WHOOP Podcast - The Relationship Between Exercise, Sleep, & Recovery with Josh Leota

Episode Date: July 23, 2025

We know sleep and physical activity are crucial for overall health, but how do they affect one another? On today’s episode of the WHOOP Podcast, WHOOP SVP of Research Algorithms and Data, Emily Capodilupo sits down with Sleep and Circadian Scientist Josh Leota to break down the latest WHOOP study on how intense exercise and timing affect sleep—and how sleep, in turn, influences your ability to train. Josh shares his insights on two major peer-reviewed studies, using WHOOP to analyze data on sleep and physical activity. The results? The closer to bedtime you train, the more your sleep is affected. Whether you're an early bird, night owl, or somewhere in between, Emily and Josh offer science-backed strategies to optimize both sleep and physical performance without sacrificing either.(00:33) Using WHOOP For Data Collection In Research Studies(02:43) The Study: High Intensity Training’s Effects on Circadian Rhythm(05:05) WHOOP Podcast Rapid Fire Questions(06:06) Do Late Night Workouts Affect Sleep Quality?(10:44) The Hawthorne Effect: What Is It and Why Is It Important?(12:57) How Do Sleep Patterns Predict Next Day Performance? (17:32) What Happens To Exercise When Sleep Cycles Are Disrupted?(23:47) Early Birds vs Night Owls: Why When You Train Matters(30:21) How To Optimize Sleep and Exercise as a Busy Individual(33:26) Advice & Practical Takeaways From The Study(42:59)  What’s Next? Foreshadowing Future WHOOP StudiesSupport the showFollow WHOOP: www.whoop.com Trial WHOOP for Free Instagram TikTok YouTube X Facebook LinkedIn Follow Will Ahmed: Instagram X LinkedIn Follow Kristen Holmes: Instagram LinkedIn Follow Emily Capodilupo: LinkedIn

The cool thing about our study is we managed to look at the product of intensity and duration, which we call exercise strain, and which whoop does a great job of measuring. We found that as strain increases and as your exercise finishes closer and closer to when you typically go to sleep, we find that your disruption to sleep and heart rate during sleep get progressively worse. So two really interesting and clear what we call dose response relationships between the timing of exercise and sleep. and also the strain of exercise. Hi, everybody. I am Emily Capitalupo,

Loup, Senior Vice President of Research Algorithms and Data. And today I am joined by the incredible Josh Leota all the way here from Melbourne, Australia. Thank you. Thanks for having me. It's great to be here. We are so excited to have you. Josh has his PhD from Monash University where he's part of the Sleep and Circadian Biology Research Program.

And we've been working together for almost four years now. Yeah, yeah, close to it. Recently, we've had two papers published that came out of that research collaboration. We're going to talk about both of them in this podcast. So we are so, so honored that you flew halfway around the world to be here with us today and talk about these really great papers. Yeah, great. I'm excited.

So why don't we start off? How did we start working together? What was this project we've been working on for the last four years? You're right. About four years ago, I was just starting my PhD, and I was working with elite athletes looking at sleep and performance. And I was struggling to find the right tools to record and to monitor sleep with athletes.

It's a tricky population to work with because they're so focused on their performance. And the current methods and techniques that we were using weren't quite up to scratch. So I was looking at what was at on the market and I came across whoop. And the thing that drew me to whoop was how non-invasive it was. and the quality of data was just incredible and something that we didn't have access to at the time. So at that point, I reached out to you and told you some of my crazy ideas. And since then, we've been working together on a few different projects. And it's been amazing. Yeah. And it was kind of like a lucky connection because we'd been working with other people in your same research

group at Monash University on this project called the COVID Resilience Project. You can link some of the papers that came out of that in the show notes. So I knew some of the people that you worked with. So when I got the cold email, because we do get too many of those to answer every week, I was like, ooh, we like Monash. These guys are awesome. And so it was sort of easy to say yes to that one. And I'm glad we did. So what was the project? So we've been interested in how exercise in the evening is associated with changes in sleep. And the interesting thing about this area is I think a lot of people intuitively know that working out really late at night has these effects on how we sleep. And working with athletes, there are number one complaint has always been following a

night game or a night competition, they really struggle to fall asleep. They struggle to stay asleep. And when we look at the literature, there were two recent systematic reviews and meta analyses in this area. And they both concluded that exercise in the evening has no effect on sleep. And I was pretty blown away by this. It went against my own personal experiences and our experience working with athletes. So we dug a little bit deeper. We had a look at every study that was reported in these reviews. And the majority of the exercises that were prescribed in the studies were very light exercises, so 20 to 30 minutes on a cycling bike at moderate intensity. So we thought maybe it's all to do with how physiologically demanding

