Kristen (00:00)
what I see in division one athletes,
presumably some of the most robust individuals, athletes on the planet, they seem to be able to get away with only 45 minutes of variability before we see a decline in resting physiology. So we're, we're a little bit more sensitive, unfortunately, than than what we might realize, right?
Paul Warloski (00:45)
Hello and welcome to the Athletes Compass Podcast, where we navigate training, fitness, and health for everyday athletes. Today we get to talk with Dr. Kristen Holmes, who is the global head of human performance at Whoop, where she translates physiological and behavioral data into practical strategies that improve health, performance, and well-being. Her research has helped identify novel digital biomarkers, including sleep HRV analyses.
And has advanced understanding of maternal physiology through wearable technology. Before joining Whoop, Holmes was a Hall of Fame athlete at the University of Iowa, a member of the U.S. national field hockey team, and one of the most successful coaches in Ivy League history, leading Princeton University to 12 league titles and an NCAA championship. Congratulations, by the way.
Kristen (01:37)
Thanks.
Paul Warloski (01:37)
She holds a PhD
in psychology from the University of Queensland and is a widely sought after speaker on sleep recovery and wearable technology, women's health and human performance. Kristen, welcome to the Athletes Compass Podcast.
Kristen (01:51)
Well, thank you so much for having me. I'm such a fan of of your everyone's work on this on this call right now. So yeah, I'm super grateful to be here.
Paul Warloski (02:01)
Awesome. Kristen, you have studied sleep data from nearly 20,000 athletes using Whoop. What's the one finding that surprised you the most?
Kristen (02:12)
Yeah, well, you know, I've been inside athlete data specifically since 2016. So I've been at Whoop for for a decade, which is kind of wild. But, you know, one of the very first, you know, there's a paper that was published in 2017 by Dr. Andrew Phillips from Manache. And he looked at he was looking at Harvard, Harvard students and analyzing their sleep. And he had, their their academic records and
The one thing that predicted academic performance was sleepwake consistency. So this was kind of a landmark paper in 2017. And, basically correlating sleep wake regularity, what he calls it, and he created the sleep regularity index, correlating it to GPA. And at the time I was working with a lot of NC2A collegiate athletes. And so I started at at the time at Whoop, we didn't, we actually didn't
measure consistency, which is which is quite literally when you go to bed and when you wake up and the degree to which that's consistent. And you can look at we look at a rolling average of four to five days and to determine how consistent your your sleep wake is. But at the time we weren't measuring it. And so I started manually measuring sleep weight consistency across the athletes that I was working with. So at the time I was working with probably 1500 I would say NC2A
Division one athletes. and and I started, you know, looking at sleepweight consistency and and then we started looking at other performance metrics, you know, and that that folks in these respective sports care about. And the the one thing when I analyzed all of the data, so all the autonomic data, you know, all the different kinds of sleep data, sleep weight consistently, consistently bubbled up as being predictive or associated with performance metrics we care about.
So this was, you know, 2018, 2019. And we we ended up productizing sleepweight consistency because it was like such an incredible, you know, I guess, behavior that was associated with all of the performance metrics we we care about. And we ended up actually publishing a paper recently where we're able to kind of replicate this effect with professional golfers.
So you know, a lot of the data that I was looking was, even professional athletes like ice hockey efficiency, time in the pool, swim times, like speed, and and track and field athletes. So just looking at, just sprint times, free throw percentage, I mean, exit bat velocity, exit ball velocity, like every like metric you care about was associated with sleepweight consistency. So
To me, that was so surprising that that sleepweight consistency bubbled up as kind of the mother of all behaviors as it relates to performance.
Paul Laursen (05:01)
Yeah.
I I love that. I I hope I can I I'm just gonna chime in there with my own little personal anecdote with that. So many many of the listeners will know I've got my daughter Kaya, who she's a sixteen year old top swimmer in my in my in our province. And she had well she had a we had a bunch of sleep issues that were just happening. One she she had a party to go to with her friends and so we you know
Kristen (05:16)
Wow.
Paul Laursen (05:28)
But it that social factor is important, so we let her go to that. If stayed up late, and then fire alarms, whatever, they went off in the in the house over overnight. Long story short, her sleep was very, very poor. And her first two events at the swim meet over this last weekend were actually below below p below par, below standard. We're kinda wondering a little bit why, but I think it really speaks to then she sort of sort of warmed up a as she went went through, but the morning performances were just totally off, Kristen.
Kristen (05:57)
Compromise.
Yeah. I mean, it's it it it it and what we see, and we know from Daniel Windred has published a lot in this area. he's a sleep and circadian scientist. And he he published a really a landmark paper in in January of 2024, he and his colleagues, where basically they found sleepweight consistency was a greater predictor of all-cause mortality than sleep duration, even. So just that, you know, and and what I see in division one athletes, you know.
Paul Laursen (05:59)
Yeah.
Kristen (06:27)
presumably some of the most robust individuals, athletes on the planet, you know, 18 to 23 year olds, they seem to be able to get away with only 45 minutes of variability before we see a decline in resting physiology. So we're, we're a little bit more sensitive, unfortunately, than than what we might realize, right? And and I think one of the biggest natural experiments, of course, is when we shift daylight savings and, you know, and we have to spring back, that is it's the
Paul Laursen (06:47)
Yeah.
Kristen (06:56)
I think the time frame the the day where we have the most cardiovascular events globally, people, you know, for the for the folks who engage in in this, time change in the spring, the spring back. So we know that systems that are already vulnerable, when you do kind of force a wake up an hour before, the typical wake up time, it creates a lot of stress on the system, hence all these cardiovascular events that are occurring on that day.
