteven Bartlett14:20

       So all of this stuff we say to ourselves, 'cause I say that to myself as, all the time, I told, I've told myself I'm a- a night owl.

   24. KHKristen Holmes14:25

       Yeah.

   25. SBSteven Bartlett14:25

       And I've given myself the whole chronotype spiel.

   26. KHKristen Holmes14:27

       Yeah.

   27. SBSteven Bartlett14:28

       That's BS.

   28. KHKristen Holmes14:29

       Yeah. Uh, in my opinion, the way I interpret the literature, it- it seems that, you know, the- the variability that I think is talked about or how we think about it in a, as a, as a society in terms of there's chronotypes that are, you know, very fr- you know, you're, you fall asleep, you wanna, you, you're genetically predisposed to fall asleep at 1:00 AM and I'm genetically predisposed to- to fall asleep at 9:00 PM, yeah, I don't- I don't think it's that kind of variability. I think the variability maybe is an hour at the most, maybe an hour and a half. Obviously there's, it's age-related as well, um, but for the most part, I don't, I don't think this variability is- is as pronounced as- as- as what, um, as what we say it is.

6. 15:07 – 18:43

   The Myths Around The Hours Of Sleep You Get

   1. KHKristen Holmes15:07

   2. SBSteven Bartlett15:07

      Sleep.

   3. KHKristen Holmes15:08

      Yeah.

   4. SBSteven Bartlett15:08

      So conventional wisdom says it's all about how many hours you spend sleeping.

   5. KHKristen Holmes15:14

      Mm-mm. We already, this has already been shown to be not true. Sleep duration is- is important, right? We can put a pin in that. Um, but sleep regularity predicts all cause mortality, and this is just recently published actually, um, not by my team. But, um, looking at, it was actually UK, uh, uh, biobank, 60,000 people, ten million sleeps, objective measure of sleep, and they found that sleep regularity predicted, uh, mortality and independent of sleep duration. So it, it's not to say that sleep duration doesn't matter, but that is absolutely incomplete advice. How much time you spend in bed doesn't necessarily predict how long you live. It is the degree to which you stabilize when you go to bed and when you wake up that predicts mortality.

   6. SBSteven Bartlett16:06

      What did they find? What were the, what was the conclusion about it? Was there a, sort of a percentage variance in those-

   7. KHKristen Holmes16:11

      So-

   8. SBSteven Bartlett16:11

      ... that had irregular and regular sleep?

   9. KHKristen Holmes16:13

      Yeah, so the sleep onset/offset times, I'm- I'm not sure, but actually this is research that my team is doing and that we have not published yet, so this is preliminary data, but we are, we are actually able to determine down to the minute what is a tolerable level of variability. So for the most elite athletes on the planet, the 0.001%, 18 to 23 year olds, we know that, um, 70 minutes of onset/offset variability, at 70 minutes, we will see a sharp decline in markers of recovery, heart rate variability, resting heart rate, which is a indicator of how you will adapt to load the next day.

   10. SBSteven Bartlett17:01

       To stress the next day.

   11. KHKristen Holmes17:02

       To stress the next day.

   12. SBSteven Bartlett17:03

       Okay.

   13. KHKristen Holmes17:03

       So life load. So sleep/wake time is really important, and we're- we're- we're doing research across- across every age bucket and- and but you can imagine that if these are the most robust humans on the planet and they have 70 minutes of- of variability that is tolerable, within that population, some are a little bit sooner, um, in terms of the, or, uh, can deal with less variability and others can deal with slightly more variability, but the mean is 70, 70 minutes. So you can imagine for individuals who are more vulnerable, who have less, are less robust physically, mentally, emotionally, their tolerable level is gonna be much narrower.

   14. SBSteven Bartlett17:46

       What's going on inside of the body when we increase the variability or that we don't have a regular sleep and a regular wake-up time?

   15. KHKristen Holmes17:55

       Mm-hmm.

   16. SBSteven Bartlett17:55

       What's actually going on from, like, a chemical/physiological perspective?

   17. KHKristen Holmes17:57

       Yeah, so one of the things that's suppressed is melatonin, and m- circulating, reductions in circulating melatonin have been shown to be linked to every disorder and disease in the body.... every disorder and disease in the body. When we have suppressed or reduced circulating melat- melatonin, that is gonna impact us on every level and make us more vulnerable to disease and, and disorders. So, that is probably one of the most important thing when we have super unstable sleep-wake time, we are going to, uh, have se- uh, suppressed melatonin production, um, which leads to inflammation in the body. It's melatonin, I think is, is one of the big

7. 18:43 – 20:08

   A Lack Of Sleep Is Hurting Muscle Growth

   1. KHKristen Holmes18:43

      players in this story.

   2. SBSteven Bartlett18:45

      Growth hormones.

   3. KHKristen Holmes18:46

      Yes. Yes. And, uh, typically be, you know, if you're not going to sleep, uh, if you're going to sleep late, you will not release, uh, human growth hormone, um, as, uh, you'll get less of a bolus of, of release.

   4. SBSteven Bartlett19:00

      And why does that matter?

   5. KHKristen Holmes19:01

      That's when all the physical restoration happens, so all the regeneration physically. So if we're bypassing that, we're basically, all the work that we did in the gym or, (laughs) you know, everything that we did during the day, um, we're just not gonna recover, um, from that in, in the same way that we would if we were getting that sleep.

   6. SBSteven Bartlett19:16

      Is growth hormone essentially the thing that causes our sort of muscles to grow and repair,-

   7. KHKristen Holmes19:20

      Yeah.

   8. SBSteven Bartlett19:20

      ... essentially? So-

   9. KHKristen Holmes19:21

      Yeah.

   10. SBSteven Bartlett19:21

       I sometimes think this 'cause I think if I'm ... Sometimes in my life because I'm quite busy, I have to make the decision whether to go to the gym or get a great night's sleep.

   11. KHKristen Holmes19:30

       Mm-hmm. Yeah.

   12. SBSteven Bartlett19:31

       And the more I've learned about growth hormone in the body and Whoop and all those things, I've started to make the decision towards sleep-

   13. KHKristen Holmes19:38

       Mm-hmm.

   14. SBSteven Bartlett19:38

       ... versus going to the gym because my brain now goes, "Well, you're not gonna get the recovery and r- sort of restoration anyway."

   15. KHKristen Holmes19:44

       Yeah, the benefits.

   16. SBSteven Bartlett19:44

       Yeah,-

   17. KHKristen Holmes19:44

       Yeah.

   18. SBSteven Bartlett19:44

       ... the benefits of going to the gym if you're poorly slept that night.

   19. KHKristen Holmes19:48

       Yep. I, I think if it's, um, if you're consistently getting, you know, decent sleep and consistently getting, you know, going to bed and wake up, you sleep more times, um, you know, I would say it's okay to prioritize exercise sometimes. Um, but sleep is, is very important (laughs) um, and is probably the thing that needs to be

8. 20:08 – 25:23

   A Solid Sleeping Pattern Can Prevent Sickness

   1. KHKristen Holmes20:08

      prioritized first.

   2. SBSteven Bartlett20:10

      How consistent are you with your sleep?

   3. KHKristen Holmes20:12

      I'm very consistent.

   4. SBSteven Bartlett20:14

      I heard that in 2017 you started trying to sleep within sort of 25 to 30 minutes-

   5. KHKristen Holmes20:19

      Mm-hmm.

   6. SBSteven Bartlett20:20

      ... um, every single day.

   7. KHKristen Holmes20:21

      Yep.

   8. SBSteven Bartlett20:21

      The same sleeping window.

   9. KHKristen Holmes20:22

      That's right. Yeah, and-

   10. SBSteven Bartlett20:24

       Okay.