the exercises. And Woop has this incredible data set where you can track your strain in your exercise. You can also track when you exercise and when you finish that exercise and how that's associated with sleep. So that was really the beginning of the project. Yeah. So I think there's a funny moment where intuitively it seems obvious that, you know, if you're thinking, oh, I'm going to go to bed in the next hour, like I think we all generally know, like the thing to do is not go for a really hard run. And so I think there was common sense around exercise in the evening being bad for sleep. Also all this data from athletes that I think because it was associated with nighttime games was getting dismissed as, oh, you're just amped up from the game or something, even though

the exercise itself kind of fits with logic and intuition. And then these two like great papers are seemingly, you know, good research methodology, all that kind of stuff in prominent journals are coming out and saying, nah, it doesn't matter. And so you came to me with this idea of, you know, let's do the definitive study. Let's answer this question once and for all. And so before we dive even further, we're going to do something a little bit fun. I'm going to rapid fire some questions to you. And you get to answer just true or false. And if that's really painfully hard, well, one sentence answer if you feel like you need to. Okay. So true or false. Intense workouts performed within two hours of bedtime, delay your sleep and shorten its duration.

That is true. All right, true or false. Can low strain evening workouts still negatively affect your sleep if done close to bedtime? Yes, but very close to bedtime. Okay, we'll dive into that nuance soon. True or false, a high strain evening workout can raise your resting heart rate by up to nine beats per minute. That's true. All right, two more.

True or false. Does bright light exposure during late night training sessions impact your circadian rhythm and sleep onset? True. Yes, true. And then last one, true or false. Training hard at night improves recovery because it helps you fall asleep faster. I would say false. All right.

Well, we're going to dive into the reasons behind all these answers as we go deeper into the study. Okay, so going back to our study. So we set out with this lofty goal, definitively answer this question of, you know, are all these athletes and are all of these kind of normal intuition around exercise correct? Or are these two kind of prominent meta-analyses correct? What did we find? What surprised you? That's a great way to ask the question because I think we found that both were correct. Because one thing about the studies that it performed in the past were, like I said,

involved a lot of low strain exercise. And a lot of them could only really manipulate either the duration of exercise or the intensity of exercise. So the problem with that is you can have a short duration, high intensity exercise that will put a lot less. strain on the body than a long-duration, high-intensity exercise, but they're essentially treated as the same thing. So the cool thing about our study is we managed to look at the product of intensity and duration, which we call exercise strain, and which WOOP does a great job of measuring. So we found that as strain increases and as your exercise finishes is closer and closer to when you typically go to sleep, we find that your disruption to sleep

and heart rate during sleep get progressively worse. So two really interesting and clear what we call dose response relationships between the timing of exercise and sleep and also the strain of exercise and sleep. You know, what I love about your answer and sort of about the study in general is like there was this like false premise of a question. that was being posed, right? Like is one side right or the other camp, right? And I think there's this such a tendency in science and in making everything tweetable that it's like one camp wants to say exercise at night is bad. The other camp wants to say it's fine. And, you know, with all things science, the answer is like almost always it depends. And what's cool that our study

is it depends on a few different things. It depends on the intensity. You know, you talked about duration and then sort of the relative timing to how close to sleep you actually get. And one of the things that I think you and I talked about four years ago when we were teeing this up is that a lot of the studies that have attempted to answer part of these questions and then do like a polysumography in a lab. Those take like a half hour to set up. And if you're trying to set up a whole bunch of people, it's like they were never even getting within like that last hour of sleep because there were so much like set up and stuff that had to happen that like you just practically speaking you couldn't make the protocols work and so like one of the huge advantages of our study is that

you know it was free living conditions passive you know monitoring via wearable and we were able to pull in over four million nights of data where somebody had an evening workout followed by a sleep and so we were able to power the study across all these different variables and slice and dice the data in a way that, like, you know, just hadn't been done before and, like, more traditional in lab setups. And so finally answer some of these questions and tease apart some of that nuance. Yeah, exactly. And the other thing about these lab studies is it's such a foreign environment for people to sleep. Not only does it take, like you said, 30 minutes to set up. I don't know if you've ever slept in a sleep lab. I have. I donate my body to