So yeah.
Marjaana Rakai (07:25)
Wow,
this is super interesting because so I understand that what you've learned is that it's the sleep consistency instead of sleep quality that matters for performance metrics. And you could see like if you go to any youth sports tournaments, especially like south like Southern states like Texas
Sometimes the kids are playing still like eleven PM and then Sunday morning hits and they need to be at the field at seven and you can tell that the kids are not ready for perform at all. But this is super interesting because I've always told my athletes that I coach that, you know, like the night before race, you you'll be fine, like because
Kristen (08:02)
I know.
Marjaana Rakai (08:14)
When you do Iron Man events, you have to sometimes get up at three o'clock, right? So that sleep consistency is totally interrupted. so maybe I've been wrong all these years.
Kristen (08:18)
Yeah, totally.
Well,
I you know, sleep sleepweight consistency actually drives sleep quality. And that's what makes it, I think, such a important behavior is that, you know, we see very strong a very strong relationship between consistency and quality of sleep. And we know that autonomic robustness, HRV, is literally correlated with sleep quality, right? That's like the one sleep
Paul Laursen (08:28)
No.
Mm-hmm.
Kristen (08:55)
kind of metric that we can associate with heart rate variability. So, so I think the the point is they all all of it matters, right? Timing matters, sufficiency matters, consistency matters, quality matters, all four pillars matter. But I think it's understanding that sleep consistency is actually the driver of of restoration. And I think that's what we kind of miss in the performance space and the health space, honestly.
Paul Laursen (09:21)
Nice. So why don't we why don't we stick there and and finish this one up there there, Kristen So we can we believe you. tr you know, sleep consistency leads to better sleep quality. What can what is the practical takeaways that that a listener can can start start to do to to drive their own sleep consistency and quality?
Kristen (09:43)
Yeah, so you know, I ran like I I did a kind of a quasi experiment. you know, I wasn't able to randomly assign folks because this was a really large real world experiment, but I had about 39,000 folks per participate in an experiment that I ran to try to figure out if any of these very simple practical behaviors that are related to.
kind of our circadian rhythms, if that would have any impact on sleep weight consistency. And the reason I ran this experiment is because when I look at all of our data on Whoop, sleep weight consistency is, given how much we kind of yell at our members that it matters, it still is really hard. You know, I think the average sleepweight consistency is 68%.
So we express it as a percentage. So that's low, right? And I and I think it's actually improved by four percent over the course of the last couple of years. So we are getting better.
MJ, you know, you bring up a great point. Like modern society isn't doesn't really set us up for success when it as it relates to sleep weight consistency, right? It's just a really hard behavior to adapt adopt. So I wondered, you know, in in in my kind of sleep and circadian studies, I I recognize that there are certain behaviors that really can help facilitate sleep weight consistency. So I ran an experiment where I
asked folks to the extent that they can over the course of a month, engage in any or all of these four behaviors. And one was viewing morning sunlight, which sets the circadian rhythm, engaging in moderate level of activity. I can't even call it zone to exercise because that's another conversation, but I could go on for days about that it's not even exercise, it's a recovery modality. But that's a separate data set, which I'm happy to talk about. But
Paul Laursen (11:26)
Hmm.
Kristen (11:41)
But but zone two, I I kind of that moderate level of activity, because it's so recovery promoting, it deactivates the nervous system in such a powerful way. This is what I've observed in my own data and the data of millions of people. I can say that it is unequivocally a recovery modality, which I was trying to help facilitate, right? If we're if we're putting if we're if we are engaging in really intense vigorous activity consistently without requisite amounts of kind of recovery built in, recovery type of
activity, then sleepweak insistency will be harder to achieve even if we're trying to do that. So moderate level activity and then some breath work, which has been shown, slow-paced breathing can kind of deactivate the nervous system, kind of puts you in a more sort of state, helping to facilitate sleep. And then finally time restricted eating, which has a very clear circadian component to it.
It is not intermittent fasting and can go down that rabbit hole if you wish, wish, but I really think we need to separate time-restricted eating, which has a circating component. It is about eating whilst the sun is up, to the extent that you can, 12 hours on, basically, where you're intaking all of your calories, 12 hours off, ideally when the sun is up. And that's what I recommended to the folks who are engaging in this in this experiment. and then, and so those are the four core behaviors. And what we saw.
is that the individuals who engaged in these behaviors improved sleep weight consistency. So these behaviors helped to facilitate in a statistically meeting a way their sleepweight consistency, which in turn impacted or improved their cardiorespiratory fitness and parasynthetic activation. So we saw this really powerful autonomic kind of effect, which was awesome. They had a de increase in in
Paul Laursen (13:25)
Hm.
Kristen (13:35)
Heart rate variability over the course of this experiment. and we also saw their resting heart rate improve as well, which was which was really cool. so you know, we saw these markers of cardiosparifness improve. So it was just a very simple experiment, but I think in today's day and age, where I think we lose the plot a little bit in terms of like making things really complicated, it is just these basic, very basic behaviors that are democratically available and free.
You don't have to pay a dime for any of these four behaviors, but they actually help facilitate, they create conditions that allow you to have a more stable sleep wake time. Because if I just said, if MJ, you just said, I want to go to bed at 10 p.m., but you haven't really set up your day in a way to in that your circadian rhythms are aligned with a 10 p.m. sleep, then going to bed at 10 p.m. becomes very difficult, right? So people can want to do that, but don't realize that it's actually the daytime behaviors.
that create the conditions that allow for a stable sleep wake time.
