The Diary Of A CEO with Steven Bartlett - The Fitness Scientist: "Even A Little Alcohol Is Hurting Your Health!", "Late Night Screen Time Linked To Cancer!", "Working Shifts Kills You 15 Years Early!" - Kristen Holmes

Episode Date: January 4, 2024

If you enjoy hearing about the transformative power of sleep, I recommend you check out my conversation with Dr Matthew Walker, which you can find here: https://www.youtube.com/watch?v=Us8n8VBQn_c If you have ever wanted to understand what exactly Circadian Rhythm is, and its unbelievable total body impacts, this is the episode for you. Kristen Holmes is the Vice President of Performance Science at the health and fitness monitoring company, WHOOP. Kristen’s focus is on understanding the scientific, psychological and personal factors that either promote or harm human performance. In this interview, Steven and Kristen discuss everything from the amazing impact of harnessing your Circadian Rhythm, Heart Rate Variability, the psychology of peak performance, and how people can take control of their health. Follow Kristen: Instagram: https://bit.ly/47oC8fh Follow me: https://beacons.ai/diaryofaceo

Quick one. Just wanted to say a big thank you to three people very quickly. First people I want to say thank you to is all of you that listen to the show. Never in my wildest dreams is all I can say. Never in my wildest dreams did I think I'd start a podcast in my kitchen and that it would expand all over the world as it has done. And we've now opened our first studio in America, thanks to my very helpful team led by Jack on the production side of things. So thank you to Jack and the team for building out the new American studio. And thirdly to to Amazon Music, who when they heard that we were expanding to the United States, and I'd be recording a lot more over in the States, they put a massive billboard in Times Square for the show. So thank you so much, Amazon Music. Thank you to our team. And

thank you to all of you that listened to this show. Let's continue. What the research says is that people who are having sex within a few hours when they sleep have better markers of sleep and recovery. So does masturbation not have the same implications? Well, what was so interesting about this research is that Kristen Holmes is the vice president of performance science at Woo. 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. 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 p.m. and 4 a.m.,

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. You can have trouble having children. I mean, that's terrifying. We know that we haven't adapted to blue light. The light we get from screens. Yes. If you're viewing light during the hours of 10 p.m. and 4 a.m.,

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 a.m. because I'm a night owl. Total BS. You're making a choice. And if you want to perform consistently, increase your tolerance for stress,

and take control of your life, you need to... We want to eat. And need to, we want to eat. Most importantly, we need to... Kristen, why do you do the work that you do? I am irrationally passionate about human flourishing and the frameworks, policies, basically determinants of human flourishing. And I've kind of dedicated my life to understanding how the physiology and psychology work together to help people take control of their health so they can understand how to apply their energy and attention in a way that's truly rewarding.

What is your job title? I'm the Vice President of Performance Science, Principal Scientist at Whoop, which is a physiological monitoring technology company. And what does that mean? So I'm trying to make sure Whoop is a thought leader in human performance. So trying to see around the bend to understand what's going to be important for tomorrow in terms of

understanding how we can take control of the trajectory of our health. What are the markers that are important that we need to be tracking? 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, frontline healthcare clinicians, and military operators.

So kind of understanding some of these extreme professions and crafts and what the physiology and the psychology looks like, we can then kind of abstract and I think in some ways generalize what that means for the regular population who are experiencing less extreme demands on their time and their energy and their cognitive bandwidth. And you conduct your own studies? Yes. Yeah. So I'm a principal investigator on many studies, 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 and various aspects of expertise. But yeah, I mean, one of the studies that we published in May was looking at a thousand paratroopers in Army Alaska. So super extreme, you know, environments, you know, harsh, but the Army came to us. They were,

you know, if you understand, Alaska in general has a very high suicide rate. This base in Alaska has a lot of mental health issues, a lot of suicide, and they're trying to understand, you know, what is actually going on here. And 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 soldiers. And that one behavior was sleep-wake timing. So the more consistent and more stable was sleep-wake timing. So the more consistent and more stable the sleep-wake, the sleep onset and offset of these soldiers, the higher levels of positive psychological functioning. So workplace resilience, less homesickness, more feelings of control, more positive social networks. It bubbles up in every single piece of research that we do at Whoop. Sleep-wake timing, I think, is the mother of all performance optimization behaviors. Sleep-wake timing. So is this the same thing as your circadian

rhythm? 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. And your biological clock is kind of orchestrating these rhythms, right? Okay, so I'm going to have to pause and take this right back to monkey level stuff. Yeah. What is a circadian rhythm? As if you're explaining it to a 10 year old. Yeah. So it's basically physical, mental, and behavioral changes that happen over a 24 hour cycle. Okay. So here's my read on it and correct me if I'm wrong. There's a clock in my head. Yes. The suprachiasmatic nucleus is the master clock. Okay. Which is somewhere in my body. It's in the hypothalamus. So it's in my brain. And this clock regulates every cell in my body. Cell, tissue, organ. Okay. And it releases, it controls the release of a chemical, which makes those cells, organs,

every part of my body do stuff. Yeah. So it is your hypothalamus. So the suprachiasmatic nucleus, it responds to light and it responds to darkness. Okay. Okay. So that's the most pronounced entrainment cue for this master clock. And it then tells, it sends signals to every cell tissue in your body as to what it needs to be doing in the presence of light, in the presence of darkness. And when we are viewing light at a phase of the natural light-dark cycle, that is, if I am awake when I should be sleeping, or I am sleeping when I should be awake, when my body anticipates that, it causes huge amounts of stress in the system. If we do this once or twice, not a big deal. But if we're doing this chronically, okay, it has massive health consequences, you know, cancer, metabolic disease, you know, cardiovascular

disease, a hundred percent of mental health issues, there will be some level of circadian disruption. Okay. So when this light information comes in and tells these clocks what to do, if I am going outside of my natural biological preferences, that is circadian disruption. And if you think about how many folks are walking around with circadian disruption, it is mind-blowing. I mean, basically the kind of the definition that's been thrown out there is if you are awake from the hours of 10 p.m. to 4 a.m., if you're awake for two hours between 10 p.m. and 4 a.m. for two days per week for 25 days of the year, you qualify as a kind of card carrying shift worker and you likely have significant circadian disruption. Which means that I have... You are at risk for some of the... And it's not going to happen tomorrow, but if you continue on that pattern that I just described, you are putting yourself at increased risk for cancer and cardiovascular

disease, metabolic dysfunction. You can have trouble having children. It impacts fertility, mental health, psychiatric disorders. There is a disease or disorder that circadian disruption doesn't touch. So a way of thinking about this, so that I and everyone else can understand is there's this master clock in our hypothalamus, look at me, hypothalamus, and this master clock regulates all of the other clocks throughout our entire body. And there's millions of them, right? Basically. Yes. And the thing that's the master clock is using as a signal, the clock in our brain is light and darkness. That's its most reliable. That's the most strongest. Yes. That's the signal it cares about, it listens to

the most, but there's other signals as well. And if that master clock, so if I'm up at 4am and I'm looking at a light at 4am, that master clock is going to start firing off chemicals to all the other clocks. And then all the clocks are going to be out of sync because then when I wake up, it's light. You're confusing your system. I'm confusing my body and it's firing off in all kinds of different ways. So I need to form an alignment, which means basically sleeping at the right time, exposing myself to darkness at the right time, et cetera, et cetera. Your body loves regularity. And the problem is Moderna is not set up for that. You know, we have access.

