Jet Lag Decoded: The Science of Time-Shifting for Runners

Jet lag isn't just feeling tired—it's a temporary circadian misalignment affecting hormones, temperature, digestion, and athletic performance that runners feel particularly strongly.

• Endurance performance depends on precise timing of biological functions that get disrupted during travel
• Core body temperature minimum sits 2-3 hours before wake time and is key to understanding light exposure timing
• Morning light moves your clock earlier, evening light moves it later
• Delay path (treating destination as behind rather than ahead) is usually faster and kinder for adjustment
• Time-shifting apps like TimeShifter and FlyKitt provide personalized schedules for light, darkness, and supplements
• Caffeine timing can help shift your clock but should be used strategically
• Keep naps short (20-30 minutes) to avoid disrupting nighttime sleep
• Place easy aerobic workouts during times you need to stay alert
• Save harder workouts for when your body temperature is higher, not near your temp minimum
• Older adults can still shift their clocks but it takes longer
• PR races are generally more successful when sleeping in your own bed without travel disruption

If you're traveling for races this season, stack your controllables by managing light exposure, darkness, and caffeine timing. Remember your body will adapt—you've done harder things and can still have a fantastic race experience!

Resources: 
NASA Technical Reports Server
Semantic Scholar PDFs 
PMC
Oxford Academic 
PMC
JCI Insight
Journal of Circadian Rhythms 
PMC
Cochrane
PMC 
PubMed
PMC
thenbsca.com 
Timeshifter®+1
Fount

Chapters

• 0:00 Introduction to Runner's Jet Lag
• 2:12 Circadian Science and Clock Shifting
• 5:27 Practical Tools and Time-Shifting Methods
• 9:52 Evidence and Apps for Jet Lag
• 15:02 Coach's Two-Track Plan for Sydney
• 19:06 Race Week Execution and Conclusion

Transcript

Speaker 1: 0:01

Hey friends, welcome back to Extraordinary Strides, the podcast where we lace up our sneakers, we geek out about all things running and have a whole lot of fun along the way. I'm Coach Christine, and today we're tackling something every traveling runner has wrestled with and as we approach that season the best season of all racing season it is jet lag. But don't worry, this isn't going to be a dry sleep lecture. We're diving into the actual neuroscience of why our body feels like a zombie after a long haul flight, how shifting 16 hours ahead for something like the Sydney Marathon scrambles up performance cues and, most importantly, what you can do about it. We're going to talk a little Huberman Lab style circadian science, walk through the two time shifting methods that I'm going to be testing on my own trip time shifter and fly kit and I'm going to give you practical, runner friendly tools to protect your sleep, your fuel and stride when your internal clock wants to do anything but so, whether you've got a race on the other side of the world or down under, or you just want to understand why Tuesday feels like a fever dream after a red-eye travel. Stick with me. Let's make jet lag less of a villain and more of a puzzle that we have all the tools we need to solve, survive and thrive upon.

Speaker 1: 1:13

Now jet lag. What in the world is it? Jet lag 101, specifically for runners, my friend. Jet lag is not just feeling tired, it is actually a temporary circadian misalignment, your central clock in the suprachiasmatic nucleus Did I say that correctly, dr Huberman? It sets our daily timing for alertness hormone release, body temperature, gut motility, performance, the whole nine. My friends, that circadian rhythm, and as runners we usually develop a pretty strong connection to our circadian rhythm. Peripheral clocks in muscle, liver, gut and heart also keep time. So when you cross time zones fast, these clocks drift apart. And that internal jet lag is why you can feel sleepy, foggy, hungry at strange times and why your legs may feel a little heavy. That's not even getting into the potential that you may have for being swollen from the running or from the travel. Just specifically jet lag on its own. So let's talk about why runners feel it a little bit more Well. Endurance performance depends on precise timing of cortisol, body temperature, neuromuscular drive and gut function. Peak strength and reaction tend to sit later in the biological day. After a time zone jump, your biological day and local day are out of sync and that will add up to slower perceived pace, higher rpe, clunkier mechanics and a little bit of a potential finicky gut. Good news clocks can be shifted on purpose. For the record, my friend, if you're looking at doing maybe even a Disney or a dopey race, in those races that start so early and you're coming from even just a couple of time zones away, this could really help you. I know again, we have a friend of the podcast who does time shifting before race weekends. So we're going to talk a lot about it.