whoop science all the time. Well, I'm sure your mattresses are much more comfortable than the typical sleep life, but it's very difficult to sleep in foreign conditions and environments. And, yeah, the beautiful thing about the whip device is the participants in the study, they're in their free living conditions where they're going about their everyday life as they would any other day. So there is no hawthorn effect where you know you're being monitored and you're expecting. thing that your behavior should act in a certain way. It's as close to the real thing as we can

get. What's up, folks, if you are enjoying this podcast or if you care about health, performance, fitness, you may really enjoy getting a whoop. That's right. You can check out whoop at whoop.com. It measures everything around sleep, recovery, strain, and you can now sign up for free for 30 days. So you'll literally get the high performance wearable. in the mail for free. You get to try it for 30 days, see whether you want to be a member. And that is just at whoop.com. Back to the guests. Can you talk a little bit more about that for people who aren't familiar with the Hawthorne effect and why the free living element's important here? Of course. So I think that particularly

relates to the PNAS paper. Yes, yes. Well, the Hawthorne effect, there are a few different ways that it can come about but essentially when you know you're a participant in a study and even when you start to get an inkling of what the research is trying to get out or what the researchers are hoping that you do you can start to consciously or otherwise change your behavior to hopefully give the study the results that it's looking for and I think this is such a funny phenomenon that speaks to like this deeply social thing with humans like even if you know you're supposed to be like acting normally. Like we so badly want to like please people or like participate or go with the flow or whatever that you get these really funny things. And then of course, having slept in a

sleep lab a couple of times, you know, when you're not in your room and, you know, somebody's watching you, you just take away one distractions. You know, my dog wasn't in the bed. My husband's not in the bed. Like you can't just do one more load of laundry, right? Like any of those things. I'm stuck in what's basically like a really boring hotel room working thing. and I have no choice but to sleep. And, you know, you get all these funny things. Like, I don't want to be judged for scrolling my phone or something, so I might just sleep. And so even if it's not coming from a, like, there's just something very unnatural about, like, being monitored.

And that doesn't even start to account for all the things of you've got, what is it, like 30-something wires on you when you're doing a polysomography. You've got stuff in your hair. You've got stuff all over your body. So, you know, any observed effect that, like, oh, you've slept poorly after I. exercise. It's like, no, I slept poorly because I was like hooked up to all these very unusual light. Exactly. And I think the purpose of research is to uncover things that can be generalized across, not just different people, but people's lives going forward. So you really want to get the conditions of your study as close to what it looks like in the real world as you

can. Yeah, which has been, I think, one of the really powerful things about all the research we do here at Loop and something that definitely applied for these papers. So we talked a little bit about the first paper that came out in April in Nature Communications, and we will link that in the show notes. And but we haven't talked yet about the second paper. So in our first paper, we looked at the relationship between evening exercise and the subsequent sleep. What did we look at in the second paper that recently came out in PNAS? So in the second paper, we kind of flipped the script, and we asked the question, how do sleep patterns the night before predict exercise the following day? And the cool thing about this paper is that went through a number of different versions and iterations.

And the final product that we ended on, the final paper, is great. But going through all of these iterations, we're able to see the data from like many, many different ways. And that was really cool. So what we did is we looked at how someone sleeps on average. And then also how changes in their sleep from their average were associated with exercise the next day. So we looked at what we call between and within person associations or average and daily changes in sleep. Do you want to get into what we found? Yeah, and I think just to frame it a little bit more, we had over 5 million nights of data in the study.

And the people who were included in the study, we pulled a full year of their WOOP data. So September 2021 through September of 2022. Yes, and we had almost 20,000. Yeah, so it was a lot of people longitudinally. And so we were able to look at when you said like within and between people, how people's sleep changed on nights before and after exercising. And so I think one of the things that was cool because we use basically the same data set or subsets of the same data set for both of these two papers is in the first one we were looking at how exercise affects sleep. Then we started looking at how sleep affects exercise and ordinarily studies like this are so noisy because there's so much variation in the exercise that people choose to do, so much variation. variation in sleep habits within and across people because of all the things like work pressure

and whether or not your kid wakes you up and if you're at home and et cetera, et cetera. But when you start to have hundreds of data points per person across tens of thousands of people, across, you know, total of millions and nights of data, all of a sudden things, the signal pops out of the noise and you can see things that just wouldn't be powered in these smaller studies. So with that framing, what did we think? Let's start with the between-person effects, so at the average level. When we look at sleep duration, we actually found that those who sleep for shorter durations on average actually exercised more.