Paul Laursen (14:39)
Wow, I love that. But I mean let's just let's just review them. again, all things that you're empowered the listener to be able to do this. first first and foremost, depending on the time of year, right? And if we're in the vi high northern hemisphere or southern hemisphere, light on the light in the eyes is could be could be difficult. But for the majority I guess of us on living on the planet, most times of years
Marjaana Rakai (14:41)
Yeah.
Kristen (14:41)
Yeah.
Paul Laursen (15:04)
Very first thing, easy. Just get that sunlight in the in the eyes, or or just the it doesn't have to be sunlight in the eyes, but just like daylight. Just natural light. yeah, as opposed probably as opposed to blue light. Maybe even, you know, don't be in a dark room staring at your screen if it's you know, if there's sort of sunlight outside. there's probably you know, fifteen minutes in the in the daylight is probably gonna be like factor number one that's gonna gonna change everything for you.
Kristen (15:08)
Yeah. Yeah. Just natural light. Natural light that
For sure.
For sure, it is such an important anchor for your circadian system. And I and I it's and I when we really like zoom out and like we look at how many folks struggle from chronic disease, a lot of it is tied to the fact that we are pulled from these primal thresholds of nature.
You know, and and I'm definitely not that one where like, everything that happened on the savannah was awesome. I you know, people are dying at 30. Okay. I I'm not saying that. Modern medicine's really important, but I think that the fact that we struggle as a, you know, certainly in in North America, right? When we when we talk about just the the you know, the the level, I mean it's epidemic proportions, right? Of of just like people dealing with chronic conditions. And I think a lot of it is that we're just not getting outside. We're not
Our systems are confused, right? And when we view light in the morning, you know, close to when we wake up, we then tell our bodies that we give it important information, right? We we our cells are are basically have an opportunity to be regulated to that natural light dark cycle. And and that sets off a cascade of communication between the cells. And and let's just be very clear, disease.
Progression and you know, just making you vulnerable to disease is basically cells miscommunicating. So when we bypass these kind of circadian behaviors, these behaviors that are line our circadian system, we create cellular confusion. And that is the basis for aging and disease.
Paul Warloski (17:14)
Yeah.
Paul Laursen (17:18)
Yeah, amazing. So next n next item that goes to improve those better those processes is the zone two or recovery intensity, even zone one probably. you know, and we've had Steven Seiler and Phil Maftone tell us the same on the podcast.
Paul Warloski (17:18)
Well.
Kristen (17:34)
Yeah.
Paul Laursen (17:41)
And we know the heart rate variability data as well where this facilitates an increase in HR V in general, whereas high intensity training can can do the opposite potentially. So yeah.
Kristen (17:53)
Right. And it's important,
obviously, to sprinkle in that high intensity. No question. We know that, right? You know, you a couple times, three times a week, depending on, you know, what your baseline capacity is, super important to get that high intensity work in. But what we see in the data, there is no question that, you know, these lower kind of you know levels, these moderate levels of activity are very, very recovery promoting. And when we and and this is, you know, this is when I look at the data and I
Paul Laursen (17:57)
Totally.
Kristen (18:21)
control for a lot of the any of the possible confounders, right? I mean, I'm still left with an enormous data set. And and when you engage in ZO2, the chance of your resting physiology improves. That night are very, very strong. So it it it definitely, yeah, it's it's very good. It's very good.
Paul Warloski (18:39)
Yeah.
Paul Laursen (18:43)
Awesome. Well we're all about that with Athletica and that's why we prescribe it as well. this is a this is this this next one I use personally. So I've had in the context, I've had a really stressful day for for whatever reason, and I can't kind of calm myself down. And I move to your th your third pillar there, which is the breath work. And that's just something, again, like you said, it's in my control. I'm gonna focus on my breath.
Kristen (18:46)
I like it
Yep, I love that. And I, you know, I as I've been telling my I have two children, I've been telling this since telling them since they knew how to talk, you know, that you always have your breath, you know, and and that's something that you can control. And having control of your physiology is one of the greatest superpowers we have. And so engaging in this slow-paced breathing after moments of stress, and it can be good stress, right? Like this is a great stress, you know, but afterwards.
I'll do some slow-paced breathing just to get myself back to neutral, right? So I'm not accumulating stress across the day because that's when it rears its head is at the end of the day when we can't quite settle down. And that's not usually a commentary on how we've engaged in the hour leading up to bed necessarily. It's more of a commentary on how we've engaged in the day, right? So being able to build in these mini moments of slow-paced breathing, of deactivation where we're
We're proactively reducing our heart rate is is is I think an important strategy to having more control over your autonomic nervous system, right? And and ensuring that you are
Again, creating conditions where you're managing your stress levels in ways that allow you, I think, in the evening to kind of show up your for your family in in a way that you want to, you know, and I think we don't always associate again how we're managing our day with with how we show up in the evening when we're when we're there are the families, but that's how I think about it, you know, and that motivates me to ensure that I'm building in those that rest. But also I think importantly for this study is that slow paced breathing.
and building that in proactively would actually help with sleep onset. So again, you know, one of those ways to kind of connect the the daytime stress levels with nighttime stress levels and our ability to kind of fall asleep at a time that's generally, you know, similar to what it was yesterday.