   11. KHKristen Holmes20:24

       ... yeah, it was a, it was a paper that came out, uh, by Andrew Phillips actually in, in the summer of 2017, and it basically was a four-year study, um, that was conducted at Harvard University looking at students and they were basically s- student sleep and they were trying to see, okay, you know, what aspect of, of sleep is, is predictive of things like GPA and, um, other, uh, you know, measures of, of kind of, uh, flourishing. And, uh, (laughs) what they found is that basically sleep-wake time predicted GPA. (laughs)

   12. SBSteven Bartlett20:55

       What's GPA for people who are-

   13. KHKristen Holmes20:56

       Which is a ... Oh, sorry, grade point average. Yeah, so it's the difference, you know, the more regular, you know, it's the difference between getting an A and a B, um, by just stabilizing sleep-wake time. And so, at that time, I was working with, you know, tons of collegiate athletes, so NC2A athletes, professional athletes, so EPL, um, you know, NBA, NFL, MLB, y- you name it, like, the biggest high performers, like, in the world. And, and w- I started tracking this, you know, just manually. W- at the time, at Whoop, we didn't actually track this, uh, this wasn't automated. I had to like, you know, to kind of do this in Excel. And then sure enough, you know, sleep-wake time started predicting all these performance metrics that people care about. And, um, we started rolling in some subjective measures, um, we had internal load, we had external load, of course, so all these obj- objective measures, but I started rolling in some subjective measures, and sure enough, sleep-wake time just continued to, to, to ladder up to all these performance variables that people care about. So, I started, of course, (laughs) you know, 'cause I have access to all of these, these data, I start, I'm like, "Shit, I need to," (laughs) "I need to like start stabilizing my sleep-wake time." And sure enough, summer 2017, I just like, that's basically like my non-negotiable, and yeah, I mean, I, I haven't, I haven't been sick since 2017. I had a little tiny head cold that lasted 48 hours, but since then, I literally have not had a sniffle, a stomach ache. I didn't get COVID. Like, uh, I literally have not been sick. And, you know, there, I do a lot of other things well, but that has been the single biggest change.

   14. SBSteven Bartlett22:35

       Just sleeping and waking up at the same time?

   15. KHKristen Holmes22:37

       That's it.

   16. SBSteven Bartlett22:38

       What is your routine now? How do you ensure that happens because-

   17. KHKristen Holmes22:40

       Yeah, so the, the key to that is stabilizing when I wake up. So even when I travel, and I do travel, and I, I travel internationally, I travel to the West Coast, um, I try to maintain my home time zone as much as I can, as long as I can fulfill my business commitments and, and social, you know, there might be a social element as well, but for the most part, um, I stabilize when I wake up. So, I keep that consistent. Even if I can't go to bed at the same time, I ensure that I wake up at the same time. And that basically sets my circadian rhythm so I will then feel sleepy at the right time and I can kind of keep that virtuous cycle going. If I, um, have short sleep, I just basically try to build in a nap prior to 1:30 for 30 minutes to an hour so I don't accumulate sleep debt. This is another thing (laughs) that we can talk about. Sleep debt is wild in some of its correlations like psychological safety and executive function and, um, but, but yeah, so I kind of, that's how I manage short sleep, um, but I, I always try to wake up at the same time, so I'm getting that bolus of light at the same time every single day.

   18. SBSteven Bartlett23:44

       And what time do you wake up and go to sleep?

   19. KHKristen Holmes23:46

       So I go to bed, um, around, I kinda get into bed usually around 9:15, 9:30. I read for a half an hour or 45 minutes, a book, um, printed page, dim light, (laughs) um, and then I fall asleep usually around 10:00, and then I wake up, um, like at 6:00, uh, 14 ... No, I'm just kidding. Like around 6:00.

   20. SBSteven Bartlett24:09

       (laughs)

   21. KHKristen Holmes24:09

       (laughs) Around 6:00.

   22. SBSteven Bartlett24:10

       You know, whenever I talk about these subjects, the rebuttal I get is one-

   23. KHKristen Holmes24:15

       Mm-hmm.

   24. SBSteven Bartlett24:15

       ... you might be able to predict.

   25. KHKristen Holmes24:17

       Oh.

   26. SBSteven Bartlett24:17

       It's from a group of people that I can't yet relate to.

   27. KHKristen Holmes24:21

       Yeah.

   28. SBSteven Bartlett24:21

       Do you know who I'm talking about?

   29. KHKristen Holmes24:23

       Um...

   30. SBSteven Bartlett24:23

       Parents.
9. 25:23 – 32:26

   The Best Times To Eat For The Perfect Sleep

   1. KHKristen Holmes25:23

      health and things like that.

   2. SBSteven Bartlett25:24

      So let's talk about that then.

   3. KHKristen Holmes25:26

      Mm-hmm.

   4. SBSteven Bartlett25:26

      Meal timing.

   5. KHKristen Holmes25:27

      Mm-hmm.

   6. SBSteven Bartlett25:28

      What is the ... What do I need to know about when I should be eating, what I should be eating, um, and, and the implications that has on-

   7. KHKristen Holmes25:34

      Yeah.

   8. SBSteven Bartlett25:34

      ... my circadian rhythm, my body clocks?

   9. KHKristen Holmes25:36

      Yeah. So it's, it's, in the literature, there's time-restricted eating and there's time-restricted feeding. Um, and time-restricted feeding generally, if you read in the literature, is gonna refer to mouse models. Time-restricted eating will refer to human, uh, studies.

   10. SBSteven Bartlett25:49

       Mouse models being studies they did with mice.

   11. KHKristen Holmes25:51

       Mouse, yeah, sorry. Um, yeah, mice, uh, studies done with, with mice are just time-restricted feeding. T- and, and humans would be time-restricted eating. And not to confuse this with intermittent fasting, which I know is a hot topic and people love talking about it, um, but time-restricted eating basically has a circadian component, so it's really about the timing of when you're eating your food in relation to the light-dark cycle. Intermittent fasting is basically just reducing calories. And so time-restricted eating does not have a calorie, um, uh, c- component to it. It's more about the, the timing. And there's been some, a lot of interesting studies, um, that have been done that show if you eat, you know, within, uh, you know, kind of 8 to 12 hour window, uh, you will have, uh, much better metabolic outcomes. And this is pretty- this is well established. Um, and I- and if- we see in the WHOOP data that if you're, um, if you stop eating three hours prior to when you sleep, to when you fall asleep, markers of sleep and recovery are, are, uh, exponentially better. Um, so timing of meals really, really does matter, and there's no question that, uh, and we, we know this from, from other research, you're more primed to metabolize food, um, closer to when you wake up in the morning. So earlier in the day, you're gonna be much more primed to utilize the, the nutrients that you're, um, that you've digested.

   12. SBSteven Bartlett27:24

       So does that mean we should be eating- we should have sort of an earlier eating window?

   13. KHKristen Holmes27:27

       Yes. Yes.

   14. SBSteven Bartlett27:29

       I- you know Brian Johnson.

   15. KHKristen Holmes27:30

       Of course, yeah.

   16. SBSteven Bartlett27:31

       Um...

   17. KHKristen Holmes27:31

       I know he stops eating at 11:00 AM.

   18. SBSteven Bartlett27:32

       Which is crazy.

   19. KHKristen Holmes27:33

       So, which is insane and not super practical, but I think if you can stop eating around when the sun sets, you'll position yourself to improve your metabolic health. And I, and I would go so far to say that, you know, regardless of what it is you're eating, s- 'cause a lot of folks cannot afford to, you know, eat high quality food. That's just a reality. And a lot of those folks do suffer from, you know, higher rates of cardio-metabolic dysfunction. But if, if we can just consolidate our eating window to 8 to 10 hours, we get ourselves like 60% of the way to our, our kind of metabolic goals. Again, it's not to say that content and quality does not matter. It absolutely does, but if we aren't gonna- if, if we, if we can't focus on that for whatever it might be, consolidating our eating window, so eating every single one of our calories between, you know, an 8 to 12 hour window, we will improve our health.

   20. SBSteven Bartlett28:32

       And what's your eating window?

   21. KHKristen Holmes28:33

       So, I do about 10 hours.

   22. SBSteven Bartlett28:35

       Okay.

   23. KHKristen Holmes28:35

       Yeah. So I, I definitely, I pretty much don't eat after the sun goes down.

   24. SBSteven Bartlett28:40

       When you say the sun goes down...

   25. KHKristen Holmes28:42

       Mm, sun sets, yeah.