So the average of the sample was about seven hours of sleep, which is actually pretty normal and pretty close to the general population. But for those who slept five hours on average, actually exercised 20% more on average. Whereas those who are long sleepers and sleep nine hours on average, we're actually exercising 20% or less on average. So a really interesting finding and is consistent with what a lot of previous research have found and that longer sleepers do exercise a little bit less. And there are many different reasons for that. When we looked at average sleep onset timing, so when they typically go to sleep at night, we found that earlier types exercise. a lot more. So the average sleep onset was about 11.15 p.m. And for those who went to sleep at

about 9 p.m., they were actually exercising 43% more often and for longer than those who had a very late sets of the late types who go to sleep on average at 1 a.m. So big differences. And I think that that is all due to the way that society sets up the 9 to 5 working day. It's much more aligned for early types because they have the opportunity to exercise in the morning. Then they can go to work and go about their day. Whereas if you're a late type, you're going to sleep at 1 a.m. You're getting up just before work. It can be a real struggle to catch up.

Again, very consistent with what previous research has found. So that was cool. And I guess what makes our study a little bit different is we then looked at the within person effects. So how does changes in an individual sleep relative to their own? average, predict how they're going to exercise the next day. And I think what we found was really cool because it's a little bit more complicated than just sleeping less or sleeping more is good. So when people went to sleep a little bit earlier or when they slept a little bit less, they were actually more likely to exercise the next day and they exercised for longer

periods of time. However, extreme sleep loss. So when people got four hours or three hours less than they typically sleep. We actually saw the opposite effect. They were exercising less. Whereas any extension in sleep, so any increase in your typical sleep duration and any delay in your sleep onset, so going to sleep later than you typically do,

was associated with these stark reductions in next day exercise. So there are a few things going on that I think are really interesting and we could talk about. But firstly, this idea that small changes in sleep with respect to slightly shorter sleep and earlier sleep, I think is a great sign that people are, I guess, modifying their sleep and sacrificing a little bit of sleep to make way

for exercise the next day because our lives are so busy. We've only got 24 hours in a day. Sometimes you really have to move things around to fit exercise in. Yeah, and I think there's such an interesting point to kind of really make sure that people understand here, which is that like, you know, you talked about the sort of immovable block of like the nine to five workday plus pad that with commuting time. Plus, you know, a lot of people come home and, you know, they need to eat dinner right away because either they're hungry or family and they're trying to do that. And so there's this big like chunk right in the middle that's not super flexible. And then sort of all the rest of the time that's not kind of already spoken for,

this big and movable block is about trade-offs. And so we see that, like, the people who are exercising more are sacrificing sleep. And I think one of the things that's so beautiful about that finding and so interesting to think about is that, like, we often give people this message of, like, you have to exercise and you have to sleep and just figure it out. But the reality is, and we see it play out in, like, free living data is, like, you actually have to kind of figure out how to balance those a little bit because it's often one at the expense of the other. Yes. It often is, but it doesn't have to be, which is the really cool

thing. And I think this is a great study to show that adjusting or making work hours a bit more flexible could really benefit population health. So the American Heart Out Association recommends between 150 to 300 minutes of exercise per a week. And one in five Americans managed to fulfill that recommendation. So four out of five Americans are insufficiently active. So we really have a big problem. We need to get people moving because broadly speaking it's the number one thing you can do for a long-term physical and mental health.

And I think one way that we could do this based on these data are to make our work scheduling a bit more flexible to account for time to exercise. The other cool thing is that we look at, at what combination of sleep duration and sleep timing was associated with the optimal level of exercise the next day. This was really cool. And we found that it was in fact when people got their normal sleep duration, but we're going to sleep one to two hours earlier, which is a really cool finding because we don't want to be recommending that people sleep less so that

they can exercise. But this shows that we can go to sleep a little bit earlier and protect our sleep duration. We can still get the sleep that we need. And that allows us to wake up a little bit earlier and then get that exercise in either before work or at some stage in the day. And it does show that we can have both sleep health and physical activity health kind of coexist as one. Yeah, and I think this is where the two papers tie in really beautifully because you're saying, Like, if we go to bed earlier in order to accommodate working out in the morning before work, that that's better associated with achieving this American Heart Association target. Like 150 minutes per week is about like 21 and a half-ish minutes per day. It's really attainable.