You know, I think all the circadian research, unfortunately, was done after the advent of electricity. So we're kind of fighting, you know, we're starting to see the, I think, deleterious effects or 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. Blue light being the light we get from screens. Yes. There was a study that looked at the timing of light and its impact on mood and brain 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 p.m. and 4 a.m., it actually has a pro-depressive effect. So it impacts your dopamine system, reward, motivation, right? So when we wonder, you know,

oh, what is this mental health crisis? I mean, we have to look at light first. And I just don't know. And I think what's hard about the discussion and hard about this behavior is that, you know, it's really hard for people to not engage with their phones, you know, before bed. It has its own addictive properties, right? But we just have to understand that these, our relationship to light will directly influence the trajectory of our health. There's just no question about that. To understand this from a more sort of prehistoric ancestral lens, if we go back, I know, tens of thousands of years to how maybe some of our ancestors used to live, they would have food at certain times and they would have light exposure at certain times. They

didn't have artificial light and invented that yet. The modern world is very much the antithesis of that. We have food whenever we want it. I can order a cookie at 3am if I want to eat a cookie at 3am and I can watch a YouTube video that I ever see, for example, like and subscribe at any hour of the day. So is this kind of like a misalignment issue with the way our body was designed by nature and the world we now live in. Yeah, we have not evolved to digest food in the middle of the night or to view light in the middle of the night or to be super active in the middle of the night. We just haven't. And it does, 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 really interesting to, I think, see some of their behaviors, some of their sleep-wake behaviors. And this is fascinating. There is a study done looking at

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, because I think that's, you know, I think that's the reason a lot of people are like, oh, I have to go to bed at 1am because I'm a night owl. No, you're making a choice, generally speaking. Now, you're making a choice,

generally speaking. Now, this is in healthy populations, not people who have circadian disorders and things like that. Generally speaking, 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 think that just those two examples are really compelling in that, you know, we have evolved to kind of wake up and fall asleep in relation to this light dark cycle. So all of this stuff we say to ourselves, because I say that to myself all the time, I've told myself I'm a night owl and I've given myself the whole chronotype

spiel. That's BS. Yeah. In my opinion, the way I interpret the literature, it seems that the variability that I think is talked about or how we think about it as a society in terms of there's chronotypes that are very, you fall asleep, you're genetically predisposed to fall asleep at 1 a.m. and I'm genetically predisposed to fall asleep at 9 p.m. Yeah, 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, it's age-related as well. But for the most part, I don't think this variability is as pronounced as what we say it is. Sleep. Yeah.

So conventional wisdom says it's all about how many hours you spend sleeping. This has already been shown to be not true. Sleep duration is important, right? We can put a pin in that. But sleep regularity predicts all-cause mortality. And this is just recently published, actually, not by my team. But looking at, it was actually UK Biobank, 60,000 people, 10 million sleeps, objective measure of sleep. And they found that sleep regularity predicted mortality and independent of sleep duration. So 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. What did they find? What was the conclusion of that? Was there a sort of a percentage variance in those that had irregular and regular sleep?

Yeah, so the sleep onset offset times, 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're 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 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. To stress the next day. To stress the next day. So life load. So sleep-wake time is really important. And we're doing research across every age bucket. But you can imagine that if these are the most robust humans on the planet, and they have 70 minutes of variability that is tolerable. Within that population, some are a little bit sooner in terms of the, or can deal with less variability and others can deal with slightly more variability,

but the mean is 70 minutes. So you can imagine for individuals who are more vulnerable, who are less robust physically, mentally, emotionally, their tolerable level is going to be a much narrower. 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? What's actually going on from like a chemical physiological perspective? Yeah. So one of the things that's suppressed is melatonin. And 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 melatonin, that is gonna impact us on every level and make us more vulnerable to disease and disorders. So that is probably one of the most important thing when we have super unstable sleep-wake time, we are going to have suppressed melatonin production, which leads to inflammation in the body. It's melatonin, I think, is one of the big players in the story. Growth hormones. Yes, yes. And typically, if you're not going to sleep, if you're going to sleep late, you will not release a human growth hormone as you'll get less of a bolus of release. And why does that matter? That's when all the physical restoration happens. So all the

regeneration physically. So for bypassing that, we're basically all the work that we did in the gym or, you know, everything that we did during the day, we're just not going to recover from that in the same way that we would if we were getting that sleep. Is growth hormone essentially the thing that causes our sort of muscles to grow and repair? Yeah. Essentially. So yeah, I sometimes think this because 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.

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 versus going to the gym, because my brain now goes, well, you're not going to get the recovery and sort of restoration anyway. The benefits. Yeah, the benefits of going to the gym if you're poorly slept that night. Yep. I think if you're consistently getting decent sleep and consistently

going to bed and wake up some more times, I would say it's okay to prioritize exercise sometimes, but sleep is very important and is probably the thing that needs to be prioritized first. How consistent are you with your sleep? Very consistent. I heard that in 2017, you started trying to sleep within sort of 25 to 30 minutes every single day, the same sleeping window. That's right. Yeah, And yeah, it was a

paper that came out by Andrew Phillips actually in the summer of 2017. And it basically was a four-year study that was conducted at Harvard University looking at students and they were basically students sleep and they're trying to see, okay, you know, what aspect of sleep is predictive of things like GPA and other, you know, measures of kind of flourishing. And what they found is that basically sleep-wake time predicted GPA. What's GPA for people? 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 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, you know, NBA, NFL, MLB, you name it. Like the biggest high performers like in the world. And I started tracking this, you know, just manually at the time at Whoop, we didn't actually track this. This wasn't automated. I had to like, you know, kind of do this in Excel. And then sure enough, you know, sleep, wake time started predicting all of these performance metrics that people care about. And we started rolling in some subjective measures. We had internal load, we had external load, of course. So all of those objective measures, but I started rolling in some subjective measures. We had internal load, we had external load, of course. So all of those objective measures,

but I started rolling in some subjective measures and sure enough, sleep-wake time just continued to ladder up to all these performance variables that people care about. So I started, of course, because I have access to all of these data, I started, I'm like, shit, 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 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, I literally have not been sick. And, you know, I do a lot of other things well, but that has been the single biggest change. Just sleeping and waking up at the same time. That's it.

What is your routine there? How do you ensure that happens? Because... Yeah, so the key to that is stabilizing when I wake up. So even when I travel, and I do travel, and I travel internationally, I travel to the West Coast, I try to maintain my home time zone as much as I can, as long as I can fulfill my business commitments. And there might be a social element as well. But for the most part, 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 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 that we can talk about. Sleep debt is wild in some of its correlations like psychological safety and executive function. But yeah, so I kind of, that's how I manage short sleep. But 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. And what time do you wake up and go to sleep?

So I go to bed around, I kind of get into bed usually around 9.15, 9.30. I read for a half an hour, 45 minutes, a book, printed page, dim light. And then I fall asleep usually around 10. And then I wake up like at 6, 14. No, I'm just kidding. Like around six, around six. You know, whenever I talk about these subjects, the rebuttal I get is one you might be able to predict. It's from a group of people that I can't yet relate to. Do you know who I'm talking about? Parents. Oh yeah. Yeah. Well, shit. I've had two kids, so I totally understand the whole parenting thing. So yeah. I mean, there's no question there are going to be times in your life where you're literally a shift worker because you're caring for a sick parent or a sick child, or you just

literally have kids and they're young. You're a shift worker. I mean, there are things you're making decisions to go out and socialize in times that maybe aren't optimal for kind of human functioning. But yes, there's no question that there are periods in your life where it's going to be harder. That said, there are some things that you can do to mitigate some of the negative effects of both duration and timing. And one of those things is dialing in your feeding window, which is another kind of circadian behavior. So the timing of when you eat is pretty important and can at least check some of the boxes in terms of its impact on metabolic functioning and heart health and things like that. So let's talk about that then, meal timing. What do I need to know about when I

should be eating, what I should be eating, and the implications that has on my circadian rhythm, my body clocks? Yeah. So it's in the literature, there's time-restricted eating and there's time-restricted feeding. And time-restricted feeding generally, if you're reading the literature, is going to refer to mouse models. Time-restricted eating will refer to human studies. Mouse models being studies they did with mice. Yeah, sorry. Yeah, mice studies done with mice are just time-restricted feeding. 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. 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 component to it. It's more about the timing. And there's been a lot of interesting studies that have been done that show if you eat within kind of eight to 12 hour window, you will have much better metabolic outcomes. And this is pretty, this is well-established. And if we see in the WHOOP data that if you're, if you stop eating three hours prior to when you sleep, to when you fall asleep, markers of sleep and recovery are exponentially better. So timing of meals really does matter. And there's no question