   26. SBSteven Bartlett28:43

       Is that like 5:00 PM?

   27. KHKristen Holmes28:45

       I mean, now it's early, yeah.

   28. SBSteven Bartlett28:47

       Right.

   29. KHKristen Holmes28:47

       So I give myself like an hour-

   30. SBSteven Bartlett28:48

       4:00 PM.
10. 32:26 – 34:09

    The Positive and Negative Effect Of Exercise On Our Sleep

    1. KHKristen Holmes32:26

    2. SBSteven Bartlett32:26

       Exercise.

    3. KHKristen Holmes32:27

       Mm-hmm.

    4. SBSteven Bartlett32:28

       One of the issues that I have sometimes in my life, a- today is one of those days, where, because I was up very early this morning-

    5. KHKristen Holmes32:34

       Mm-hmm.

    6. SBSteven Bartlett32:34

       ... it meant that I didn't go to the gym this morning, which means I'm probably gonna get home after being in the studio, being in the office today-

    7. KHKristen Holmes32:42

       Mm-hmm.

    8. SBSteven Bartlett32:42

       ... at maybe 7:00, 8:00 PM.

    9. KHKristen Holmes32:44

       Mm-hmm.

    10. SBSteven Bartlett32:44

        And I'm super hungry then-

    11. KHKristen Holmes32:46

        Yeah.

    12. SBSteven Bartlett32:46

        ... usually, right?

    13. KHKristen Holmes32:47

        Yeah.

    14. SBSteven Bartlett32:47

        And I also need to work out. So sometimes what happens is I choose to work out first and then obviously the- it makes the meal late at night, but there's also days in my life where I end up working out, and I'm known for this-

    15. KHKristen Holmes32:57

        Mm-hmm.

    16. SBSteven Bartlett32:57

        ... at like 11:00 or 12:00 PM at night.

    17. KHKristen Holmes32:59

        Wow.

    18. SBSteven Bartlett33:00

        And (sighs) there was this old train of thought that that was a good thing to do because people would say, "Oh, you're gonna be tired when you get in bed." But that doesn't seem to be what happens.

    19. KHKristen Holmes33:11

        Yeah. Does it, do you feel more energized?

    20. SBSteven Bartlett33:13

        I feel more energized.

    21. KHKristen Holmes33:14

        Yeah. Well, not surprising, right? You know, adrenaline, cortisol, like all of the kind of hormones and chemicals that you need to kind of get to a place where you can exert that energy are, are kind of flowing through the system and it takes time for them to go back to, to normal levels, so to kind of get back to homeostasis is gonna take some time. And, and so, yeah, I mean, it would make sense that you're, um, you know, kind of activated, um, after exercise. So for some folks, there is a lot of individual variability, I think, with exercise timing. Some people are impacted more. But I honestly think that it has more to do with the light. You know, usually if we're in a gym it's generally well lit, right? You're not in a dark gym, so you're getting exposure to, um, to light, which is gonna make you feel, like, more activated, and it's again, telling your body that it's time to be awake

11. 34:09 – 36:32

    The Importance Of Getting Sunlight When We Wake Up

    1. KHKristen Holmes34:09

       and alert.

    2. SBSteven Bartlett34:10

       On that point of light, there's a school of thought that says you should look at lights when you wake up in the morning.

    3. KHKristen Holmes34:16

       Mm-hmm.

    4. SBSteven Bartlett34:17

       My, my partner always-

    5. KHKristen Holmes34:17

       Great.

    6. SBSteven Bartlett34:17

       ... gets up in the morning, walks out into the balcony and sits out there for 10 or 20 minutes in the morning.

    7. KHKristen Holmes34:20

       Oh, my gosh, I love that. Yes, I love to hear that. (laughs)

    8. SBSteven Bartlett34:23

       Yeah, she's the best. You know, it's just so annoying.

    9. KHKristen Holmes34:25

       (laughs)

    10. SBSteven Bartlett34:25

        She gets everything right.

    11. KHKristen Holmes34:26

        Ugh. Love it.

    12. SBSteven Bartlett34:28

        Um...

    13. KHKristen Holmes34:28

        Yeah. But, but for sure, that you wanna get light within, you know, 100,000 lux is, is pretty much what you wanna get within, you know, five to 20 minutes of waking up to tell your body, like, it's time to go.

    14. SBSteven Bartlett34:40

        100,000 what?

    15. KHKristen Holmes34:41

        Oh, lux. So just, like, photon energy. So pre- pretty much if you're outside for five to, to 20 minutes, and it sounds like your girlfriend is, like, nailing this protocol, you'll get all of the photon energy that you need to tell your system that it is time to be awake.

    16. SBSteven Bartlett34:58

        Can't you just go look into a lamp or something?

    17. KHKristen Holmes35:00

        Um, it will just take longer because it doesn't have the same light intensity. But if you're waking up, you know, prior to when the sun gets up, yeah, turn on the lights, you know, you wanna try to mimic day as much as possible, and then once the sun does come up, it's good to get outside.

    18. SBSteven Bartlett35:14

        And before you get in bed, you, you, you reference that you read w- books versus being on an iPad-

    19. KHKristen Holmes35:19

        Yes.

    20. SBSteven Bartlett35:19

        ... or screens, et cetera.

    21. KHKristen Holmes35:21

        Mm-hmm.

    22. SBSteven Bartlett35:23

        Um, does the same philosophy and principle apply to light exposure before sleep as to food exposure before sleep?

    23. KHKristen Holmes35:31

        Oh, no question. Right, absolutely. Um, we wanna try to restrict light basically after the sun goes down. We wanna dim our home environment to the degree that we can. Um, we wanna try to minimize all artificial light in the lead-up to bed.

    24. SBSteven Bartlett35:45

        All artificial light?

    25. KHKristen Holmes35:46

        Yes. Yeah. You wanna make it as d- dim as possible, so you know, there are a lot of night, like blue light blocking glasses, the filters that you can put on your iPad and your phone, activate all of those, um, but, but again, like, we don't... We wanna protect our melatonin release, right? And, and for all the reasons I k- kind of have explained. When we don't have it is linked to every disease and disorder, right? So we, we know this. So we wanna protect our melatonin release, and the only way we can release melatonin is by darkness. We, we need to be exposed to, to darkness in order for that master clock in our brain to know that it's time to go to sleep, um, and again, be able to tell our body, our tissues and organs and, and cells and our, and our body what

12. 36:32 – 39:20

    Things To Do For A Perfect Night's Sleep

    1. KHKristen Holmes36:32

       it needs to do at that moment.

    2. SBSteven Bartlett36:33

       When I was at the Whoop headquarters in Boston, um, not so long ago, I saw them working on sleep masks.

    3. KHKristen Holmes36:39

       Mm-hmm.

    4. SBSteven Bartlett36:39

       And I think I've always been quite dubious about sleep masks. Like, you know, you get on those planes and they hand you a sleep mask in a little bag.

    5. KHKristen Holmes36:45

       Mm-hmm.

    6. SBSteven Bartlett36:45

       I always thought, "What a bunch of weirdos." You know, like putting that-

    7. KHKristen Holmes36:48

       (laughs)

    8. SBSteven Bartlett36:48

       ... strapping that thing to your face.

    9. KHKristen Holmes36:49

       Yeah.

    10. SBSteven Bartlett36:49

        How embarrassing. I'm one of those weirdos now.

    11. KHKristen Holmes36:53

        Yeah. I mean, it's hard. Even the little dot on your... you know, from your alarm clock or your TV-

    12. SBSteven Bartlett36:59

        Yeah.

    13. KHKristen Holmes36:59

        ... is gonna emit enough light. We're so sensitive to light.

    14. SBSteven Bartlett37:04

        Hmm.

    15. KHKristen Holmes37:05

        Artificial light. So natural light, like the moon, totally fine, but any other type of light is really gonna impair our ability to get into these deeper stages of sleep where all the restor- restoration and regeneration happens.

    16. SBSteven Bartlett37:18

        Do you use a sleep mask?

    17. KHKristen Holmes37:19

        I do, yes.

    18. SBSteven Bartlett37:21

        What's your sort of routine there?