Paul Laursen (21:07)
Yeah, yeah. I love it. But again, in your control. The last one, just to close the loop on this on this topic, this is fascinating. the time restricted eating one. So why is it that if it's better ultimately, really simply, it's better to eat in the daylight? Is that is that kind of it?
Kristen (21:11)
Mm.
Yeah. And and you know, and and there's lots of talk online about this as well. And you know, there I I will just say that, you know, Mike Ormsby's lab down at Florida State University has done some really good work showing that, you know, some protein before well, let me back up and just define time restricted eating. It's essentially just exactly what you said, Paul, just basically prioritizing all of your calories during the daylight hours, right? You know, give or take an hour or so at at either end. But generally speaking, you wanna be
Eating all your calories inside a 12 hour window. So then you're giving your body 12 hours of fasting where you're not eating, right? Where you're allowing all of these recovery processes to happen, right? Because essentially digestion is a parasympathetic endeavor. Okay. It it it needs it's it's gonna, you know, it's rest and digest, right? It's you have to slow your heart rate in order to digest food properly. so when sleep is also
A parasympathetic activity. So these two functions will compete with one another. So if you're eating a really dense, you know, high calorie kind of meal prior to when you intend to sleep, that will impair potentially that first part of your sleep. Because again, your body is prioritizing digestion, is not able to get into these deeper stages of sleep potentially, where there's a lot of important functions happening.
Paul Warloski (22:27)
You know.
Kristen (22:51)
and you know in terms of s you know slow sleep and you know what's happening at the front end your sleep. so these two kind of competing forces, I I think, you know, if if if it's happening a lot will compound and and have an impact on performance and health. and so yeah, getting your all of your calories in that twelve hour window, I think, is is is great. that said, you know, from Mike Orb Ormsby's lab, we do know that some
protein high in and casein doesn't seem to impact 30 minutes prior to bed, doesn't seem to impact markers of sleep or recovery. So if you are not able to appropriately distribute your macronutrients across the day, or you're doing double sessions, or you know, you're a really intense athlete, yeah, you can have some protein before bed and it's not gonna be a big deal.
But when we're talking about just regular folks who, you know, whose willpower might be, you know, not as good right before bed. And, you know, they might have that, you know, cup of yogurt, but then they're like, I want to keep eating, you know. the 12 hour rule can be just really empowering and that you're like, all right, this is just this I'm eating all my calories during this time frame, and then I'm giving my body an opportunity to rest the other. It kind of removes that decision making that can be fatiguing.
Marjaana Rakai (24:08)
I'm I'm listening to all of this and so for Kristen for background, I'm from northern Finland, so way above the Arctic Circle. And granted, this is just a subset of a few million people, but you know, like summertime the sun doesn't set. So it's it's bright day round, night round, like it's 24 hours sunlight.
Kristen (24:15)
Mm. Yeah.
Paul Laursen (24:17)
Yeah.
Marjaana Rakai (24:34)
And then opposite in December, January, it's pitch black with the like this beautiful blue light for a few hours during the day. Have you looked at people or athletes how their sleep rhythm and circadian rhythm
change throughout the four seasons and do these four pillars apply to them? I'm sorry to throw you the into this really minor set
Kristen (25:00)
Yeah.
No, no, no. I actually
the
Paul Laursen (25:07)
Yeah.
Kristen (25:07)
very first paper I published was I looked at a thousand paratroopers from Alaska. I a lot of experience thinking about this this population.
what we saw in this in this data set is that individuals, despite all of the challenges that you just outlined, MJ, which absolutely exist in Alaska in the same way that they do in Finland, the individuals who just maintained a stable sleep wake time seemed to bypass all the deleterious mental and physical outcomes that we would expect.
people would be, in in incurring in in this northern latitude and, these very kind of harsh shifts of season. so and we actually looked at, we didn't just look at kind of the physiological parameters, but we also looked at the psychological parameters. So just their ability to manage the the operational tempo of the environment. we looked at different resilience factors. We looked at their feelings of purpose and control and
And we saw a really strong relationship between you know, a statistically significant relationship, and we set a really high bar in terms of our our threshold between sleepweight consistency and the psychological parameters. So again, it's you know, it's not just physiology, but it's also psychological functioning that is impacted by super variable sleepweight consistency. So MJ, I think the
takeaway is try to maintain despite the the the really stark I think contrasts or the really high levels of exposure of light across the in in 24 hour day and and darkness over twenty four hour day you know if you can kind of maintain this regular cycle you'll be able to bypass a lot of the negative outcomes.
Marjaana Rakai (26:58)
Yeah. And if you look at the the happiness scores, all the Nordic countries every year they they score very high on the happiness factor. So maybe maybe it's the natural way of living actually to to move within these seasonal changes and and adapt. I don't know. Maybe that there's something to
Kristen (27:04)
Yeah.
Paul Laursen (27:07)
Yes they do. Yep.
Kristen (27:08)
Yeah.
Yeah.
that that's interesting. Yeah. I mean, I think in the end at the end of the day, like if you feel good and you're not struggling with any sort of condition, proceed. You know, whatever you're doing, keep doing it. If you are a awake during the day, you can fall asleep when you want to fall asleep. If you feel like you have, the the ability to concentrate and focus and and attend to the people and things that you love in your life.
Just whatever you're doing, keep doing it. You know, ignore everything that anyone has to say. I, you know, it's it's I just think where I think where's why some of this research is happening is is because we're we're kind of in a unique scenario in modern times where we have access to light 24 seven, right? We have access to food twenty-four-seven and we just we just not ha we haven't adapted to
to to that 24-7 access, right? It it puts a lot of stress on our system. So I I will say, as it relates specifically to places like Finland and Alaska, and and really anywhere, even, you know, even in in Boston right now, I'm staying up a little bit later. I'm waking up a little bit earlier, than what I would in the winter. I really do try to just adapt with the seasons and and try to stay as aligned as possible to the extent that I can with work.