that, and we know this from other research, you're more primed to metabolize food closer to when you wake up in the morning. So earlier in the day, you're going to be much more primed to utilize the nutrients that you've digested. So does that mean we should be eating, we should have sort of an earlier eating window? Yes. Yes. You know, Brian Johnson. Of course. Yeah. I know he stops eating at 11am. Which is crazy. 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 would go so far to say that regardless of what it is you're eating, because a lot of folks cannot afford to eat

high quality food. That's just a reality. And a lot of those folks do suffer from higher rates of cardiometabolic dysfunction. But if we can just consolidate our eating window to eight to 10 hours, we get ourselves like 60% of the way to our kind of metabolic goals. Again, it's not to say that content and quality does not matter. It absolutely does. But 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 an eight to 12 hour window, we will improve our health.

And what's your eating window? So I do about 10 hours. Okay. Yeah. So I definitely, I pretty much don't eat after the sun goes down. When you say the sun goes down? Sunsets, yeah.

Is that like 5 p.m.? I mean, now it's early, yeah. So I give myself like an hour window. Yeah, like right now it's definitely early. But for the most part, I can kind of get away with it based on my lifestyle. So ideally between sort of 7 a.m. and 4 p.m. And then just make sure you're not eating, you know, two to three

hours before you fall asleep. Yes. That's the big key, I think, is you want a nice big buffer between yeah, when you have your last calorie and when you go to sleep. Because that, they're both, so digestion is a parasympathetic activity. What does that mean? So that means, so your autonomic nervous system has two branches, you're parasympathetic and you're sympathetic. You're parasympathetic is your rest and digest, right? We also want to be in a parasympathetic state

when we're sleeping. So when we are digesting food, we're basically kind of confusing our system in terms of where it should apply its resources, right? So it basically diverts resources away from, you know, the sleep and the restoration. And that's where, you know, if you have a big meal, you'll notice your heart rate is really, is a lot higher, right? And your stress score is higher, right? Some of the features on the Whoop app. And when you are not having to digest, you'll see your stress score is lower. You'll see

your heart rate is lower. Your heart rate variability would be higher in those situations. We want to make sure that when we're sleeping, we are not diverting any resources away from sleep. I mean, alcohol is another one, right? Like you just to metabolize alcohol, you're diverting significant resources

away from the regeneration and the recovery that needs to happen during sleep by bouncing you out of deeper stages of sleep. So the same sort of effect happens with food. And we see this at population levels on the Whoop app. It's just very apparent that meal timing and alcohol are really the two biggest disruptors to a good night's sleep. So interesting, because I've always wondered,

there was a time in my life where I routinely ate super late at night, because I would work very, very hard during the day. I would basically forget to eat. I'd get home at maybe nine or 10 at night. I would then order the food at nine or 10, which means it comes at 11 or 12. And then I'd eat at 11 or 12. Yeah. It's very stressful for your system. Yeah. Tell me about it. The interesting thing that I started to notice was when I did that, I woke up feeling like I hadn't slept.

Yeah. And I've always wondered why. So I arrived at the same sort of self-constructed conclusion that if I put food into my body at midnight, it basically keeps my body on for a couple of hours. Yeah, that's exactly right. That's a perfect way to describe it. I would see exactly that in the WHOOP data, which is, I would see that my heart rate went up to about 70 beats per minute for the first three hours. It was almost like my body was

still walking around or something. And then three or four hours in, it would start to fall again back to, I don't know, 45, 50. After you've metabolized the food. Yeah. And we know, there's a really nice study that looked at basically everyone is eating the exact same meals and they're relatively the same age. There's a really beautiful design. And they basically looked at folks who are eating after 3 p.m. and folks who are eating before 3 p.m. And the folks who ate a bulk of their calories before 3 p.m. had significantly better metabolic outcomes and lost more weight. So again, there's no calorie restriction component here.

You know, they're all kind of eating similar diet, similar macronutrient distribution, similar calorie content. And it's the folks who were eating a bulk of their calories prior to 3pm who had the best outcomes. Exercise. One of the issues that I have sometimes in my life, today's one of those days where because I was up very early this morning, it meant that I didn't go to the gym this morning, which means I'm probably going to get home after being in the studio, being in the office today at maybe 7, 8 p.m. And I'm super

hungry then usually, right? And I also need to work out. So sometimes what happens is I choose to work out first and then obviously 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 at like 11 or 12 p.m. at night. And there was this old train of thought that that was a good thing to do because people would say, oh, you're going to be tired when you get in bed. But that doesn't seem to be what happens.

Yeah. Do you feel more energized? I feel more energized. 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 kind of flowing through the system and it takes time for them to go back to normal levels. So to kind of get back to homeostasis is going to take some time. And so, yeah, I mean, it would make sense that you're kind of activated 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 light, which is going to make you feel like more activated. And it's again, telling your body that it's time to be awake and alert. 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. My partner always gets up in the morning, walks out into the balcony and sits out there for 10 or 20 minutes in the morning. Oh my gosh, I love that. Yes, I love to hear that. Yeah, she's the best. It's so annoying. She gets everything right. Oh, I love it. Yeah. But, but for sure that you want to get light within, you know, 100,000 lux is, is pretty much what you want to get within, you know, five to 20 minutes of waking up to tell your body, like it's time to go. 100,000 what? Oh, lux. So just like photon energy. So pretty much if you're outside for five to 20 minutes, 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. Can't you just go look into a lamp or something? It will just take longer because it doesn't have the same light intensity. But if you're waking up prior to when the sun gets up, yeah, turn all the lights. You want to try to mimic day as much as possible. And then once the sun does come up, it's good to get outside. And before you get in bed,

you referenced that you read books versus being on an iPad or screens, et cetera. Does the same philosophy and principle apply to light exposure before sleep as to food exposure before sleep? Oh, no question. Absolutely. We want to try to restrict light.

Basically, after the sun goes down, we want to dim our home environment to the degree that we can. We want to try to minimize all artificial light in the lead up to bed. All artificial light? Yes. Yeah. You want to make it as 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. But again, like we don't, we want to protect our melatonin release, right? And for all the reasons I kind of have explained.

When we don't have it is linked to every disease and disorder, right? So we know this. So we want to protect our melatonin release. And the only way we can release melatonin is by darkness. We need to be exposed to darkness in order for that master clock in our brain to know that it's time to go to sleep. And again, be able to tell our body, our tissues and organs and cells and our inner body what it needs to do at that moment. When I was at the Whoop headquarters in Boston, not so long ago, I saw them working on sleep masks. And I think I've always been quite dubious about sleep masks.

You know, you get on those planes and they hand you a sleep mask in the little bag. I always thought, what a bunch of weirdos, you know, like putting that, strapping that thing to your face. Yeah. How embarrassing. I'm one of those weirdos now. Yeah. I mean, it's hard, even the little dot on your, you know, from your alarm clock or your TV is going to emit enough light. We're so sensitive to light, artificial light. So natural light, like the moon, totally fine. But any other type of light is really going to impair our ability to get into these deeper stages of sleep where all the restoration and regeneration happens.

Do you use a sleep mask? I do. Yes. What's your sort of routine there? Yeah, just when I start to feel sleepy, I just put it on and go to bed. Do you listen to anything when you go to sleep? No, I don't. Are you aware of any research that might indicate that listening to serial killer documentaries at 3 a.m.?