    19. KHKristen Holmes37:23

        Um, yeah, just when I start to feel sleepy, I just put it on and go to bed.

    20. SBSteven Bartlett37:28

        Do you listen to anything when you go to sleep?

    21. KHKristen Holmes37:30

        No. I don't.

    22. SBSteven Bartlett37:32

        Is there... Are you aware of any research that might indicate that listening to serial killer documentaries-

    23. KHKristen Holmes37:38

        (laughs)

    24. SBSteven Bartlett37:38

        ... at 3:00 A.M. (laughs)

    25. KHKristen Holmes37:40

        I think, in principle-

    26. SBSteven Bartlett37:41

        (laughs)

    27. KHKristen Holmes37:41

        ... anything that activates you, uh, stimulates you cognitively or, um, makes you energized, you probably wanna avoid reading. Yeah.

    28. SBSteven Bartlett37:52

        Interesting.

    29. KHKristen Holmes37:53

        Mm-hmm.

    30. SBSteven Bartlett37:53

        The... I think there's a group of us out there, I'm yet to meet them, but I, but I know that I'm not alone, that like to listen to horror and thriller and serial killer stuff at, um, you know, very late at night.
13. 39:20 – 45:14

    A Message For People That Aren’t Taking This Information Seriously

    1. KHKristen Holmes39:20

    2. SBSteven Bartlett39:20

       There's a huge group of people who listen to podcasts like this-

    3. KHKristen Holmes39:24

       Mm-hmm.

    4. SBSteven Bartlett39:24

       ... and as they listen to these podcasts, they just feel more depressed about their situation.

    5. KHKristen Holmes39:28

       Mm-hmm.

    6. SBSteven Bartlett39:29

       You know, because they've... They believe they're trying their very best and they're still struggling, especially as it relates to sleep. I think... I've always wondered what the message one can send to them. And also, do you know, I think there is a huge component of sort of personal responsibility and choice that you speak about as well, and that I believe in as well. But what is the most compelling message for those people that do have a choice?

    7. KHKristen Holmes39:55

       Mm-hmm.

    8. SBSteven Bartlett39:55

       They, they know deep inside-

    9. KHKristen Holmes39:57

       Mm-hmm.

    10. SBSteven Bartlett39:57

        ... much of it is a lack of discipline.

    11. KHKristen Holmes39:59

        Yeah.

    12. SBSteven Bartlett39:59

        They know they could not watch YouTube. They know they could put their phone away at 9:00 PM. They know they could not eat the cookie super late at night.

    13. KHKristen Holmes40:05

        Mm-hmm.

    14. SBSteven Bartlett40:05

        They know they could ch- Deep down, they know they could make a different set of choices, but they listen to these podcasts over and over again, whenever I have the health experts on, and maybe they even take notes, but they just don't do it.

    15. KHKristen Holmes40:16

        Yeah.

    16. SBSteven Bartlett40:17

        What is the most compelling thing you can say to those people that do have a choice, but continually choose a bad option to get them pushed over the fence to the positive circadian rhythm-

    17. KHKristen Holmes40:32

        Mm-hmm.

    18. SBSteven Bartlett40:32

        ... body clock loving side?

    19. KHKristen Holmes40:35

        Yeah, so if people are trying to develop new habits, you have to understand how that new habit links to your values. So the things that you believe in, the things that you say you care about, right? If I know growth and impact are my two most important values, presence is another one, how... What do I need to do every single day to back into that so I can align my behaviors with the things I say I care about? And I think when folks are struggling, um, they don't really know who they wanna be in the world and they don't maybe understand exactly what it is that they value. They're fuzzy-

    20. SBSteven Bartlett41:17

        Hmm.

    21. KHKristen Holmes41:17

        ... about their desires, about their values. And I think you end up, when you're fuzzy about your desires and the things that you value, you end up, you're flinging yourself in all sorts of directions, emotionally, physically, mentally, right? And, and I think that's kind of the project is figure out what you care about and then align your behaviors and create outlets in your life. And that, frankly, might mean getting rid of people, (laughs) you know, who don't support those values. A- and I think we're way too lenient on our circle of friends, um, in, in the sense of, you know, I think we, we keep people around in our life who don't ne- necessarily help us become a better version of ourselves.

    22. SBSteven Bartlett42:05

        Have you had to shed some people?

    23. KHKristen Holmes42:07

        Yes.

    24. SBSteven Bartlett42:09

        Why?

    25. KHKristen Holmes42:09

        Absolutely.

    26. SBSteven Bartlett42:11

        Why did you shed them?

    27. KHKristen Holmes42:13

        Because it, it didn't really support who I wanted to be.

    28. SBSteven Bartlett42:17

        Who did you want to be?

    29. KHKristen Holmes42:18

        Um, I wanted to be able to wake up at a very simple level with as much joy and energy as I, as I could, and I, and I wanted to be present for my kids, and, um... Yeah, so...And, and, and, so I- I think, and, and I think folks are engaging in behaviors that's, um ... (pauses) K- I, I think, you know, create, um, a situation where ... Yeah, I don't know how to say this without, like ... (laughs)

    30. SBSteven Bartlett42:58

        Just say it.
14. 45:14 – 51:54

    Growing Up With Addiction

    1. KHKristen Holmes45:14

    2. SBSteven Bartlett45:14

       When I talk about being able to change your behavior and break a habit, it is nothing in the context of someone who is ensnared by an addiction of sorts. It is not- it- it's a completely different conversation.

    3. KHKristen Holmes45:30

       Yeah.

    4. SBSteven Bartlett45:31

       What is it like growing up with a mother who you observe, at a very young age ... You were how old?

    5. KHKristen Holmes45:38

       I mean, my whole life.

    6. SBSteven Bartlett45:40

       Your whole life?

    7. KHKristen Holmes45:40

       Yeah. Like, she ... Mm-hmm.

    8. SBSteven Bartlett45:42

       As a child, when you- when you see a parent, someone you love, that is in- that is sort of gripped by addiction, what is that like?

    9. KHKristen Holmes45:53

       Yeah, I mean, I think at a- at a fundamental level, um, you just feel deprioritized, I think, generally. You know, like you- you know, I th- I think you feel, um ... You know, you're- you're- you're unsupervised, number one. There isn't a lot of supervision, you know? (laughs) So you end up, like, really having to- to fend for yourself. Um, my dad worked a lot, you know, he was definitely a workaholic, um, th- such a good man, um, so much integrity, and- and- but I think that was his form of escape, but it kind of leaves, you know ... You gotta figure out how to eat, you gotta (laughs) you know- you know, you gotta figure out how to do a lot of the basic stuff on your own. So, you develop a lot of independence, I think, but it- it's hard to, um, you know, form emotional attachments, I think, um, as an adult unless you really work through that. (laughs) You know, because you're- you're afraid that you're not gonna be taken care of.

    10. SBSteven Bartlett46:58

        What did you come to understand about your mother's addiction, and what she was struggling with, if anything at all?

    11. KHKristen Holmes47:05

        Yeah. I mean, I think what was so sad about that time period is- is y- you know, I think it was well-understood, you know? I- I think, um, a lot of those behaviors, I think to a degree are normalized, and I don't know that they're- the connection between depression... You know, she was s- no question, she had- she had massive seasonal affect disorder, which is one of the reasons why I'm so interested in, you know, um, kind of everything related to- to light and- and just the opportunity there for- for- for health, but, um, you know, she had major depressive disorder, and, you know, was not diagnosed pro- properly. I don't even remember- I have no idea if she ever even went to the doctor to, you know, to try to get treated. Um, so, you know, I- I- I think the- the biggest thing that I learned is that we can actually make choices. Um, and I- and I know that there are, you know, when you look at regions of the brain, we understand that people are predisposed, but I think there's a lot of things that we can- we can actually control to reduce our vulnerability to, um, to some of these diseases.

    12. SBSteven Bartlett48:18

        How has that experience defined and shaped you when you look back and connect dots?