But but I think that is that's probably the best play.
Paul Warloski (28:46)
Kristen, you Marjaana had brought up earlier about, you know, races and the what we do before races. for races that start really early, what's the sleep strategy but the week before and when we travel to those races? How do we you know, what's the best way of dealing with that?
Kristen (29:03)
Yep.
I so I I've done a lot of work in this area. And I think the best strategy, obviously, you're not going to be able to move around like your race time, right? Or, you know, your tea time or whatever it might be. So in the lead up to those moments, the extent that you can, try to be as regular and consistent as possible. So everything that I've already, you know, that we've already kind of addressed, try to do that 80% of the time if you're really motivated 100% of the time. You can
kind of bank your resilience almost right to that perturbation that's gonna be happening in the lead up to race day. And I I see this unequivocally in the in the data. I I can say this with quite a lot of certainty that, if you are, 80 to 90%, dialed in on everything related to to sleep in the lead up to a race and your, you know, 48 hours of of disruption, like you should not see big,
Paul Laursen (29:41)
Mm-hmm.
Kristen (30:01)
performance decrements. Like you, you have banked a lot of the resilience and that is stored and and there for you. and I I really I think that that I can say that with some confidence. Yeah. Hopefully that's reassuring for folks. You know, it's but you do need to be strategic kind of leading into that endurance effort.
Paul Laursen (30:07)
Yeah.
Yeah.
Paul Warloski (30:14)
Yeah.
Paul Laursen (30:21)
Yeah.
Yeah, for sure. Just I'm just gonna go like I think there's a there's a context thing here as well. And and I don't know the answer to this, Kristen, but like again in my my daughter Kaya's performance I'm talking when I was saying her performance was off after some some bad sleep in in the morning and her performance in the morning, I'm I'm talking like point five of a second on a you know an explosive fifty fifty meters, right? And then we might that's that that's probably a little bit different.
Kristen (30:45)
Yeah.
Paul Laursen (30:49)
of of a performance than like a seventy point three or marathon kind of thing, right? Like there's different intensity levels where it's like, you go you kinda need that and so it's hard hard yeah hard to know, but that's yeah, these are where it could be some context that that that comes into play.
Kristen (30:54)
Yeah.
Yeah.
Yeah. I without a doubt.
Yeah. Yeah. And and I I guess I'm talking you know, I'm thinking about like military operators, who are kind of going into a mission set, for example, that might last forty eight hours, seventy two hours, you know, the the more kind of resilient they are going into that, the less perturbation we see in their resting physiology over the course of that seventy two hour block. So that's kind of what I'm drawing from and and I and I I I think that, you know
Paul Laursen (31:27)
Fully. Yeah, yeah, yeah.
Kristen (31:33)
And I think that kind of goes to Paul to your example in terms of like an endurance and MJ, you know, thinking about these in bigger endurance races. But but I but I think that, you know, point five seconds like that that matters, right? And these like when you're talking about a swim time and you've got one race, like the these differences actually then start to to probably matter. Yeah.
Paul Laursen (31:45)
Totally.
For sure. And J's
got a boy who's a top pitcher in in in sort of the minor minor league kind of thing and and he's yeah, again, this is that's where that's gonna matter for him too, right? It was like s something so explosive.
Kristen (31:58)
no.
Yeah. And I I you know, it's it's we we published a paper, I'm just gonna pull it up here. Yeah, wearable derived sleep and perform physiological metrics are associated with performance in professional golfers. And I I feel like did you have Greg Grysicki on? Okay, did he talk about this? Did he talk about the studies or did you talk about HRV digital?
Paul Laursen (32:19)
Yeah. Hey. Yeah, he was on the training science podcast. Not I don't
know, he was talking about the HR V C V and again that kind of almost comes back to your really comes back to your your consistency, right? Like y if just to close loop on that, if you if you're consistently falling asleep, you probably ha it's gonna help with your HR V C V, which is like the variation in your day to day HR V.
Kristen (32:28)
Okay.
I it you d Yeah.
Yep, exactly. No question it will help with training adaptation over time. And and that's really what we saw in this study with golfers. So this is basically the largest study ever done using continuous physiological data in professional sports. This is a study that spans seven years where we looked at roughly 300, I think it was 384 tour level golfers, professional golfers, and 590 tour events.
So we looked at and we looked at we had all of their physiological data, we had all of their performance data. So, you know, looking at their T to green and good shots, bad shots, you know, every metric you can you can imagine. And again, what we saw the more consistent sleep, the more in our actually our recovery, our proprietary recovery algorithm emerged in this study too, as being kind of predictive of golf performance. So
Paul Warloski (33:12)
That's awesome.
Kristen (33:37)
But but what was important about this study is that it's it's been such a long period of time, right? And we're looking at the same person over the course of this really long period of time. It's the consistency in their behaviors that mattered, that they were proactively managing recovery, not just a week or a month, but just it's a way of being in the world for for these these guys who are performing consistently. So it it's
Paul Laursen (33:50)
Yeah.