I think in principle, anything that activates you, stimulates you cognitively or makes you energized, you probably want to avoid reading. Yeah. Interesting. I think there's a group of us out there. I'm yet to meet them, but I know that I'm not alone. I like to listen to horror and thriller and serial killer stuff at, you know, very late at night. And it helps us to sleep, or at least that's what we tell ourselves. I think if you perceive it as helpful,

it probably is, you know, and I think that's where, and if your objective data shows that you're getting, you know, the requisite time in these deeper stages of sleep, then go with it. I think, I think what is actually, there's definitely the cold, dark, quiet, right? You need your room to be cold. You need to be dark. You need to be quiet. So there's the environmental stuff.

You need to stop eating a few hours before bed, ideally. You need to have stable sleep, big time, ideally. These are all things that are gonna drive getting into these deeper stages of sleep. But the other thing that you probably do really well is you manage stress throughout the day. You know, like you, I think that's another, like the things that we do during the day, how we, you know, whether or not we're living our values, right? Do our behaviors align with things that we care about? Are we thinking about the things that we want to be thinking about? Are we managing our relationships effectively? So all the things that can manifest as stress, negative stress, will invariably rear its head

during our sleep. But if we're managing those things during the day proactively and relatively well, generally speaking, sleep should happen pretty naturally. There's a huge group of people who listen to podcasts like this. And as they listen to these podcasts, they just feel more depressed about their situation. You know, because 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, 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? They know deep inside, much of it is a lack of discipline.

They know they could not watch YouTube. They know they could put their phone away at 9pm. They know they could not eat the cookie super late at night. They know they could not watch YouTube. They know they could put their phone away at 9pm. They know they could not eat the cookie super late at night. They know they could, 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. 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, body clock loving side? 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, 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, they don't really know who they want to be in the world. And they don't maybe understand exactly what it is that they value. They're fuzzy about their desires, about their values.

And I think you end up, when you're fuzzy about your desires and things that you value, you end up flinging yourself in all sorts of directions, emotionally, physically, mentally, right? 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, you know, who don't support those values. And I think we're way too lenient on our circle of friends. And in the sense of, you know, I think we keep people around in our life who don't necessarily help us become a better version of ourselves. Have you had to shed some people? Yes, absolutely.

Why did you shed them? Because it didn't really support who I wanted to be. Who did you want to be? I wanted to be able to wake up at a very simple level with as much joy and energy as I could. And I wanted to be present for my kids. And so I think folks are engaging in behaviors that, that I think, you know, create a situation where, yeah, I don't know how to say this without like- Just say it. Yeah, I mean, I think, you know, for me, you know, I grew up in a household where,

you know, my mom was an alcoholic. It was a tough environment. And, you know, she ended up, you know, dying of cirrhosis and, you know, it's not easy, you know, so being in that kind of environment. So I think for me, you know, you end up, it's crazy how when you live that life, you end up repeating those patterns. And I think, you know, I had to, you know, even though for me personally, I made choices where, you know, I really never drank alcohol, right? Because I saw how it destroyed my family. But yet I was still hanging around people who were engaging these behaviors and, and it just was impacting me at my core. And it didn't mean that I didn't love those folks, that was just like the norm. Like it is just wild to me how educational institutions normalize binge drinking at a level that is just so destructive. And, you know, and just to be, I suppose to just be around that all the time, like

was just really not allowing me to show up daily as the person that I wanted to just be around that all the time, like was just really not allowing me to show up daily as the person that I wanted to be, even though I wasn't engaging in that behavior. Like it's still like, it just, yeah, it just made me feel like I couldn't be the version of myself that I wanted to be. So yeah, just a lot of hard decisions, you know, but I let go of a lot, you know, to be able to create an environment and infrastructure that supported who I wanted to be in this world. 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's a completely different conversation. What is it like growing up with a mother who

you observe at a very young age? You were how old? I'm in my whole life. Your whole life? Yeah. As a child, when you see a parent, someone you love, that is sort of gripped by addiction, what is that like? Yeah, I mean, I think at a fundamental level, you just feel deprioritized, I think, generally. You know, like you, you know, I think you feel, you know, you're unsupervised, number one.

There isn't a lot of supervision, you know, so you end up like really having to fend for yourself. My dad worked a lot. You know, he was definitely a workaholic, such a good man, so much integrity. But I think that was his form of escape. But it kind of leads, you know, you got to figure out how to eat. You know, you got to 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's hard to form emotional attachments, I think, as an adult, unless you really work through that, because you're afraid that you're

not going to be taken care of. What did you come to understand about your mother's addiction and what she was struggling with, if anything at all? Yeah. I mean, I think what was so sad about that time period is, you know, I think it was well understood. You know, I think a lot of those behaviors, I think to a degree are normalized.

And I don't know that the connection between depression, you know, she was, it's no question. She had massive seasonal effect disorder, which is one of the reasons why I'm so interested in, you know, kind of everything related to light and just the opportunity there for health. But, you know, she had major depressive disorder and, you know, was not diagnosed 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. So, you know, I think the biggest thing that I learned is that we can actually make choices. 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 actually control to reduce our vulnerability to some of these diseases. How has that experience defined and shaped you when you look back and connect dots? Yeah, I mean, I just, I always, you know, I was very competitive, high level athlete representing the US.

And so there's definitely trying to understand my own body and my psychology so I could perform my potential. But there's no question that like this whole, everything that like underpins the work that I do is trying to understand, you know, how we can improve our own situation so we can, you know, self-actualize and live our potential. And so that was, I always, you know, felt so bad, you so bad for my mom.

Why? You know, she wasn't able to become the version of herself. Like, wasn't able to relapse her potential. And she had so much. I can't believe you did this to me. Would you like a tissue? Thanks. You're a very special person and it all makes makes sense why you've got such an

incredible incredible drive and mission to you i didn't i didn't know any of those what you just said but i've never talked about that publicly so i'm just yeah what a what a wonderful way to have channeled such an 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. Yeah. I never want to like project my values onto other folks, but I think that's always been like

at the core of like why I do what 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 be able to like really, really live the things that you care about, you know, and just in understanding, I think the path to that, you know, requires some work, 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. It's the most incredible, incredible thing that you've committed your life to because me and you are both aware that there's going to 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 that. I want to talk about alcohol. I've recently quit drinking alcohol.

I think it was about three to four months ago now. It was so interesting. I had a conversation with some of my best friends. I said this on a podcast a couple of months ago. And one of my friends was an alcoholic. So he managed to 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've never felt like I've had an addiction or really, to be honest, any problem with it. 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. 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 those casual drinkers 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, you know, I'll just try and quit and see what the implications are for my life.

Alcohol, health, circadian rhythms. What's your perspective on all of this? Well, I like to think about it. I love this, the principle of non-neutrality, right? And this is how I like to think about behaviors and how I've kind of always thought about it is if you've got a series of behaviors, we talked a lot about sleep and physiological things, and you've got the psychological things, and they're either going to support your values, kind of who you want to be in this world, or they're not. 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 presence and compassion and tolerance, you know, the things that are like core to who I want to be in this world. And I think when you look at it through that lens, the choices become really clear to me. If you're honest with yourself and you have some degree of self-awareness, 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 in the micro, which is really what we're talking about. There's just many choices throughout the day. Does it support who you want to be in the world or does it not? And there's very little gray,

actually. And the gray are excuses in my view. And we can rationalize and make stuff up, you know, all day long, right? 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 very objective standpoint, you know, I think a choice like alcohol becomes very clear. But it helps me to socialize, Kristen. Yeah, if you need alcohol to bond or to, you know, form a connection, there's probably something else going on that is unaddressed from my perspective. Is there such a thing as such a small dose of alcohol that it doesn't matter, in your opinion?

Yeah, I mean, I think it depends on who you are. And I think there's a lot of individual variability there as well. I know resveratrol is something that's talked about a lot. And there's, you know, I suppose there's in wine and grapes, there's resveratrol. And that's been linked to enhanced health 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 dent. I don't think that's the argument. So, yeah, I don't know that really any amount of alcohol is going to be helpful.