    13. KHKristen Holmes48:24

        Yeah, I mean, I just, I always ... You know, I was very competitive, high-level ath- athlete representing (laughs) um, the US, and- and so there's definitely trying to understand my own body and my psychology so I could perform to my potential, but there's no question that, like, this whole ...... everything that, like, underpins the work that I do is, is trying to, to understand, you know, how we can improve our own situation so we can, um, you know, self-ac-actualize and, and live our potential. And, um, so that was... I always, you know, felt, um, so bad, you know, for my mom.

    14. SBSteven Bartlett49:10

        Why?

    15. KHKristen Holmes49:13

        You know, th- she wasn't able to become the version of herself, like, wasn't able to realize her potential, and she had so much. I can't believe you did this to me (laughs) .

    16. SBSteven Bartlett49:31

        Mm-hmm. Do you, would you like a tissue?

    17. KHKristen Holmes49:37

        Thanks. Oh (laughs) .

    18. SBSteven Bartlett49:43

        You're very, um, you're a very special person and it all makes, makes a ton of sense-

    19. KHKristen Holmes49:47

        (coughs)

    20. SBSteven Bartlett49:47

        ... why you've got such an incredible, incredible drive and mission to you. I didn't, I didn't know any of those, uh, what you just said, but they-

    21. KHKristen Holmes49:54

        I've never talked about that publicly, so I'm just... Yeah.

    22. SBSteven Bartlett49:58

        What a, what a wonderful way to have channeled such a unimaginable pain to then sort of fix, you know, hundreds of thousands of people's other lives and help them get closer towards their own potential.

    23. KHKristen Holmes50:13

        Yeah. I... And I, I never wanna, like, project my values onto other folks, but, but I think that's always been, like, at the core of, like, why I do what I, I do is, and the reason why I coached for so long is, I just love seeing people, like, realize their potential or understand their potential, knowing that we're always, of course, a work in progress. But I just, like, I want, like, everyone to be able to wake up and feel, you know, be energetic and, and be about to, like, really, really live the things that you, you care about, you know? And, and just, and understanding, I think, the path to that, you know, requires some work (laughs) , you know, in terms of making sure that you're attending to some of these non-negotiables that we're talking about. And I think sometimes it takes folks time to connect those dots and there's a lot of wonderful learning that comes with that, but I think if I can kind of help accelerate some of that wisdom and keep people from experiencing, I think, some of the pain that I felt, you know, it's worth it to me.

    24. SBSteven Bartlett51:24

        It's the most inc- credible, incredible thing that you've committed your life to because me and you are both aware that there's gonna be a ton of people who are either on a path towards such an addiction or are currently enthralled by such an addiction, and the work that you're doing, the message you're spreading is going to prevent and lift some of those people out of that situation, which has, has a wonderful karmic effect on the world. And I think if there's anything that we can convert our pain into, it is, it is exactly

15. 51:54 – 1:00:15

    What Alcohol Is REALLY Doing To Our Sleep

    1. SBSteven Bartlett51:54

       that. I wanna talk about alcohol.

    2. KHKristen Holmes51:56

       Mm-hmm.

    3. SBSteven Bartlett51:57

       I've recently quit drinking alcohol. I think it was about three to four months ago now. Um, it was so interesting, I had a conversation with some of my best friends of-

    4. KHKristen Holmes52:05

       Mm-hmm.

    5. SBSteven Bartlett52:05

       ... I said this on a podcast a couple of, couple of months ago. And one of my friends ha- was an alcoholic, so he managed to, um, quit alcohol and he's writing a book about it. And then as I look across the group of my other friends, none of them are alcoholics, but they're all sort of casual drinkers, and we were sat there together around this table having dinner, and he was telling us about this book he's writing about quitting alcohol, and I was sat there thinking, "That book that he's writing doesn't necessarily resonate with me because I've never had, I'd never felt like I've had an addiction or really, to be honest, any problem with it."

    6. KHKristen Holmes52:39

       Yeah.

    7. SBSteven Bartlett52:39

       I'm such, I was such a casual drinker, I would have maybe one glass of wine a week, if that. There's probably months I've gone without any alcohol at all. So I couldn't think of a reason to quit.

    8. KHKristen Holmes52:51

       Yeah.

    9. SBSteven Bartlett52:51

       So really I was saying to him, "Is there another book that someone else could write for me that just takes those people that are right, those casual drinkers-

    10. KHKristen Holmes52:59

        Mm-hmm.

    11. SBSteven Bartlett52:59

        ... that are right on the fence and just gives us a reason to nudge over the other side?" And because I have this podcast, I thought, "Do you know what? I'll just try and quit and see if, see what the implications-"

    12. KHKristen Holmes53:07

        Yeah.

    13. SBSteven Bartlett53:07

        "... are for my life." Alcohol, health, circadian rhythms. What do you, what's your perspective on all of this?

    14. KHKristen Holmes53:17

        Well, I, I, I like to think about it, I love this, the, the principle of non-neutrality, right? And, and this is how I like to think about behaviors and, and how I've kind of always thought about it is if you've got (laughs) a s- a series of behaviors, we talked a lot about, about sleep, um, and, and, you know, physiological things and you've got the psychological things, and they're either going to support your, your values, kind of who you wanna be in this world or they're not. And, and I think that's the lens with which I look at alcohol, you know? In what way is this supporting my values of growth and impact and, and presence and compassion and, um, tolerance? You know, the, the things that are, like, core to who I wanna be in this world. And, and I think when you look at it through that lens, a- the choices become really clear to me. Um, if you're honest with yourself and you have some degree of self-awareness, you understand what you care about, I think choices become a lot clearer. Like, there's way, way more clarity about how to live your life, um, in, in the micro, which is really what we're talking about, these just many choices throughout the day. Does it, does it, does it support who you want to be in the world or does it not? And, and there's very little gray actually. And the gray are excuses in, in my view. And, and we can rationalize and make stuff up-... you know, all day long, right, to, to, to make ourselves feel better. But when you can step back from all of that and look at it really, you know, taking yourself kind of out of the equation and look at it from a, a very objective standpoint, um, you know, I think a choice like alcohol becomes very clear.

    15. SBSteven Bartlett55:05

        But it helps me to socialize, Kristin.

    16. KHKristen Holmes55:09

        Yeah, if, if you need alcohol to bond or to, you know, form a connection, there's probably something else going on that is unaddressed in... from my perspective.

    17. SBSteven Bartlett55:23

        Is there such a thing as such a small dose of alcohol-

    18. KHKristen Holmes55:30

        Hmm.

    19. SBSteven Bartlett55:30

        ... that it doesn't matter, in your opinion?

    20. KHKristen Holmes55:34

        Yeah, I mean, I think it depends on who you are, um, and I th- I think there's a lot of individual variability there as, as well. I know resveratrol is, is something that's talked about a lot, and there's, uh, you know, uh, suppose there's... in wine and grapes, there's resveratrol, and that's been linked to, um, enhanced, uh, health and, and well-being. But I think you'd have to drink, like, 10 bottles or something to get the amount of resveratrol to actually make a... (laughs) um, uh, to, to make a dent. I don't think that's the argument, um, so yeah, I, I don't know that really any amount of alcohol is, is gonna be, is gonna be helpful. And we know from the literature that just one to two drinks per week, uh, will... can have, you know, negative implications, um, on, on health. So, um, it's actually... I, I don't know that any... like, even a moderate amount of alcohol is good for you.

    21. SBSteven Bartlett56:29

        What's the implications for our circadian rhythms that we've been talking about?

    22. KHKristen Holmes56:32

        Yeah, it's mainly because it impacts sleep. It's going to impact when you go to bed and when you wake up. Um, so I think that's the biggest, the biggest impact, and I think, again, when we go back to melatonin, um, you know, it's when you're disrupting that, that sleep onset/offset, um, that's going to, uh, obviously have all, all the downstream negative effects that we, we've already spoken about. So I suppose if we're drinking, remember, we're staying out later, so we're exposing ourselves to, to light. Um, so yeah, there's lots of... uh, we're gonna be eating later, uh, there's other, um, behaviors that accompany drinking that kind of l- you know, pile on the, the negative effects.