So we're not talking about going to bed, you know, at 5 p.m. or something that's just like so wildly unreasonable. It's, you know, something like, you know, how can we make just 22 minutes in the morning for this? And then, you know, when people kind of plan to work out in the evening because they're evening types and that, you know, might feel like more of a natural inclination, you see more of that trade off to next day sleep quality. And so it might feel like, oh, like this is how I'm choosing to get my 150 minutes in. But because of the way you trade off on sleep quality and that reduced sleep quality reduces my next day propensity to work out, it's actually long term a worse strategy. Exactly. And like you said, those 25 to 45 minutes per day, they can come at any stage in the day. They don't have to be within one block. And that's one real strength of this study is we looked at physical activity, which we call exercise, but it's moderate to vigorous physical activity across the entire day. So from the moment that you wake up until the moment that you fall asleep, even if it's just two minutes of doing star jumps or quickly smashing out 20 push-ups or something like this, that's all calculated within this study. So trying to squeeze it in whenever you can. And if that means going to sleep a little bit earlier, then I think this could have a real benefit to the

population. You're invited to join the wait list for WOOP Advanced Labs. Advanced Labs delivers clinician reviewed lab results right into your WOOP app for the most complete view of your biomarkers and biometrics and the most comprehensive understanding of your health. Unlike other test, WOOP integrates your lab results with your WOOP data. See how your habits and behaviors influence your biomarkers and get clear guidance on what to change to improve your results. To join the wait list, visit our website or the health tab in the WOOP app. So for the PNAS paper, we looked at two different groups of people, those who are sort of naturally inclined towards earlier bedtimes, earlier wake times, and then those who were more naturally inclined

towards the later bedtimes, later wake times. It seems like easy from the sort of data analysis perspective to go like, ah, more people should just like adopt sort of the morning pattern. It's better for you. It's more associated with kind of meeting these American Heart Association guidelines, et cetera. Is it really that simple? Like can I just choose to go to bed earlier and, you know, expect all of these like improved exercise habits to follow or are these like fundamentally different people where the later kind of kind of. night owl types are just disadvantaged with this mismatch to the typical work schedule. I definitely don't think it's as easy as just going to sleep earlier.

You know, these are definitely different types of people all the way down to their genes. Some people are just more morning types and some people are more late types. And when you fight against your own circadian biology and try to change your scheduling too much, it can make life really tough. So I wouldn't recommend that if you feel like you're a late type and you struggle to fall asleep early to try and force your way and to becoming an early type by waking up early and seeing if that helps, it likely won't, or at least it won't be sustainable. And I think the main reason we see such vast differences in exercise patterns between late types and morning types is to do with environmental constraints around, like you said, the way that the... modern day is set up. It's much more in favor of morning types. So I guess doing your best to find time to exercise, which is easier set than done. Our circadian rhythms, they are very flexible and

we can handle small changes in our sleep wake timing, particularly if you're getting light early enough. You can shift your circadian phase a little bit earlier. But there isn't great evidence for shifting it from 1 a.m. all the way to 9 a.m. in hopes that'll help you exercise more. And we don't even know if that's going to be the case. So I would say continue listening to your body as best you can, but try and prioritize both sleep and exercise during your day-to-day activities. So this is a little bit outside of the scope of our paper, but I think is an interesting question that kind of comes up in response to some of the findings, which is this finding that the people who are exercising more are sleeping a little bit less. On the extremes, like the people who

are sleeping nine plus hours, I think this is like a fairly well-documented phenomenon, right? That's a behavior of people who are chronically ill. You know, people who are battling depression tend to sleep for a really long time. And so I think like it makes sense on that extreme, you know, when you're talking about nine, ten plus hours, that that would be associated with less exercise and is probably confounded by a lot of other comorbidities and things. But in this kind of difference between, you know, six, seven, eight hours, all of which we generally think of as sleep patterns of healthy people, exercisers are sleeping less. To what extent do we think that's people making the conscious decision to trade exercise

for sleep? So they're saying, like, you know, I would love to sleep another half hour, but I'd rather be 90% sleep score if we're talking about whoop and get my workout in versus. is 100% sleep score and not hit my strain target? Or is it the case that athletes need less sleep and therefore it's more comfortable for them to forego that sleep because they're actually more rested after six, six and a half hours? Yeah. So I think it's more of the former in that just to fit exercise in, you're going to have to sacrifice something somewhere. And a lot of Weep users are extremely physically active.