And we know from the literature that just one to two drinks per week can have negative implications on health. So it's actually, I don't know that any, like even a moderate amount of alcohol is good for you. What's the implications for our circadian rhythms that we've been talking about? Yeah, it's mainly because it impacts sleep. It's going to impact when you go to bed and when you wake up. So I think that's the biggest impact.

And I think, again, when we go back to melatonin, when you're disrupting that sleep onset offset, that's going to obviously have all the downstream negative effects that we've already spoken about. So I suppose if we're drinking, we're staying out later, so we're exposing ourselves to light. So yeah, there's lots of eating later. There's other behaviors that accompany drinking that kind of pile on the negative effects. 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 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. Yeah. Which is really, really staggering that your sleep quality could dip 40% after three glasses of wine.

Oh, yeah. 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. So, I mean, yeah, it's, we're talking even one drink will produce clinically significant reductions in heart rate and heart rate variability. 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 up the next day, looked at my heart rate variability, which is the measure of how well I'm going to be able to deal with stress and load and all those things the next day, how well my body's going to be able to deal with life. And it was flashing red, which is like a warning. And it says on there, when I clicked on the flashing red thing, it was like, did you have a really stressful day? Are you sick? Or did you drink alcohol last night? And I felt so targeted. I know. I was like, how does this thing know

that I had one glass of wine last night with my friends? Why is something flashing red inside of me? People keep diaries on Weep, don't they? They keep like the Weep journal. They do, yeah. It's a goldmine of information, actually. Really? Yeah.

What have you learned from that in terms of alcohol? I imagine that's where a lot of the conclusions come from. Yeah, I mean, we see a 6% reduction in next day recovery after alcohol on average. So this is, you know, one drink to 10 drinks, you know, it's just basically looking at the average is 6%. Okay, so the average of, okay. Recovery. So if someone was binge drinking, they could have a 30 or 40% reduction.

Yeah, but it kind of, and we might, and that specific data point, we might have controlled for the 30 drinks. It's probably somewhere in the range of five drinks per night. And the average recovery reduction is 6%. And that's relying on self-reporting, right? So I wonder if there's biases. There might be, yeah.

People that had 10 drinks think they had four. Yeah, exactly. I don't really remember how many drinks I had. So yeah, I don't remember how many drinks I had. Interesting, super interesting. The other thing we obviously drink is coffee. Yes. Caffeine.

Surely there's a correlation between circadian disruption. Yeah, so that's definitely one of the circadian, it definitely can disrupt circadian rhythms if we're having caffeine within 8 to 12 hours, I would say, of when we intend to sleep. It's going to impact our sleep onset, of course. And even if we're tired enough where we're sleep deprived, we 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 is going to allow us to wake up feeling restored and refreshed so timing of caffeine is really important all of this conversation makes me have a huge amount of empathy for shift workers. And when I say shift workers, I don't mean people working in warehouses. I mean, doctors, nurses, firefighters, the police, truck drivers, people that are baking.

Yeah. Anyone who's up between the hours of, you know, for more than two hours, between the hours of 10 p.m. and 4 a.m. is considered a shift worker. So it's, yes, there's a lot of individuals walking around who are shift workers. But people who are, you know, literally up during the biological night,

you know, it's a huge sacrifice. We know those folks, on average, are going to die 15 years sooner. It is, you know, 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, those folks make an enormous sacrifice. They're going to die 15 years sooner?

On average. I mean, that's terrifying. I know. I know. Is anybody trying to solve for that? Yeah. I mean, that's a lot of the work that I do 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 being awake during the biological night and, you know, time-restrict the biological night. And, you know,

time-restricted eating is a lever, you know, really thinking about when we're eating protein, you know, when we're viewing lights, you know, what's the cadence of, you know, on, off. So we minimize the disruption to circadian rhythms. I mean, the fact is like the roster size at these hospitals are just simply not big enough to be able to, I think, deploy schedules that mitigate some of the risk associated with this disrupted circadian rhythm. But it is frightening. And, you know, there is a lot of work to try to understand how we can mitigate some of the negative effects, but it's a tough problem to solve. 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 consistently. Yeah. I mean, mood, depression, suicide. I imagine, won't be as good because if they're not sleeping consistently. Yeah, I mean, mood, depression, suicide. I mean, it's higher, you know, for folks in these professions, you know, who are having to operate counter to the naturally dark cycle. So let's talk about that then. Mental health, depression, suicidality.

What's the correlation there between? Yeah. So there's a lot of interesting research. I mean, you know, one is just, you know, we talk about just the lay person. So getting outside of shift work, we come back to shift work. You know, if you look at this, most folks experience social jet lag, right? Which is basically characterized as, you know, a big difference between our weekday sleep schedule and our weekend's sleep schedule, right? So pretty much anyone, you know, between 20 to 30 probably is, you know, kind of falls into this bucket of having social jet lag. But one of the things that we, one research study we saw looking at specifically a social jet lag in college students, they saw that for every hour of variability between week, day,

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's like, we can't even see a pattern. It's random, which is frightening. Why is that frightening? Because, you know, the more variability you have, like the more psychological and physiological,

you know, negative consequences there'll be. Is there a correlation here between how we deal with stressful events in our lives as well? Because I'm assuming there must be. Yes, absolutely. Managing stress throughout the day and the degree or even during the night can definitely increase your tolerance for stress. So deploying breathwork, for example, as on-demand self-regulation tool to pay down in the moment stress can be, and to activate the parasitic 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 stakes, high stress environments is an amazing strategy. Because 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 system is humming at a kind of a stress level that is above what would be normal, right? Like 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 bypassed, right? When you're doing exactly the opposite of what your body wants to do. So all of the kind of biological preferences are being bypassed, right?

When you're up during the biological night. So to pay down some of that stress, these many moments of deactivation are absolutely critical for that population. So that means just literally taking 30 seconds where you're doing the physiological sigh, for example, which we know has emerged as being the most efficacious breathwork technique in the moment

to reduce not only in the moment anxiety and stress, but actually your perception of anxiety and stress like in the future. What is that sign? The physiological sigh. It's basically a double inhale followed by an extended exhale. Perfect.

That's exactly right. So basically like when you're crying, you kind of do that double inhale followed by an extended exhale. But that like reduces stress in the moment in a really powerful way. And if you do that five, ten times, you end up activating the parasympathetic branch. So you're reducing your heart rate. And, you know, kind of doing that throughout the day is a great way to mitigate negative stress accumulation. There's a pretty unfortunate paradox, a pretty tragic paradox in the fact that our shift workers, some of them like doctors, especially, are the people that we need to be most focused. Firing on all cylinders.

Exactly. But those are the people that are, from what I've learned today about the circadian rhythm, most likely to suffer with things like focus and sleep and all of those things that are imperative to showing up well. Yeah. I mean, there's a relationship. You know, we know that with every 45 minutes of sleep deprivation accrued on the Woot platform, we see a 5% to 10% next day decrease in mental control. Mental control.

Executive function. So we measure this with an MBAC and a Stroop. So these kind of 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. And what does executive function mean for people that are?