    23. SBSteven Bartlett57:14

        I was reading some research from the Sleep Foundation, and it says that a 2007 study with 29 young adults found that moderate doses of alcohol up to one hour before bedtime reduced melatonin production by nearly 20%. That's the study on alcohol and melatonin in young adults. A 2018 study of 4,908 Finnish participants found that sleep quality was re- was reduced by 9.3% after one glass of wine, and by 24% after two glasses of wine, and by almost 40%, 39.2%, after three or more glasses of wine or an equivalent amount of alcohol.

    24. KHKristen Holmes57:54

        Yeah.

    25. SBSteven Bartlett57:54

        Which is really, really staggering that your sleep quality will... could dip 40% after three glasses of wine.

    26. KHKristen Holmes58:01

        Oh, yeah. It's... I mean, we see... it is... we just finished this analysis actually looking at alcohol and markers of recovery, so heart rate variability and heart rate, and literally with every drink, it is just... there's a linear relationship in the decline. Like, and it is significant. Um, so I mean, yeah, it's... we're talking even one drink, um, will produce clinically significant reductions in heart rate and heart rate variability.

    27. SBSteven Bartlett58:27

        This was maybe the most compelling motivator for me to quit alcohol, was when I got my Whoop the first time, and then I think it was someone's birthday or something, so we went out, and I had a glass of wine or something. I woke, I woke up the next day, looked at my heart rate variability, which is the... a measure of how well I'm gonna be able to deal with stress and load and all those things the next day, how well my body's gonna be able to deal with life, and it was flashing red-

    28. KHKristen Holmes58:51

        Yeah.

    29. SBSteven Bartlett58:51

        ... which is like a warning. And it, and it says on there, when I clicked on the flashing red thing, it was like, "Did you have a really stressful day?"

    30. KHKristen Holmes58:57

        Mm-hmm.
16. 1:00:15 – 1:01:01

    The Effects Of Coffee On Our Sleep

    1. KHKristen Holmes1:00:15

    2. SBSteven Bartlett1:00:15

       Interesting. Super interesting.

    3. KHKristen Holmes1:00:17

       Yeah.

    4. SBSteven Bartlett1:00:17

       The other thing we obviously drink is coffee.

    5. KHKristen Holmes1:00:19

       Yes.

    6. SBSteven Bartlett1:00:20

       Caffeine. Surely there's a correlation between circadian disruption and caffeine.

    7. KHKristen Holmes1:00:23

       Yeah, so that's definitely one of the circadian... uh, kind of... it definitely can disrupt circadian rhythms if we're having caffeine, you know, within 8 to 12 hours, I would say, of when we intend to sleep. Um, it's gonna impact our sleep onset, of course. Um, and even if we're alr- you know, tired enough where we have, you know... we're sleep deprived, um, we...... might, might fall asleep, but it will invariably end up disrupting or fragmenting our sleep, so we're not kind of getting into that deeper stages of sleep, we're not achieving the sleep quality that, um, that is gonna le- you know, allow us to wake up feeling restored and refreshed. So, timing of caffeine is really

17. 1:01:01 – 1:03:37

    Shift Workers Have A Lower Life Expectancy

    1. KHKristen Holmes1:01:01

       important.

    2. SBSteven Bartlett1:01:02

       All of this conversation makes me have a huge amount of empathy for shift workers.

    3. KHKristen Holmes1:01:07

       Ugh.

    4. SBSteven Bartlett1:01:07

       And when I say shift workers, I don't, I don't mean people working, you know, in warehouses. I mean doctors, nurses, firefights- firefighters-

    5. KHKristen Holmes1:01:15

       Mm-hmm.

    6. SBSteven Bartlett1:01:16

       ... the police, um, truck drivers, people that are baking.

    7. KHKristen Holmes1:01:22

       Yeah, anyone who's up between the hours of, you know, for more than two hours between the hours of 10:00 PM and 4:00 AM is considered a shift worker. So it's, yes, it's a lot of, a lot of (laughs) individuals walking around who are shift workers. But people who are, you know, literally up during the biological night, um, you know, it's, it's a huge sacrifice. We know those folks, on average, are going to die 15 years sooner. It is, you know, shift work is considered a carcinogen by the World Health Organization. It's, you know, shift work is, um ... those folks make an enormous sacrifice.

    8. SBSteven Bartlett1:01:56

       They're gonna die 15 years sooner?

    9. KHKristen Holmes1:01:58

       On average.

    10. SBSteven Bartlett1:02:00

        I mean, that's terrifying.

    11. KHKristen Holmes1:02:02

        I know.

    12. SBSteven Bartlett1:02:05

        Is anybody, is anybody trying to s- solve for that?

    13. KHKristen Holmes1:02:08

        Yeah. I mean, that's a lot of the work that I do, (laughs) is, is looking at shift work, you know, and trying to understand, you know, what other levers, you know, can we deploy to offset some of the, the, the impact of, of being awake during the, the biological night, and, you know, time-restricted eating is a lever, you know, really thinking about when we're eating protein, um, you know, when we're viewing light, um, you know, what, what do the, what's the cadence of, of, of, you know, on/off, um, so we minimize the disruption to circadian rhythms. I mean, the, the fact is, like, the roster size at these hospitals are just simply not big enough to be able to, uh, I think, deploy schedules that mitigate some of the, the risk associated with this disrupted circadian rhythm. But it is frightening, and, um, you know, there is a lot of work to try to understand how we can mitigate some of the, the negative effects. But it's, it's, it's, it's a tough problem to solve.

    14. SBSteven Bartlett1:03:12

        It's not just, I guess it's not just that those individuals will die, you know, on average 15 years earlier, but their quality of life, I imagine, won't be as good, because if they're not sleeping-

    15. KHKristen Holmes1:03:22

        Yeah. I mean, mood-

    16. SBSteven Bartlett1:03:23

        ... consistently-

    17. KHKristen Holmes1:03:24

        ... depression-

    18. SBSteven Bartlett1:03:24

        Yeah.

    19. KHKristen Holmes1:03:24

        ... suicide. I mean, it's, it's, it's, it's higher, you know, for, for folks in, in these professions, you know, who are having to operate counter to the natural light-dark cycle.

18. 1:03:37 – 1:06:26

    Mental Health

    1. KHKristen Holmes1:03:37

    2. SBSteven Bartlett1:03:37

       So let's talk about that then. Mental health, depression, suicidality.

    3. KHKristen Holmes1:03:41

       Mm-hmm.

    4. SBSteven Bartlett1:03:42

       What's the correlation there between ...

    5. KHKristen Holmes1:03:43

       Yeah. So, there's a lot of interesting research. I mean, you know, one is just, f- d- you know, we talk about just the layperson, so getting outside of shift work, then we come back to shift work, you know, if you look at, um, this, most folks experience social jet lag, right, which is basically characterized as, um, you know, a, a big, a d- difference between our weekday sleep schedule and our weekend sk- sleep schedule, right? So pretty much anyone, (laughs) you know, between 20 and, 20 to 30, probably, is, you know, kind of falls into this bucket of, of having social jet lag. But one of the things that we, w- one of, r- a research study we saw looking at specifically a social jet lag in college students, they saw that for every hour of variability between weekday and weekend schedules, they saw a 17% increase in non-suicidal ideation. So, these folks aren't committing suicide, but they're fantasizing about committing suicide. And that increases 17%. And this was more pronounced in individuals who were already vulnerable. So kind of coming back to circadian disruption being present in 100% of mental health issues, we can see where shift workers would be extremely vulnerable, right, to mental health issues given that their variability, and we look at the WHOOP data, it's basically random in terms of looking at their sleep-wake time. It's so variable that it is, like, we can't even see a pattern. It's random, which is frightening.

    6. SBSteven Bartlett1:05:18

       Why is that frightening?

    7. KHKristen Holmes1:05:19

       Well, because, you know, the more variability you have, like, the more psychological and physiological, uh, you know, negative consequences there will be.

    8. SBSteven Bartlett1:05:32

       Is there a correlation here between how we deal with stressful events in our lives as well? Because I, I'm assuming-

    9. KHKristen Holmes1:05:38

       Yes.

    10. SBSteven Bartlett1:05:38

        ... there must be.