Kristen (34:04)
You know, in a sport like golf, to your point, you know, Paul, context really does matter. You know, all of these sports are going to be a little bit different. but when you look at golf where, you know, and swimming and, you know, where it's just like these, these, they're they're decided by, you know, tenths of a second, or, you know, they're decided by a half a shot, you know, and and there's so much online, like it's just like how you're behaving over the course of a a long stretch is really what matters. And and I think this idea that
These mini, these micro decisions that you're making, waking up consistently at the same time, viewing sunlight, they they freaking add up over time. They add up over time. And and to me, that's w you know, it's not glamorous and no one likes to hear it, but just being consistently good is is is I think the big story, certainly in that study.
Paul Laursen (34:42)
Mm-hmm.
Marjaana Rakai (34:57)
Okay, I'm gonna throw in another French. as as a mother, you know that when you have kids, your sleep is the first one to go. unless you have a live-inn nanny or something. So what what is your best advice for moms specifically or or dads who have little ones who take turns in waking up and then
Kristen (35:01)
Excellent.
Yeah.
Yeah.
Marjaana Rakai (35:23)
decide what they do or how much they do or how high intensity they do their training. Obviously what I'm hearing is that if you have a one bad sleep, that's not a big deal. But over time, you know, specifically if you have several little ones, you never know who's gonna wake up, right? So best advice for parents, please.
Paul Laursen (35:51)
Ha ha
Kristen (35:53)
Yeah, you're only as rested as your most rested child. Yeah, which is not rested at all. Yeah. totally, totally. I I love this question so much, MJ. And and I and I hope that I'm gonna be able to offer some reassurance and in some real tactical strategies for folks. because yes, I I live through this. I have, you know, I just a gazillion repetitions of folks who have the same question who write into whoop and are just desperate for for help and and not to mention shift workers who
Paul Laursen (35:58)
Yeah.
Marjaana Rakai (35:58)
Yeah yeah.
Kristen (36:20)
Essentially, parents are shift workers, right? They have the same kind of phenotype. So this is this is real stuff and and real pain that a lot of these folks feel. I think for parents, generally speaking, it is transient. You know, you're at six months, your child will start to have a more robust circadian rhythm. They will start to obviously sp spend longer in bed, their stomach size increases so they can hold more milk, they can stay satiated for longer, they're not waking up as much in the middle of the night.
So so it is transient, right? my kids were 18 months apart, so I kind of suffered, you know, for three-ish years, three and a half, where I felt like kind of pretty sleep deprived a lot of the time. but I I think what's important, so putting that kind of block of time aside for a second, what's important is when you get through that time frame, you need to get back on track. The most important thing for a parent is to not continue down that path where you are binging Netflix until one AM.
Right. And then having to wake up at 6 a.m. to go to your, you know, pee-wee hockey game. Right. So I I think it's it's so, so important that that parents get back on track. Because what what happens is you end up just adapting to a lower level of functioning, physically, mentally, emotionally, I would argue, spiritually. So, you know, I think once your your kids get through that patch of time, you get through that patch of time, you gotta get back on track. Okay. So that's I think the most important thing.
Paul Warloski (37:20)
Mm-hmm.
Kristen (37:48)
is to to to make that happen and and get the resources you need to make sure that that happens. I would say while you're in it, one of the and I and I I say this to athletes too and and this has worked so well. When you wake up and you you feel like you didn't have that great asleep. Technology aside, don't worry about you know quantifying it, but you know when you wake up, God, I just didn't feel super restful and you you feel like, gosh, I'm not like I just don't feel rested. Prior to to 12 p.m, if you can
Get in a 30-minute nap, a 20-minute nap, just where you literally like, you know, just like lie down, put a mask on, set your alarm, and just like do do engage in some slow paced breathing. Even if you don't fall asleep, just that slow paced breathing, that deactivation, it will help, you know, certainly if you are able to fall asleep. If you are really sleep-deprived, you probably will fall asleep and pretty quickly. that will you know, kind of block that.
Paul Laursen (38:23)
Yeah.
Kristen (38:45)
adenosine production, right? Like or not not block it, but it will kind of slow that curve down a little bit. So at 4 p.m. you're not like falling asleep, right? Like this will allow you to kind of make it through. So naps can be incredibly wonderful and strategic for new parents. And and I would say I think workplaces are becoming more aware and are starting to accommodate that. So I would really
I I think for folks who are listening who are like, I'm not sure, talk to HR. You know, see if you can get if you don't have an office, like, is there a place where you could just take a nap during the day? You know, like you're managing a young family. Like that is absolutely, I think we should be making accommodation for that in the same way that we make accommodation for a lot of other things. sleep really matters, you know, and as we all know, and and getting that rest that you need is not just a health.
Paul Laursen (39:34)
Mm-hmm.
Kristen (39:40)
thing, but it's a safety thing too. You're commuting. You are, you're taking your kids to the grocery store. You know, like when you are sleep deprived, you are less safe is just the reality of the situation. So I think advocating yourself for yourself in a workplace environment is absolutely critical. But I think naps are are huge. I think protecting your biological sleep to the extent that you can. So you know that first four hours is as good as it can be for until your child
Marjaana Rakai (39:50)
That's not a good
Kristen (40:10)
Does that maybe first wake up or the first two hours or first three hours? you know, making sure that you are capturing as much of that of that early stage sleep as as possible is really important. I think the other really tactical thing is when you do wake up, just making sure that there's that that it's there's dim light. So you can still safely move around. But again, light is that primary kind of photo.
Zeitgiver, that time giver that is going to tell your body whether it needs to be alert or asleep, right? So, if you're breastfeeding, for example, or your partner is, giving a bottle to the baby, just try to keep everything dim so you don't, you know, wake yourself up too much. Just want to be able to wake up enough to execute safely and then put the baby back to bed and then you lay down and just engage in your slow-paced breathing.