Our ability to make decisions. Okay. Use the word there, sleep debt. What is sleep debt? So that's basically what you need versus what you actually got. And that's highly individual, right? And that's one of the kind of beautiful things on the Woop platform is that we learn 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 team has done specifically at Whoop is to try to understand, you know, what is this relationship 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 was looking specifically at business executives, so CEO types. And we basically looked at, this one was a six-month study, looking at two different cohorts, I think equal distribution between men and women. And what we saw was for every 45 minutes of sleep 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 gets worse the more sleep debt you accrue. We did a follow-up study, and this one was wild. So we basically looked at, it was roughly, it was about 70 business executive CEO types,

and we looked at all of their objective markers, sleep debt being one of them, and we look at the psychological safety of their direct reports during team meetings. And define psychological safety. How safe you feel to show up in your environment as your true, most authentic self. And what we saw is 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 some of these folks were carrying a couple hours of sleep debt. And there was a linear relationship between the amount of psychological safety and the amount of sleep that the leader had. So 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 face, how you emote, the kind of eye contact you make, how tolerant you are. And you think about how sleep deprivation, and I think this is really what this research surfaces, it's not just sleep deprivation just doesn't impact me, right? It's going to impact every single person I come in contact with. And from a business perspective, just from a sheer like numbers perspective, Google did a study called Aristotle, and 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 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 kind of show up as your best self as consistently as possible, minimizing sleep debt is right there at the top of the list. It's fascinating. And as it relates to sort of accident and injury, is there a correlation

between sort of injury of oneself and accidents you commit on others? Correlation between that and sleep debt? It's very well established that the more sleep debt you're carrying, you know, the more accident prone you are, you know, the more risk you're going to take. And yeah, we see this in the medical field, we see this, you know, in, you know, just car accidents. And yeah, the list goes on and on. 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. Yeah. I know. When we think about sleep, we're not getting better at it as a society. And I think we're kind of coming at this conversation from the wrong lens. We're

telling folks just to spend more time in bed without addressing the behaviors that are actually enable us to fall asleep and stay asleep. You know, that's, to me, that's, that's the conversation. And, and it's not about spending more time in bed and yeah, that might be what needs to happen, but it's, it's about, you're not going to get there for folks who, who are not thinking about all the circadian things that we're talking about. And some of the environmental stuff, the cold, dark, the quiet, yes, that matters. But at a foundational level, I think folks are not engaging in the behaviors that are going to enable us to pay down the sleep deprivation.

The other study that I found that was super interesting was that a 2021 study found that less than seven hours of sleep is associated with increased risk of injury. And if this is sustained for at least 14 days, the risk of muscle and bone injury is 1.7 times, almost two times higher. So as someone that goes to the gym a lot and likes to work out, if I have a high sleep debt,

then I'm much more likely to get an injury, almost two times more likely to get an injury if that's sustained that's right which is crazy yeah it is yeah and you know i'm so grateful that i think folks are finally realizing that sleep is the greatest natural performance and answer that we have on this planet um yeah it's and that is certainly super evident in all the research that we're doing. What about sleep and sex? Sex with a partner is a health promoting behavior. And we have found that in our research. What research have you done?

Yeah. I mean, we just, we actually haven't published it yet. So this is preliminary data, but people who are reporting that they're having sex before bed. So within a few hours of when they intend to sleep with a partner have better markers of sleep and recovery. You said with a partner very intentionally though. I did. Yeah. We don't see the same effect when folks are having sex without a partner and reporting it. How do you have sex without a partner? I mean, all right, I should say a partner, like a spouse or a boyfriend or someone who you're consistently with.

So we're talking about, I guess, not one night stands. Sorry, I should have clarified it. I thought you meant without a human at all. Oh, got it. Yeah, I'm talking about human sex here. Yeah. Does masturbation have the same implications? We didn't see big effects with masturbation.

Are people reporting that? They're on Whoop? They sure are. They are? I should say that it is completely optional to track. So people can opt into tracking these things. Again, it is completely de-identified. We have no ability to know who's doing what

in terms of journal tracking and behaviors. But yeah, so we don't actually see any big effects with masturbation and any markers of sleep and recovery. So no strong effects there. We said something earlier about exercising before bed. Now, if I have sex before bed and, you know, it lasts a long time. Yeah. Is that not then going to produce a ton of adrenaline and wake me up again? So after, so it depends.

If you ejaculate, then you will then release oxytocin, which is kind of a calming chemical. So guys typically after they ejaculate feel sleepy because of the release of oxytocin but then that goes back to my point about masturbation don't you release oxytocin when you masturbate yeah i think i think that oxytocin is about connection okay right so it's it's that's i think that's and that might be why we see these strong effects when you're having sex with a partner or a spouse is that you're getting this benefit of this beautiful connection with your partner and spouse, provided it goes well.

And then you release this oxytocin, which is, you know, kind of makes you feel connected and safe. And so all of those, I think that kind of condition helps, I think, you fall asleep and potentially stay asleep. It does make sense because I do get very, very tired after I've had sex with my partner. And I've always wondered why that is. Yeah, and I don't know that women, it seems to have women want to maybe stay up and snuggle and talk a little bit more after sex. But guys, it seems, get sleepy and want to fall asleep.

And or want to run off. Or that. That's a bit of a stereotype. Yeah. That goes back quite far prehistorically. The other thing I would love to talk to you about because it's become a huge obsession in my life is this word, I guess it's not a word, it's an acronym,

HRV, heart rate variability. I've become absolutely obsessed with it. Maybe a little bit too obsessed with it, one might argue. I just check it every day. So the first thing I do when I wake up in the morning is I look at it. Yeah. Just to understand how my body has recovered

from the night before. Right. What is HRV? It's most simply the time interval between heartbeats. And it's a function of the heart, but it originates in the autonomic nervous system. And as we've talked about, the autonomic nervous system has two branches,

the parasympathetic and the sympathetic. Parasympathetic, 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 heart is going to be responsive to both branches of that autonomic nervous system in a very kind of dynamic way. So whatever you want to do and what's happening in your environment, you're able to basically make a match the more recovered you are, if that makes sense. So you'll be able to respond and react to environmental stress in kind of a more high-performing way, I suppose is the best way to say it. So heart variability is kind of a measure of that ability to adapt to your environment in a functional way. And a high heart rate variability, which is more varying beats, heartbeats, is better.

Yeah, more variability, the better. So higher heart rate variability should be correlated with better adaptation to environmental stress. So a low heart rate variability would sound something like this. Bum, bum, bum, bum, bum. That's exactly right. Very, very consistent. Not good. Right. A high heart rate variability will sound like bum, bum, bum, bum, bum.

So really varied. Perfect. Beautiful, beautiful description. Paradoxical that variation is better? Yeah. You'd think that if something was consistent, it would be better. I know. In all other cases, it is. But in the case of heart rate variability, it's very counterintuitive. And what's great is heart rate variability is modifiable to a degree.

What's an average heart rate variability? So it's all based on genetics. It's really tough, right? Because I don't know what your heart rate variability was when you were born, right? So I don't know what your potential for heart rate variability is. And I think that's the only thing that I think we can say, and I think how people need to think about it is when you come onto the Woot platform, for example, you're going to get your heart rate variability. You're going to develop a baseline. And I think what people need to understand is that every behavior, every choice you've kind of made leading up to that moment is going to determine like your baseline heart rate variability. So if you, you know, drank and

take drugs and have a lot of childhood trauma, that might actually yield a lower baseline heart rate variability relative to your own potential, right? So it's very hard to compare because of all of that, but then just genetics, heart size, gender, like all of those things, biological sex, all of those things have an impact on your heart rate variability, on your baseline. So you don't want to compare. There's no good. That said, I think the higher, the better, generally. What's the average? Well, it depends on age. So it decreases, you know, every year your heart rate variability is going to decrease a bit. I think it's like three to 4% or something, which is kind of a lot. Yeah. The

average on the platform, you know, from the 20 to 30 year olds is somewhere in the tune of, of kind of 65, 70, 30 to 40 year olds, a little bit lower, 40 to 50s. It's kind of in the 50s range, I think. So definitely gets worse as you age. But I think why people are obsessed about it is it's just, it is a really good marker of just the overall state of your mental, physical, and emotional health. Do women and men have variants in their heart? They do, yeah. So generally men would have higher heart rate variability than women, I think at baseline, bigger heart size. I'm trying to get my heart rate variability up. What are the most important things for me to be thinking about?