    11. KHKristen Holmes1:05:38

        Absolutely. Managing stress throughout the, the day, uh, and, and the degree, or, or even during the night, (laughs) um, can, uh, definitely increase your tolerance for stress. So, you know, deploying breathwork, for example, um, as, you know, on-demand self-regulation tool to pay down in-the-moment stress can be, and to activate the parasympathetic branch of the nervous system, can be really powerful. So, you know, I kind of call these mini moments of deactivation. So doing that proactively for folks who are in these high-steks- stakes, high-stress environments i- is an am- amazing strategy. Um, 'cause lots of those folks, again, if you think about just baseline when you are engaging in shift work and you're awake during the night, your

19. 1:06:26 – 1:07:54

    How To Reduce Stress In The Moment

    1. KHKristen Holmes1:06:26

       system is humming at a, uh, uh, a kind of a stress level that is above what would be normal, right? Like, your, your system is having to work so much harder to maintain homeostasis because you're doing exactly the opposite of what your body wants to do. So all of the kind of biological preferences are being, um, bypassed, right, when you're up during the, the biological night. So to pay down some of that stress-... you know, these many moments of deactivation are absolutely critical for that population. So that means, uh, just literally taking 30 seconds where you're doing the physiological sigh, for example, which we know has emerged as being the most efficacious breath work technique in the moment to reduce not only in-the-moment anxiety and stress, but actually, you know, your perception of anxiety and stress, like, in the future. (laughs)

    2. SBSteven Bartlett1:07:15

       What is that sign?

    3. KHKristen Holmes1:07:16

       Um, the physiological sigh, it's basically a double inhale followed by an extended exhale.

    4. SBSteven Bartlett1:07:22

       (inhales deeply) (exhales deeply)

    5. KHKristen Holmes1:07:23

       Perfect. That's exactly right. (inhales deeply) (exhales deeply) So basically, like, when you're crying, um, it- it- you know, you kind of do that double- double inhale followed by an e- extended exhale. But that, like, reduces stress in the moment in a really powerful way. And if you do that, you know, five, 10 times, um, you end up activating the parasympathetic branch, so you're reducing your heart rate. Um, and, uh, and- and, you know, kind of doing that throughout the day is- is a great way to, um, mitigate negative

20. 1:07:54 – 1:15:43

    Sleep Deprivation & How It Affects Our Actions

    1. KHKristen Holmes1:07:54

       stress accumulation.

    2. SBSteven Bartlett1:07:56

       There's a pretty unfortunate paradox, a pretty tragic paradox, in the fact that our shift workers, some of them, like doctors especially-

    3. KHKristen Holmes1:08:02

       Mm-hmm.

    4. SBSteven Bartlett1:08:03

       ... are the people that we need to be most focused.

    5. KHKristen Holmes1:08:06

       (laughs) Firing on all cylinders.

    6. SBSteven Bartlett1:08:07

       Exactly.

    7. KHKristen Holmes1:08:07

       Yeah.

    8. SBSteven Bartlett1:08:08

       But those are the people that are, f- from what I've learned today about the circadian rhythm, most likely to suffer with things like focus and sleep and all of those-

    9. KHKristen Holmes1:08:17

       Yeah.

    10. SBSteven Bartlett1:08:17

        ... things that are imperative to showing up well.

    11. KHKristen Holmes1:08:19

        Yeah. I mean, there's a relationship, you know, we, we know that with every 45 minutes of sleep deprivation accrued on the Whoop platform, we see a 5 to 10% next day decrease in mental control.

    12. SBSteven Bartlett1:08:31

        Mental control?

    13. KHKristen Holmes1:08:31

        Or executive function. So we- we measure this, um, with an MBAC and a Stroop, so these kind of, uh, performance tests to measure executive function, and we see for every 45 minutes of sleep debt accrued, we see up to 10% decrease or decline in next day executive function.

    14. SBSteven Bartlett1:08:51

        And what does executive function mean for people that are...

    15. KHKristen Holmes1:08:54

        Our ability to make decisions.

    16. SBSteven Bartlett1:08:56

        Okay. You used the word there sleep debt.

    17. KHKristen Holmes1:08:58

        Mm-hmm.

    18. SBSteven Bartlett1:08:59

        What is sleep debt?

    19. KHKristen Holmes1:09:00

        So that's basically what you need versus what you actually got, and that's highly individual, right? And- and that's one of the kind of beautiful things on the Whoop platform is that we learn your- your body, we learn how efficient sleeper you are, we learn what your optimal sleep-wake time should be, and we basically tell you how much time you need to spend in bed. So a lot of the work that my- my team has done specifically at Whoop is to try to understand, you know, what is this relationship to- of sleep debt to other performance metrics that we care about, right, that tell us a story about someone's ability to kind of function in their environment? And one of the studies that we did, um, was looking specifically at business executives, so CEO types, (laughs) um, and we- we basically looked at, um, it was a S- this one was a six-month study, um, looking at two different cohorts, uh, bo- you know, with, I think, equal distribution between men and- men and women. And- and what we saw was for every 45 minutes of sleep due- debt accrued in these business leaders, we saw a 5 to 10% decrease in next day executive function. So the leader's ability to make decisions in the presence of sleep debt, um, you know, gets- gets worse the more sleep debt you accrue. We did a follow-up study, and this one was wild. So we basically looked at, um, it was roughly, it was about 70, uh, business executives, CEO types, and we looked at, um, all of their objective markers, you know, sleep debt being one of them, and we look at the psychological safety of their direct reports during team meetings.

    20. SBSteven Bartlett1:10:39

        And define psychological safety for...

    21. KHKristen Holmes1:10:41

        Your- it- how, um, how safe you feel to show up in your environment as your true, most authentic self. And what we saw was, again, for every 45 minutes of sleep that the leader had, there was a significant decrease in psychological safety of the direct reports. So they felt less safe in their environment to show up as their true self when their leader had 45 minutes of sleep debt accrued. And- and some of these folks were carrying a couple hours of sleep debt, so... And there was a r- linear relationship between the amount of psychological safety and the amount of- of sleep debt the leader had. So, and what was so interesting and I think compelling about this research is that the leader had no idea, they couldn't perceive their own cognitive, physical, and emotional declines, right? But that's what's so insidious about sleep deprivation, is that you can't really tell when you're operating at a lower level. You just adapt to that lower level of functioning. But everyone around you can feel it, right, just with how you hold your f- hold your face, how you emote, um, the kind of eye contact you make, how tolerant you are. Um, and you- and you think about how sleep deprivation, you know, it- it, uh, and I think this is really what this research surfaces is just it's not just, sleep deprivation just doesn't impa- impact me, right? It's gonna impact every single person I come in contact with. And from a business perspective, just from a sheer, like, numbers perspective, Google, um, did a study called Aristotle, and they looked at cycle, they looked at a bunch of different metrics related to team performance, and what emerged in that study as being most predictive of team performance was the degree to which the team had psychological safety, felt safe in their environment to kind of show up as their- as their true self. And they brought in to the tune of $4.5 million more than teams who are lacking psychological safety. So this is, like, a really important concept that I don't think a lot of people talk about, but when we go back to this concept of the principle of non-neutrality, right, and what are behaviors that...... promote, enable you to live your values and, and sh- kind of show up as, as your, your best self as consistently as possible, minimizing sleep debt is right there at the top of the list.

    22. SBSteven Bartlett1:13:09

        It's fascinating. And, uh, as it relates to sort of accident and injury-

    23. KHKristen Holmes1:13:13

        Mm-hmm.

    24. SBSteven Bartlett1:13:13

        ... is there a correlation between-

    25. KHKristen Holmes1:13:14

        Yes.

    26. SBSteven Bartlett1:13:14

        ... sort of injury of one self and accidents you commit on others?

    27. KHKristen Holmes1:13:18

        Yeah.

    28. SBSteven Bartlett1:13:19

        Um, correlation between that and sleep debt?

    29. KHKristen Holmes1:13:20

        It's very well established that, um, the more sleep debt, uh, you're, you're carrying, you know, the more accident prone you are, um, you know, the, the, the, the, the more risk you're gonna take. Um, and, uh, yeah, and we see this in, in the medical field, we see this, um, you know, in, in, you know, just car accidents, and, yeah, it, the list goes on and on.