So sometimes their workouts are, you know, a couple of hours, almost every day. And that has to come at the expense of some other behavior. And likely it could be sleep. Now, I don't know if they would wish that they could sleep more. I would guess that maybe they would. And periods of my life where I trained a lot, I was wishing that I had more time to exercise. And that's just, I think, a consequence of the modern world where we're so busy with, work and we want to also fit in our exercise goals and fit in our social goals. Sometimes

something's got to give. What we did find, though, is that once we got to about five and a half hours, anything below that, there was no significant difference. And one of the reasons is that there are so few people at that extreme that the confidence intervals get really, really large and we don't see any either increase or decrease at that point. And with your second point about athletes needing potentially less sleep. I think the data actually show the opposite, which is interesting. When you look at elite athlete populations and studies that have looked at how much strain that they achieve during the day, you actually see an increase in sleep need that following day. And also the next day sometimes you can have this kind of carryover, which makes

a lot of sense. You also see that they nap more. And when you put your body through physiological stress, you need to replenish it somehow. And that comes from nutrition, but it can also come from sleep. So I don't think that it's that these elite athletes on the WOOP platform are just these superhuman aliens who don't need sleep. Everybody needs sleep. And particularly those who are putting their bodies through a lot of stress need even more sleep. Well, I'm feeling very validated by your answer because the WOOP sleep need algorithm does increase your sleep need as a function of your strain. And we get pushed back from people sometimes on that, mostly members. But, you know, our read of the science is definitely that this is supported. But it's interesting when you see this data

that seems to show, no, look at all these athletes performing at this high level, getting less sleep. That must mean that they need less sleep. And I think that's one of those common like fallacies of research where it's not that they need less sleep. It's that they're willing to make a tradeoff and prioritize this. And so I want to kind of as we get close to. to wrapping up here, try and wrap some of these findings into practical takeaways for people. So if my life is full of constraints, busy job, busy mother, whatever, and I can't magically poof an extra two hours into my day, how should I think about optimizing that sleep versus exercise trade? And like, if you just kind of want to monologue for a moment,

moment, like top five things across the two papers you'd want people to be taking away. Sure, sure. Yeah. It's a great example of a busy mom. I must have come from somewhere close by. But anyway, I think the thing to remember is that both of these behaviors, sleep and exercise, are extremely important for your long-term health. And our bodies are very robust and well equipped to deal with small disruptions to either, but are less so when it comes to longer chronic changes in both exercise and sleep. So if you feel like the only time you've got to exercise is at night, we would never want to discourage exercise, and in particular, strenuous exercise has so many amazing health benefits. One night of exercise followed by small disruptions

to sleep should be okay to handle, but when this becomes a pattern and a habit of only exercising at night and feeling like you're jeopardizing your sleep, then we would try to recommend maybe moving a few things around. And the other thing is if the only time you have to exercise is at night, particularly within four hours of when you go to sleep, try and keep that exercise as light as possible. We found that as a rule of thumb, the harder you work out, the longer you need to recover before your body comes back down to baseline can facilitate sleep, both the initiation of sleep, but then also being able to stay asleep across the whole night. So keep that in mind when you are exercising at night, try to opt for those

lighter strain exercises. I think one of the things that was so beautifully illustrated in the figures in the nature paper was that as you get like really into that last hour before bed, The slope changes pretty dramatically, and that's just, like, almost at any strain level, awful for sleep. So I think, like, it's easy to kind of sit here and be like, don't work out four hours before bed. I think, like, to those people who are, like, craving nuance, it's, like, really try not to exercise in the last hour before bed. Know that in, like, four hours to bed through, like, one hour before bed, as you get closer to that one hour mark. And as the strain goes up, it's more and more disruptive to your sleep. So that's the stuff that you're going to want to start to think about, like, okay, I like for whatever

reason, I'm very compelled to work out now. You know, if I can keep it lighter, if I can keep it as early as I possibly can, it'll be better. I think like an interesting, if somebody wanted to pick at the question, it's like, if it's nine o'clock at night and I'm like, I really want to go lift, right? And my plan was to go to bed at, say, 11. It's not the case that it's like, I should go to bed at 12 instead. Let's say I'm going to lift from like 9 to 10, right? Because whatever worst quality that hour from 11 to 12 is going to be, it's still better than nothing. So kind of with some of those like practical things in mind, like what would you tell people the paper sort of says, like, this is what you shouldn't do, this is what you should like. This is what you should

like try and plan to not do. But if you find yourself in this moment, sort of what are your options? Exactly. So if you are looking to engage in that really strenuous all-out exercise, we would recommend trying to do that earlier in the day or at least finish it before, four hours before you typically go to sleep. And then if your workouts do creep into that four-hour window, try and keep it lighter and as you get closer and closer to bedtime, you know, dial it down even more. But like you said, if you do find that you're finishing one hour from when you want to go to sleep, don't delay your sleep onset. See if you can, you know, bring your heart rate down, have a warm shower, go about your typical nightly routine. Get in bed and see if you can