Because it seems to be a bit of a mystery, this heart rate variability thing. So there's definitely some things that will directly impact your heart rate variability. Sleep-wake time. So stabilizing when you go to bed to wake up, wake onset being kind of the number one priority. You want to wake up at a regular time every single day. You want to get a huge ball of light as soon as you wake up. You want to get a lot of natural light during the day. Okay. All of these things are going to impact inflammation and cortisol, like all of the things that are kind of circulating in our body that we need to be circulating. And when we're not doing some of

these behaviors, they're not circulating in our body, which have negative downstream effects. You want to mitigate stress throughout the day. So stress is not bad, but we need to proactively manage bouts of stress with appropriate levels of rest, right? When we are going, going, going, and we can only sustain that for so long. So just being proactive with stress rest cycles throughout the day, really important. As we go, we want to eat a bulk of our calories in the morning, lots and lots of protein. We want to make sure that we get lots of protein. I think folks don't probably get enough protein. We want to get lots of protein.

Bias early in the day. Stop eating a few hours before bedtime. And make sure you're hydrated throughout the day. Yes, absolutely. So I can go down a very deep rabbit hole in terms of optimal training protocols. But in sum, we want to make sure that we're polarizing our training in that we're doing zone five,

which is kind of max effort where we're out of breath a couple times a week, okay? Two to three times a week. And then we want to do zone two, which is kind of just a low level, 60% of our max heart rate. We want to do that for 200 to 300 minutes per week, which I know sounds like a lot. The recommendations, 150 minutes, I think it's a little, I don't think that's enough, frankly, but if we're talking about optimizing heart rate variability, that would be the protocol. We want to strength train a few times a week.

That would be a way to maximize interplay between the cardiovascular and the nervous system, right? There is definitely a way to train to do that. And what I just described will kind of get you there roughly. So we talked about time-restricted eating or stopping our feeding window three hours before we intend to sleep. Huge. No alcohol, obviously. Again, if we're interested in optimizing our ability to adapt to environmental stress, that is an improve our heart rate variability, really important we abstain

from alcohol. And then i would say you know spending sufficient time in bed is going to be really important that is not accumulating uh sleep debt yeah that's the laundry list what about having friends yes connection you know folks being around individuals who support your values um is absolutely essential We talked a little bit about exercise there, but there's also just like the general sedentary-ness of our lives. I was looking at some research a couple of years ago, which I included in my first book, which shows that in the Western world,

we're getting increasingly more sedentary. It's kind of like this downward graph that just shows every year people move less because we've got Ubers now and we're working more in offices and we're working even more from home now and we're optimizing activity out of our lives. And surely that has an implication for heart variability as well. There's no question that sedentary behavior, you know, I think where we go wrong is we think I can wake up and work out for an hour, and then that gives me license to sit for the rest of the day. But we know that for individuals who are sitting for more than four hours in a row,

so consolidated sitting for four-hour blocks is associated with increased mortality rates. So four hours of sedentary behavior, which consolidated, right? So the ideal protocol, if we want to basically improve all these parameters of health that we're talking about, specifically heart rate variability, you want to break up your sedentary time. So every half an hour to an hour, you'd want to get up, move around for five minutes or so, and then get back to your work. In 2020, you wrote an article where you offered five ways to improve our HRV. And HRV, as I say, is super important because it's linked to all of these health markers. It's linked to immunity. It's linked to all of these things that really, really

matter. And one of the, there was a couple of sort of surprising suggestions you made in that article. One of them was about practicing gratitude. Yeah. I mean, I think, I think what the research says is that actually receiving gratitude has the most powerful effect on our, on our mood and our feelings of well-being. So if I were to receive a thank you letter, for example, and really internalize that, that's going to have the biggest long-term effect on my feelings of well-being. But there's also great research that shows giving thanks as well and expressing gratitude also has lots of positive implications for our psychological functioning. And I guess this brings into focus the psychological element of health and HRV and sleep and all of these things that we've talked about, like stress and

anxiety. You're currently finishing a PhD in psychology, right? That's right. Yes. And again, it links to something that was written in that article as well, where you talk about a growth mindset. Again, that's psychology. Yes. Why does this matter? This growth mindset thing,

this gratitude psychology, why does that matter? Yeah, I mean, I think it relates to just our, whether or not we feel that growth in the future is possible. You know, do we feel like we have the potential to grow and to learn? And do we feel optimistic about the future? I mean, that's really what growth mindset is, right? And you can imagine if you don't feel optimistic about the future, you don't feel like growth is possible.

You feel really limited in your capabilities, right? And you feel limited in your happiness. So I think that, yeah, there's, I think, a really strong connection between believing that the future is positive and that is going to manifest in a measure like heart rate variability. It's going to manifest physiologically. There's this author called Sean Anker. Oh, Sean Aker, yeah, from Harvard. Do I butcher his name? Yeah, Aker. He does a lot of work on this idea of growth mindset as a way to sort of counteract stress,

which I find fascinating. He does, yeah. He found that doctors in a positive state of mind perform diagnoses 19% faster and more accurately than doctors that are neutral. And he also found that positive employees are 31% more productive than negative employees. Yeah. And I think our life circumstance, you know, kind of certainly can tilt us in one direction or another, but I do think that we have a genetic predisposition to the cup is half empty versus half full. I think there's something to that research

and that literature, but all the things that we're talking about, I think provide a foundation, right? So a lot of the physiological stuff that we're talking about, I think provide a foundation, right? So a lot of the physiological stuff that we're talking about, the circadian stuff, the sleep stuff, the recovery stuff, right? The stress management, you know, when we're eating our food, the, how we're training, right? All of these things kind of position us to, I think, leverage our, our mindsets in a way that is the most productive, right? When we're not kind of taking care of these physiological things, you know, we don't feel like we have purpose. We talked about this. We don't feel the skills and resources to do the things that we want to

do in our life. It's really hard to talk ourselves into a better future, right? And, and it's, it's hard to kind of move around our mindset, but if we can just kind of attend to some of these physiological and psychological things, we can actually start to take more control of our mindset. So I think a lot of times, and this is, I think frustrating in the field of psychology, we talk about how we talk about growth mindset without actually talking about the behaviors that actually underpin that, you know's, I think, a lot of the work that I'm trying to do is that there's these core influences, physiological and psychological, that if we can understand and build an infrastructure to allow those kind of behaviors

to come to life in our every day, we're in a position then to have like a growth mindset, right? But without that, that, that foundation of good habits and good behaviors, good habits and behaviors, it's hard to believe that the future is, is bright. It brings into question something that I know a lot of people think when they hear conversations like this, they think, oh, but I just don't have the motivation Kristen you know and there's this ongoing conversation about which comes first is it the action or is it the motivation there's clearly in my life I've seen this clear two-way link by through what I do and how I feel and how I feel and what I do yeah so if I want to influence the other I do the other I if I want to feel great, I have to focus on my actions.

And if I want to act great, I'll focus on how I feel, for example, you know what I mean? Because people hear, you know, the discipline that you practice in your life and they go, you must have so much motivation. You know, the people that are watching junk TV at 3am in the morning and eating junk food at 3am in the morning, they look at you and go, she's got just, she just got something I just haven't got. So I can't relate. You know, I can't become a Kristen. What is the message those people need to hear? The ones that feel like motivation is their problem. I mean, I think it's understanding how do we actually produce energy, right? Because that's really at the core of what motivation is, right?

It's the energy, right? And a couple of things influence our energy production or put a ceiling on motivation. It's called, well, it's appraisal. So how relevant we think a task is and then how we are perceiving the task. Is it hard? Is it easy? Is it challenging? Right? So appraisal and perception are going to work together to put a ceiling on your potential for motivation okay so appraisal i hear is being like the why why this matters totally that's how relevant is it to me so interesting because in my book i wrote this thing called the discipline equation and i think you know i think you've kind of summarized it a little bit there yeah yeah

yeah definitely i mean this is well understood? In the field of psychology and physiology that, yeah, we all have potential motivation. And the two things that move around is how we appraise the situation and how we perceive it. So in my discipline equation, this is the equation, discipline equals the strength of one's why plus the reward of the pursuit minus the cost of the pursuit. Perfect. I love that. Yeah. That's beautiful. And I think that would hold, that holds up clearly.