Paul Laursen (40:54)
Yeah.
Kristen (41:05)
you know, think the happiest thoughts possible. and I think that's really individual. You know, for me, I just kind of imagine myself walking through like this really pleasant meadow, perfect temperature, and I'm with someone I love and I slow pace breathe. And gosh, before I know it, it's like morning. So everyone needs to develop their own little strategy, but but that is a try to true strategy that does work for a lot of people. But engaging the breath first is the most important thing. Three, you know, deep breaths and then like just getting
Marjaana Rakai (41:08)
Mm.
Paul Laursen (41:21)
Yeah.
Paul Warloski (41:22)
Yeah. Yeah of
Kristen (41:34)
that slow pace through the nose, in through the nose, out through the nose, is a great technique. So I hopefully that's a few things for parents that I I think can really help.
Marjaana Rakai (41:44)
Amazing. Thank thank you. Don't do what I did when I did breastfeeding middle of the night. I I took my iPhone and scrolled. Don't do that.
Paul Laursen (41:44)
Yeah. I love it.
Paul Warloski (41:51)
Hmm.
Paul Laursen (41:51)
Ooh.
Try not to do that.
Kristen (41:53)
I know, I know. And and sometimes, you know, I think
I think phones get a really bad rap and and Michael Granziar, I have trouble pronouncing his name, but he's he's out of he's from Australia. he's done some really great work around this and it's the blue light from phones, if if you have that filter on, is not that it doesn't it doesn't it doesn't block melatonin from what I understand. it's more the content that matters.
If the content is engaging and kind of wakes you up or is upsetting, that is more of what impairs sleep onset than actually the blue light itself. So not that again, light really does matter. You don't want to be flooding yourself with big blue rich over lit over, you know, head light. but I think a little bit on the phone is not so bad if it passes the time. but as long as you can fall back asleep, I think that's the key, you know. So really again, as an individual evaluating what kind of works for you and what doesn't.
Marjaana Rakai (42:31)
Yeah.
Paul Laursen (42:46)
Mm-hmm.
Kristen (42:51)
and if if something works for you, ignore everyone. Just do what works for you. if you know, and and I think that that to me is the big the big takeaway.
Marjaana Rakai (43:02)
Yeah. Yes.
Paul Laursen (43:02)
Yeah. And I I guess almost
the the the other window we talk about a lot on the podcast sometimes, Kristen, is is the perimenopause and menopausal stage as well, which causes similar issues on this on the sleep. And I guess the your your advice is really similar. I I don't know if there's any extra context there, but it's probably probably almost the same.
Kristen (43:10)
Yeah.
Yeah.
It is it is really interesting. yeah, I would say some of the nuance there, you know, I think changes in hormones are obviously going to you know, progesterone, for example, when you have decreases in estrogen and pr progesterone, that impacts your anxiety levels during sleep. So a lot of those wake ups are due to the GABA receptors. so basically progesterone, I think
essentially is a is an anxiet anxiety reducer. and so when we have low levels of progesterone, we we f that whatever anxiety that is unresolved from the day is gonna build up and wake us up. So I I think that's really interesting. So I think there's, you know, a lot of the HRT or MRT can be potentially useful. that said, I'm a huge proponent for just these kind of circadian
Practices as a therapeutic intervention for all stages. But I have a paper in review right now looking at physiological heart rate, rhythm amplitude, and skim in skin temperature. So actually looking at the second to second rhythm of heart rate, second to second rhythm of skin temperature across the day in 5,000 women who are in perimenopause and menopause, in the individuals who have.
More robust rhythms, get this, have fewer menstrual and menopausal symptoms symptoms.
Paul Warloski (44:52)
Hmm.
Kristen (44:52)
So
you wanna preserve your rhythm. And it kind of goes back to my PhD thesis and that like I I just I you know this this idea that we we are in a modern world where we can operate
without actually having to engage the outdoors. And I and I think this really does come at a at a huge cost. And that's really what we see here. When with individuals who have this kind of lower amplitude, right, which is a combination of fitness level, just general robustness, right? you know, being able to have more regular sleep wake time, which is facilitated by more exposure to natural light.
You know, heart rate amplitude, there's a lot of things that go into it. But but the less robust this amplitude, the more you're going to suffer, is the bottom line of this research. And perimenopause, menopause, and we replicated it with men women who are menstrual naturally cycling. So preserving your amplitude, I think is a I is kind of like the next horizon. I think the next kind of natural therapeutic intervention.
and you can do this, you know, obviously, well, the other thing that we looked at. So I saw I I found these results, and then I'm like, my God, we need to look at like fitness levels. And and sure enough, independent of age, your amplitude predicts fitness levels. So we basically have a created a model. How many freak how frequently do you work out? What different, you know, kind of thresholds, like at, you know, are you working out high intensity, moderate, whatever, low, and then your heart rate variability, your heart rate, or your resting heart rate.
your exercise frequency, your BMI. and I think we put VO two moc max into that model. Okay, we're able to passively detect that. Both so we basically created a model for every single individual and basically amplitude predicted fitness independent of age.
Marjaana Rakai (46:55)
So when when you when you talk about amplitude, what w you're talking about the amplitude of changes in s heart rate throughout the s the twenty four hour and your skin temperature.
Kristen (47:05)
Mm-hmm. Yep. Circadian.