fall asleep because if you can, great, you may notice some slight disruptions throughout the night, but sticking to that sleep routine is going to be so much better than worrying about, oh, no, I've just exercised. I'm not going to be able to fall asleep for four hours and staying there. Right. Don't like wait the four hours because that's some kind of magical window. Exactly. Yeah. The first marathon I ever ran was Las Vegas, which happens at night. So they do it like it's at sunset. It's on the strip. It's super fun. Highly recommend. But you finish like 9.30 at night or kind of pretty big window, people who are faster than me finish earlier. And I remember like kind of being done and then getting like room service pizza and, you know,

having like amazing sleep. So, you know, I think like some of these things are are complicated because, you know, if you put this incredible load on your body, like you will fall asleep. And so we're definitely not saying like stay up four hours or anything like that. Yeah. And then if you if you look closely at some of the figures, you'll see that for maximal exercise strain that happens during the day, you actually see an increase in sleep duration, which is really cool. And that's an increase from the days that they don't exercise at all. So like you said, you run a marathon, you need to replenish your pizza and then you need to recover. And your sleep, your sleep need is through the roof, right? So it's not surprising that you had a great sleep at night.

Yeah, but I think sort of the practical advice is to the extent that you can plan ahead, plan to do it earlier. If you're choosing between like, should I stay up late tonight to work out or should I just go to bed and wake up earlier tomorrow morning to work out, the latter is highly preferable. But if your circadian sort of phase preference doesn't allow for that, it's not horribly damaging to work out at night? Or what would you tell people who are like, that's the only time I can work out. It's when I love to work out. Your paper annoyed me. I did get some of that back. That's true.

And I would say, just know that our paper was looking at when we say evening exercise, we're not talking about a specific time of the social clock, as in like 9 o'clock, 10 o'clock, whatever. We're talking about the evening relative to your own sleep and weight patterns. So if you don't go to sleep until 1, 2 a.m., we're actually talking about the 4 hours before that period, whereas if you go to sleep a lot earlier, your evening is going to be. earlier. So we're not attacking evening exercise. It really does depend on each individual, which I think is a really important takeaway from this research. We tried to personalize all of the analyses so that we're always looking at strain relative to someone's capacity to handle

strain, sleep relative to when they typically go to sleep. Sleep duration and timing compared to their average. We really try to take this personalized, individualized approach and just know that there is huge heterogeneity in how people deal with these types of exposures. So you may find that you can handle evening exercise. You may find that it's a lot more challenging. There's big individual differences that you should be aware of. So just because a study as a whole, looking at averages, finds a certain result. Don't think that you're beholden to that result because, or that we're saying that is

relevant to you. It could be that your specific circadian zoology is a little bit different. And I love that point because I think that that's very whoop and that like, you know, we did the study on 20,000 people and the odds are that whoever's listening isn't in that group. And so, you know, you can put these great papers together and sort of say, even in a study like this where we had, you know, it was people from around the world, a really wide representation. of age groups and I think was it 92 different types of exercise that people did. So a really wide-ranging study, part of what Woop lets you do is we'll say, here's the general science as we understand it, but go experiment, go see what happens. If you feel like you love working out

at night because, you know, you're finishing your day and you still have a lot of energy and you want to burn it off, you know, you can do these N of 1 studies and we'll show you what happens to your recovery score. We'll show you what happens to your sleep and it'll be pretty clear. after a couple of workouts or a couple of evening workouts, if, you know, you're very sensitive to this and should really work hard to change this pattern or if, you know, you're reasonably robust to it and can handle it. And I think, you know, and I think this is also where some of the tweets and things that I've seen about, especially the nature paper, sometimes oversimplify things where it's like, science says not to work out at night. You know, I think an important takeaway for

people is like it is generally preferable and the data suggests more sustainable to work out in the morning. But a massive body of literature has shown that like exercising is better than not exercising. And I think like people should to a certain extent sort of give themselves permission to fit in those 22 minutes a day or you know 20 to 45 minutes a day in whatever way is going to work for them. Yeah, that's beautifully put. What other findings, a practical takeaways do you want to leave our audience with? What you were talking about just then was beautiful because you should go and experiment. And one thing that I would love to look at in the future is whether there are certain recovery activities and processes that may help minimize the effect