Because I saw the fucking book. Yeah. Oh my God, you said that. Yeah. No, for sure. But I think, and I would, I said, you know, one of the reasons why I think my teams were always so successful is I just deployed that principle over and over again in my environment. How? I helped my athletes understand the why, their personal why. Like, why were they showing up every single day to the field?

How was that attached to their individual values? Not my team values, to their personal values, right? And then I made the environment challenging, right? So they get excited about the work that they're doing every day, right? And I try to do that on an individual level. And that's why a lot of teams underperform, frankly, is that leaders don't understand the relationship

between appraisal and perception. Like I literally think if you can understand that and you've written a book about it, right? So people can read this book and if leaders can adopt and understand the importance of setting, of creating an infrastructure where you tap into the person's individual values and how that relates to the task, you have motivation. Like you will increase the ceiling for potential motivation. It makes me think in some ways that people listening to this right now are, without knowing it, in a upward reinforcing spiral towards the person they want to be, or in a downward

reinforcing spiral away from the person they want to be. Because if you're showing up and acting in the right way, then you're going to release energy, you're going to feel good, which means you have a better chance of showing up and acting in the right way. And that spiral goes upwards. But if you're showing up in the wrong way, it means you're probably going to be a little bit depressed. You're going to have a lot of circadian disruption. You're not going to feel great, which means you have less chance of showing up in the right way. You don't have the energy. Low energy, all of those things. It's a downward spiral.

So if you're in that downward spiral, I would guess the way, the only way to break out of it, I mean, is you listen to a podcast, but that's not going to help you break out of it alone. It's going to start with you making one different decision at one point. And that can be a tiny, tiny, tiny decision. Yeah. And I think that's a lot of the work I'm doing right now is trying to figure out what is that actual taxonomy though? If someone really wants to make change, where do they start?

Where do they start? You know, I'm going to say it. Sleep-wake time. Like wake up at the same time every day and get as much as light as humanly possible. That will set the tone for the rest of the day and put you in a position where you can fall asleep at a regular time, night after night. You have to address that. The second thing is I would consolidate your eating window. Keep it within a 10-hour time frame. Eat all of your calories within a 10-hour time frame and try to leave a couple-hour buffer between when you tend to sleep and your last calorie. Just those two things are pretty low barrier to entry, right? And that will increase mood. You'll improve your body composition, right? Just by narrowing that window, you will, you know, all the effects that we talked about in terms of the cardio and metabolic effects from just stabilizing sleep-wake time, the mood effects from stabilizing sleep-wake time,

that will back you into having a better relationship with light, right? Which we know light is at the core of human health and functioning. So those two things I would say is the place to start. And I think the downstream effect of just those two things is pretty profound. And then I think in parallel, just figuring out who do you actually want to be in the world? What do you want your identity to be? And I don't know that people actually think enough about that. There's so many distractions in this world. I mean, we can just drown ourselves with just stuff that's just coming at us, content all the time. And we can't discern, we haven't done the work to be able to discern what is actually important to

us. We don't have the capacity to direct our thoughts and our attention in a way that's rewarding, right? Because we haven't built that skill or that muscle. So I think like getting that under control is another way is like really figuring out what is my relationship with technology? Like, what do I want that to be? You know, how do I actually want to spend my time? Have you written that down? For sure. Absolutely. And what format does that take or what medium did you use? Is that a vision board or something? Oh, just like pen and paper. I mean, I have, yeah, I mean, Evernote, you know, I revisit this quarterly. You know, what do I value? What do I care about? How do I want to spend my time? And that has been the basis for which I make all my decisions. What does your Evernote say? Oh, I mean, in terms of like my, how I think that why I have my list of values, right? That it

always starts there, right? What are your values? So growth, impact, tolerance, compassion, and presence. Those are my top five values. And I meditate on those. I, whenever I, you know, I'll look for, I have some of my favorite authors that have written extensively about all those different things, like, you know, James Baldwin on compassion and tolerance and Ayn Rand on impact and growth. I love her work. But yeah, I mean, I think really connecting to what do those beliefs and values actually look like in action, right? If I don't know what growth looks like, if I don't know what tolerance looks like in action, how do I actually play that out in my day-to-day, right? So you have to write about it.

You have to internalize it. And then you have to practice that behavior, right? So in my Evernote, I have a kind of like, what does this look like in action? Like, what are the things that I can do that I can practice to live these values? And then it's having an outlet for those things. What kind of things do I need to do? Like my PhD, that's not a goal. I don't have any goals. Like goals are total BS in my view. It's like living your values. Like my PhD allows me to live my values of growth and impact, right? If I want to impact health at scale, I need to have the credibility. I need to know how to run experiments. I need to be a scientist, right? And so it's not, yeah, I'm reaching this goal of getting a PhD, but it's allowing me to live my values of growth and impact.

And I think that's where folks kind of get it wrong is they're like, I want to run a 10K. And then what happens after you run the 10K? And I use that principle in my life. Like I'm not, it's like, I'm always just trying to live my values and I don't evaluate success on like achieving something. It's all about my scorecard is, am I living my values to my fullest? Like that to me is a win. And that's how I evaluated my environment when I was coaching collegiately. It was like, are we living our values? And when you do that, you kind of always win, you know? And it has a kind of second order effect in terms of how you think about competition,

right? Like that's another area where like, I don't compete. I stopped competing a decade and a half ago. Like we wouldn't even like our, when we know my team at Princeton, like these are just little things, but when we talk about going back to like an infrastructure to support your values, like we didn't even list our opponents. Like I didn't want them thinking about how, I didn't want them like changing how they acted throughout the week, how they trained, the quality, what they did behaviorally based on our opponent. That didn't matter, right? If you want to perform consistently, you need to show up every single day with quality, right? And being willing to apply yourself in a way that is going to create the output

that leads to the kind of quality that allows you to replicate performance levels. And it's about learning and development and it wasn't about an opponent, right? And that's why teams underperform, right? That's why individuals underperform is they've got this arbitrary kind of metric that they're like team that they wanna beat

that they're focused on, right? Or person that they wanna beat that they're focused on. Instead of looking, okay, what is my bar? Like, and going back to that question, am I actually living my values? I think everything kind of works itself out if you can just do that. Kristen, we have a closing tradition on this podcast

where the last guest leaves a question for the next guest, not knowing who they're going to be leaving it for. The question that has been left for you, what is the last thing that you would say? And I imagine the context though, and this is just me taking a guess, is that if there was a last thing that you had to say, what is the last thing that you would say? I think figure out who you want to be in the world and then set up your life so you can be that person. Kristen, thank you.

So incredibly inspiring in so many ways. I would promote Whoop, but I feel like you already have just by being so inspiring, so smart, so wise. And that's, I mean, everything that Whoop is in a nutshell. There's so many thank yous that I want to give you for so many different reasons. But I think the most important thank you that I'll give you is for both the hundreds and thousands of lives that your work has nudged in a better direction and transformed in many cases, but also for the millions and millions and hundreds of millions of lives

that you're going to nudge in a much better direction over the course of the next decade and decade and decade and decade. It's a tremendous service to humanity, having the potential service to humanity, having the skills, the storytelling abilities, the wisdom, and that deep innate sense of drive that you have. And it is a service to humanity

that humanity increasingly, unfortunately, needs. And I'm so excited to watch that play out for you. I deeply believe this is the very start of your journey in many respects, even though you're several decades into the work that you do. But there's something tells me that this is just the beginning. So Kristen, thank you for your generosity. Thank you for your wisdom. And thank you for your time. Appreciate you. I appreciate you so much, Stephen.

Thank you for all your good work.