Yep. Circadian influence fluctuations in heart rate amplitude and skin temperature.
Marjaana Rakai (47:13)
Okay, okay, cool.
Paul Laursen (47:17)
So training. Training works, right? So are you saying training
Kristen (47:18)
What's up? What's that?
Paul Laursen (47:21)
works?
Kristen (47:23)
training's the thing. And and I would say for our parents who are struggling, you know, doing a couple sessions of high intensity, we see that that's actually protective in shift work. I I haven't been able to publish these data yet. This is from a Stanford medical data set I had with surgeons, but but one of the the the more people worked out, the fitter they were, the less impacted they were by shift work, both ph objectively object objective markers and subjective markers. So
Absolutely. Fitness can, you know, could help with a lot. But yes, we just get a set for sure.
Paul Warloski (47:50)
Yeah.
Marjaana Rakai (47:54)
Yeah, so so for perimenopausal
women, I can't remember the the author's name, but I it's somewhere from Europe. they show that exercising during perimenopausal changes helps with the symptoms. So you're not seeing all those symptoms that you would if you didn't exercise. So essentially women cannot care. Yeah.
Kristen (48:17)
Probably cited that paper. Yeah. A
hundred percent. I you know, and it it's hard to, you know, I I think people don't like to hear that necessarily. but but we know, you know, HRT, MRT at has it's not, it's not a panacea. You know, hormone replacement therapy is not the panacea. Like if you are not taking care of the big rocks, nutrition and exercise primarily and sleep, you know, you're probably still gonna suffer, right? And that is exactly what we see in these data. The more robust you are, the fitter you are.
Marjaana Rakai (48:33)
Okay.
Kristen (48:47)
Just literally the less you suffer. And and and if I don't know that is if if if that isn't a call to action for folks, I don't know what is, but that's the thing to prioritize. It's just like is just get as fit as you can. you know, you know, inside the constraints that you're faced with. But but yeah, that's the that's the path.
Paul Warloski (48:53)
Mm-hmm.
Marjaana Rakai (48:59)
Yes.
Paul Laursen (49:06)
Amazing. I I mean that's that's what we're all about on the on the Athlete Compass podcast and and with Athletica. So we're trying to make people more robust. Sounds like I mean your your data set that you have at Woop Kristen is just phenomenal. Like it's so paying off now, right? In terms of the insight that it brings, the studies you can do. I I mean, god it's incredible.
Marjaana Rakai (49:06)
I love it.
Paul Warloski (49:08)
Yeah.
Kristen (49:10)
A whole
Paul Warloski (49:11)
Mm-hmm.
Kristen (49:22)
I don't know.
I thank you so much for saying that, Paul. I, you know, it's been such a grind, you know, these last like 10 years just putting this puzzle together. But I do feel like the puzzle is is starting to come together in ways that are really exciting. And most importantly, I I think a lot of what what we're finding is that many of these behaviors are just are indeed accessible, right? To a vast majority of folks. We're not talking about these crew.
Paul Laursen (49:33)
Mm-hmm. Yeah.
Kristen (49:53)
crazy protocols, right? Like it's just like a lot of the simple stuff that you all advocate for. You know, it's getting your high intensity training and getting your moderate levels of activity and, you know, the resistance training. Like that's really like the place to start and the thing to invest in first.
Paul Laursen (50:07)
Yeah, absolutely. So just yeah
Kristen (50:09)
We see the people the
more people work out, the fitter they are, actually the less time in bed they have to spend to achieve like the same sleep, like the same kind of I don't know what to call it, but sleep in the integrity of of their sleep. the fitter Yeah, the the fitter you are, like the and we have this paper's in review too right now. You know, not surprising, but but I think again, fitness, fitness, fitness.
Paul Laursen (50:15)
Yeah. Yeah.
Robustness, yeah.
Yeah, yeah. Well you make y I mean fitness and training is one of the key things that you know just facilitates the ease of going to sleep and staying asleep, right? It's like you're so that that's a it's yeah, like you and you mentioned that as one of your four pillars, right? The zone two training, but really you know, just a a regular hit of training consistently is is one of those things that's gonna help with the the sleep consistency and and staying asleep and going to sleep faster and all that. Yeah.
Kristen (51:05)
All of that.
Yep. And there was a Yeah.
Paul Laursen (51:07)
So huge, huge
huge yeah, just huge shout out to to to Woop. We we Woop Woop data comes in to the Athletica platform via intervals.icu integration. So if you're a if you're a Whoop user, which I hope you are, you get that you get that data connected into your intervals.icu and then link that through to your Athletica and it will appear on your recovery profile.
Which of course is uses the methods of Dan Plews Marco Altini, colleagues of Kristen. So it's it basically it's the exact PhD of those guys embedded within the Athletica algorithms that our AI coach will use to interpret and and give you insight in the context of your entire training. So yeah, it's it's it's a fascinating world that we're in, Kristen, and and we're really grateful for all the work that you and and your immense team at Whoop do.
Kristen (51:56)
So good.
Paul Laursen (52:04)
to to help bring that that data and insight that's that continues to come to to our platform as well. So thank you and and the team.
Paul Warloski (52:13)
Thank you for listening today to the Athletes Compass Podcast. Take a moment now, subscribe, share, and let's keep navigating this endurance adventure together. Improve your training with the science-based training platform Athletica and join the conversation at the Athletica Forum. For Dr. Kristen Holmes, Marjaana Rakai, and Dr. Paul Laursen I'm Paul Warloski and this has been the Athletes Compass Podcast. Thank you so much for listening.