that evening exercise has on sleep. And this is something that we've started to look at within the whoop data because I know that many of the whoop users will do things like cold plunge and sauna after exercise, although we haven't, the field as a whole hasn't looked at whether this helps mitigate the sleep disruption relationship. There is like very interesting theoretical evidence that it may do so because one of the main consequences of high strain exercise is this over dominance of the sympathetic nervous system. We have increased heart rate and core body temperature in particular is heightened for a long

period of time. And if we can figure out a way to, I guess, regulate those processes and bring our body back down to resting homeostasis, and maybe that we can exercise up until two hours before bed as long as we manage the two hours after that in a certain way, that would be really cool. Yeah, and we'd love to do that study with you guys. But I think, you know, it's such an important point. Like, we're looking at just whatever people did for exercise and then whatever they chose to do between that exercise and sleep and then what happened to the sleep. And when you start to ask questions

like, okay, now let's look at the millions of nights of data where people exercise late at night and exercise intensely and then start to break that up by how were the people who had small sort of disruptions to sleep, different from the people who had large disruptions to sleep because, you know, we keep talking about the average effect, but of course there's a pretty wide distribution. Some people, like we were talking about, have seem to be very sensitive and others are not. And it's likely the case that it's not just, you know, some genetic predisposition to make me sensitive, although there might be some element of that. But it could also be that, you know, you and I go for a run. We get our core body temperature way up. And then I take a hot shower,

but you take a cold shower. And so your core body temperature is like closer to baseline. Mine's still jacked up. And then you sleep better than I do. Or you're refueling better or you're meditating. all those things that calm the sympathetic nervous system allow you to get into that parasympathetic state. So can we start to tease apart, not just that overall this relationship exists, but that this relationship, it is more of a sort of probabilistic predisposition that is completely canceloutable through good behavior. So you kind of stole my next question, but I'm going to ask it anyway. With access to either the data set we've been playing with or the entirety of all loop data.

What projects do you want to work on together next? Well, yeah, that would be really cool looking at recovery activities between exercise and sleep. One thing that an analysis that I did run that didn't make the final paper was I looked at with a high cognitive load within exercises are associated with changes in sleep, over and beyond the physiological strain that accompanies those exercises. So, for example, think about a competitive game of basketball where you're got teammates and you're competing against another team and you're communicating socially and you're also, you know, getting your competitive spirits up. And that has a certain effect on your psychology even after the game compared to just running on a treadmill or going for a swim, cycling on a stationary bike. So I categorized all of these exercises into high cognitive load and low cognitive load.

And then I looked at whether when these exercises are conducted at night, do they have differing relationships with sleep? And what I found was the high cognitive load exercises, delayed sleep onset, reduced sleep duration, and increased resting heart rate during sleep, independent of strain. So you take two exactly similar exercises in terms of strain, but you add cognitive complexity to one of them and you don't to the other. Well, it looks like that when your mind is racing, that's associated with changes in sleep. And it shouldn't be surprising. I mean, you think about elite athletes and the issues they have,

a lot of it is to do with the psychological aspect as well as the physiological aspect. They often lie in bed ruminating about the game, I should have done this, I could have helped here. And you can also see this the night before a game where sleep is also sometimes disrupted because they're nervous, they're contemplating, what am I going to do tomorrow? And there's no physiological strain attached to that.

So I would love to look at the psychological side and whoop has some really great data that can get at this. For example, I think you can log your gaming sessions, right? which would involve a lot of cognitive and psychological activation with very little physiological activation, I assume, unless you're really good. We did a lot of work, gosh, like five years ago with e-sport athletes. Esport athletes, yeah. But like basically professional video game players.

And their data is amazing. The extent to which like physiologically they look like athletes in a lot of ways and you think of them as kind of being sedentary, but they are so sharp. Their reaction times are like fighter pilots. And I think there's, yeah, a lot of interesting sports or activities that will let you kind of isolate some of these variables on wildly elite levels. So that would be fun data to play with. Well, I hope that we can do some of those studies and get you back here in a couple of years

and share those with everybody. But for now, thank you so much for being here with us today. Thank you for having me. If you enjoyed this episode of the WOOP podcast, please leave a rating or review. Check us out on social at Woop at Will Ahmed. If you have a question to answer it on the podcast, email us, podcast to WOOP.com. Call us 508-443-4952. If you think about joining WOOP, you can visit WOOP.com.

Sign up for a free 30-day trial membership. New members can use the code Will, W-I-L, to get a $60 credit on W-E-A-Saccessaries when you enter the code at checkout. That's a wrap, folks. Thank you all for listening. We'll catch you next week on the WooP podcast. As always, stay healthy and stay in the green.