    30. SBSteven Bartlett1:13:42

        Car accidents. A 2016 study by the Foundation for Traffic Safety found that drivers who reported that they usually sleep four to five hours per day had 5.4 times the crash rate of drivers who usually sleep for seven hours or more a day, which is horrifying.
21. 1:15:43 – 1:19:00

    The Relationship Between Sex & Sleep

    1. KHKristen Holmes1:15:43

       super evident in all the research that we're doing.

    2. SBSteven Bartlett1:15:45

       What about sleep and sex?

    3. KHKristen Holmes1:15:47

       Mm.

    4. SBSteven Bartlett1:15:48

       In-

    5. KHKristen Holmes1:15:48

       Sex with a partner is a health promoting behavior, and we have found that in our re- (laughs) in our research. (laughs)

    6. SBSteven Bartlett1:15:54

       When, when, what, what research have you done?

    7. KHKristen Holmes1:15:56

       Yeah. And we just, we actually haven't published it yet so this is preliminary for- preliminary data, but, um, but we, w- people who, um, are reporting that they're having sex, uh, before bed, so within a, a few hours of, of when they intend to sleep, with a partner have, um, better markers of sleep and recovery.

    8. SBSteven Bartlett1:16:15

       You said with a partner very intentionally there.

    9. KHKristen Holmes1:16:17

       I did, yeah.

    10. SBSteven Bartlett1:16:18

        (laughs)

    11. KHKristen Holmes1:16:18

        We don't, we don't see the same effect, um, when folks are, are having sex without a partner and reporting it.

    12. SBSteven Bartlett1:16:24

        How do you have sex without a partner? (laughs)

    13. KHKristen Holmes1:16:26

        I mean, s- that, all right, I should say a partner like a spouse or a boyfriend or, you know, someone who you're consistently with, so-

    14. SBSteven Bartlett1:16:33

        Oh, okay.

    15. KHKristen Holmes1:16:33

        ... we're not, we're talking about, I guess, not one-night stands. Sorry, I should've clarified it.

    16. SBSteven Bartlett1:16:37

        I thought you meant with, like, without-

    17. KHKristen Holmes1:16:38

        Oh.

    18. SBSteven Bartlett1:16:38

        ... a human at all.

    19. KHKristen Holmes1:16:39

        Oh, got it. Yeah, we're ta- I'm talking about human sex here, yeah. (laughs)

    20. SBSteven Bartlett1:16:42

        Does masturbation-

    21. KHKristen Holmes1:16:43

        Sex with humans.

    22. SBSteven Bartlett1:16:43

        ... not have the same implications, do I-

    23. KHKristen Holmes1:16:45

        Um, we didn't, we didn't see big effects with masturbation.

    24. SBSteven Bartlett1:16:48

        (laughs) Are people reporting that, though, on Whoop?

    25. KHKristen Holmes1:16:50

        They sure are. (laughs)

    26. SBSteven Bartlett1:16:51

        They are?

    27. KHKristen Holmes1:16:51

        I should say that it is completely optional to track, so people can opt in to tracking these things. Again, it is completely de-identified. We have no ability to, uh, to know who's doing what in terms of journal tracking and behaviors, um, but, uh, yeah. So we don't actually see, uh, any big effects with, with masturbation and any markers of sleep and recovery, so no, no strong, no strong effects there.

    28. SBSteven Bartlett1:17:15

        We said something earlier about exercising before bed.

    29. KHKristen Holmes1:17:17

        Mm.

    30. SBSteven Bartlett1:17:18

        Now, if I have sex before bed and, you know-
22. 1:19:00 – 1:20:53

    Ads

    1. SBSteven Bartlett1:19:00

       As you know, this podcast is sponsored by Whoop, and people often ask me why I chose Whoop over all of the possible wearable options, and I've tried many of them, but Whoop for me stands out for several reasons. A, because of its non-invasive design-... B, because of its unique analytics, and C, a membership model that continually evolves with the product. But the biggest game-changer for me, which is reason D, is Whoop's ability to foster meaningful behavior change for me. With Whoop, I've been more attuned than ever before on how my daily activities can impact my sleep and stress levels. And their features, like the Whoop Coach feature, which they recently announced, and the journal and the weekly planner have been instrumental in helping me to maintain health and fitness habits that I previously struggled to achieve consistency with. If you're looking to improve your health and fitness this year, beyond January, then you've got to give Whoop a try. Go to join.whoop.com/ceo, and you'll be able to get Whoop for 30 days risk-free with zero commitment, and let me know how you get on. (page turns) Quick one. We are working with an exciting new sponsor on this podcast, Shopify. I'm sure you guys have heard of Shopify if you haven't been living under a rock. But for those that don't know, Shopify is a commerce platform revolutionizing millions of businesses worldwide. It is pretty incredible. They provide everything you need to start your business, and it's super simple to get started and to get your business out there. Here at The Diary of a CEO, we've used Shopify for a variety of our different product drops, the latest being the conversation cards, and without the help of Shopify, that wouldn't have been possible. It's mine and my team's go-to website for all things commerce-related. So, I'm giving you guys the chance to trial Shopify for $1. That's right, $1. Sign up for a $1 trial for a month by searching shopify.com/bartlett, all lowercase, keep it to yourself, and let me

23. 1:20:53 – 1:30:01

    What Is HRV & Why Is It So Important?

    1. SBSteven Bartlett1:20:53

       know how you get on. (page turns) The other thing I, I would love to talk to you about, because it's become a huge obsession in my life, is this word, guess it's not a word, it's an acronym, HRV, heart rate variability.

    2. KHKristen Holmes1:21:02

       Mm-hmm. Mm-hmm.

    3. SBSteven Bartlett1:21:03

       Been a- become absolutely obsessed with it.

    4. KHKristen Holmes1:21:05

       (laughs)

    5. SBSteven Bartlett1:21:05

       Maybe a little bit too obsessed with it, one might argue.

    6. KHKristen Holmes1:21:07

       Mm-hmm.

    7. SBSteven Bartlett1:21:07

       I just check it every day.

    8. KHKristen Holmes1:21:09

       Yeah.

    9. SBSteven Bartlett1:21:09

       So the first thing I do when I wake up in the morning is I look at it.

    10. KHKristen Holmes1:21:11

        Yeah.

    11. SBSteven Bartlett1:21:12

        Um, just to understand how my body ha- has recovered from the night before.

    12. KHKristen Holmes1:21:16

        Right.

    13. SBSteven Bartlett1:21:17

        Um, what is HRV?

    14. KHKristen Holmes1:21:19

        Mm-hmm. It's most simply the time interval between heartbeats, and, um, it's a function of the heart, but it, uh, originates in the autonomic nervous system.

    15. SBSteven Bartlett1:21:29

        Mm-hmm.

    16. KHKristen Holmes1:21:29

        And as we've talked about, the autonomic nervous system has two branches, the parasympathetic and the sympathetic. Parasympathetic is the rest and digest, sympathetic is, you know, fight or flight, and they're both competing to send signals to the heart. When you are super recovered, your, your heart is gonna be responsive to both branches of that autonomic nervous system in a very kind of, um, dynamic way. So whatever you wanna do and what's happening in your environment, you're able to basically make a match the more recovered you are (laughs) -

    17. SBSteven Bartlett1:22:01

        Mm-hmm.

    18. KHKristen Holmes1:22:01

        ... if that makes sense. So, um, you'll be able to respond and react to environmental stress in, in kind of a, a more high-performing way, I suppose, is the best way to say it. So, um, heart rate variability is, is kind of a measure of that ability to adapt to your environment in a functional way.

    19. SBSteven Bartlett1:22:21

        And a high heart rate variability, which is more varying beats, heartbeats-

    20. KHKristen Holmes1:22:26

        Mm-hmm, between-

    21. SBSteven Bartlett1:22:28

        ... are y- is, is better?

    22. KHKristen Holmes1:22:29

        Yeah, more variability, the better, so a higher heart rate variability should be correlated with, uh, uh, better adaptation to environmental stress.

Episode duration: 1:49:51