Speaker 1: 3:03

But let's first get into circadian anchor points. Light input to special retinal cells sets the central clock. Long story short, that just basically means we need light in our eyeballs, my friend. Anytime we have that light, be it natural or otherwise, it's going to set that circadian clock in that anchor point. Morning light tends to move your clock earlier. Late evening light tends to move it later. Pretty simple, right? All the fancy science. That's essentially it. Core body temperature minimum sits about two to three hours before your usual wake time. What does that basically mean? That means that generally you're going to have a little tiny shift right before two to three hours before your usual wake time where your body temperature is going to dip just a wee bit. Light after that minimum moves your clock earlier. Light before it moves you later. This is the key lever to smart time shifting. This is also why it's super important that you minimize any additional light, be it from a cell phone or tablet or TV, any light that's coming into your bedroom upon those really important resting times.

Speaker 1: 4:13

Again, melatonin is that dark signal. You've heard about melatonin, I'm sure, and small, well-timed doses can help to shift the clock. Do not recommend melatonin for everyday use by any stretch of the imagination. But wrong timing with melatonin can make your jet lag worse. So proceed with caution. We'll talk about how to properly use it if you plan on using it. And exercise and meals are secondary time cues, they can help align your system when you place them near your new schedule.

Speaker 1: 4:42

So let's talk about the direction and the size of the shift. Well, for me, sydney in late August sits about 14 hours ahead of Eastern time zone and I'm planning on doing some travel to New Zealand, which is about 16 hours ahead of Eastern time zone. The brain can either advance 16 hours or delay eight. That's it. That's the way that our brain works. So delay path is usually faster and kinder. That means, though, behaving as a Sydney is eight hours behind rather than 16 hours ahead while I move my clock. Does that make sense? Good, we can talk about it specifically for you, but again, finding these methodologies through these different apps we're going to talk about that, but run a reality check. Is that sleep loss alone is going to potentially raise your injury risk? Raise perceived exertion basically means that time zone and your race day may feel a little harder. So your plan is to protect your sleep time, your light smartly, keep your tummy happy and time those key workouts like your shakeout runs after. Your biology is most cooperative.

Speaker 1: 5:49

Now, to find your temp minimum, take your normal waking temp and count back about two to three hours. That is a simple estimate for your nightly temperature. Low. Your light rules pivot around this point. So, to advance the clock, get bright light in the several hours after your temp minimum and avoid bright light in the hours before your temp minimum. Does this feel like a little too sciencey? Trust me, these apps are going to help you along the way. I use time shifting specifically for Tokyo. It really did help, especially in comparison to my trips for London and Berlin.

Speaker 1: 6:26

Okay, to delay the clock. You're going to do the reverse. You're going to get bright light in the evening before your tent minimum and dim or block light in the early morning hours just after local dawn. Practical tools outdoor daylight beats indoor light, we know that right. So getting out there and getting some natural light. But that doesn't mean that you have to do outdoor light. Any light can count If you're trying to minimize your exposure to light. That's when those dark glasses I wear my sunglasses at night may come to play, or eye masks as well. You could use some blue light filtering apps at night, only if it helps you to avoid those bright screens because, of course, darkness is still gonna be king. So prefer that full darkness over those light filtering, that blue light filtering on your apps.

Speaker 1: 7:16

Let's talk about my favorite thing ever and why I think I prefer one time shifting method over the other Caffeine and naps. Caffeine, late in the biological day is obviously going to delay our clock. I say this as I'm recording about three o'clock in the afternoon and have my delicious afternoon coffee standing right next to me. That I know I likely should not finish, but that can be your friend during the pre-trip delay strategy and your enemy once I actually arrive to my location or you arrive to your location, if it's used near bedtime. You want to keep any nap to 20 to 30 minutes. There's a whole lot of reason behind why you want to keep it to 20 to 30 minutes, but it has to do with your sleep cycle, and where you wake up within that sleep cycle is going to impact how you feel. But using a caffeine I know I don't know if you guys have heard of this before, but caffeine naps are a thing Using caffeine right before a short nap basically lets your body start to process the caffeine and it gives you a little bit of a boost once you wake up. So it's usually not ingested in a way where it's going to keep you up from sleeping, but it's going to help you once you wake up from that nap. However, avoiding napping in the parts of the day that you need to force yourself to stay awake to start that time shifting is going to be really instrumental.

Speaker 1: 8:41

Another way to really help with this is your exercise timing. So easy aerobic work is a safe way to push the clock. Place it during the part of the day that you're trying to be alert. You know what I'm saying, my friend. Like anytime you're feeling a little sluggish, that's a great time to do a little bit of exercise confetti. If you're trying to push your biological clock or circadian rhythms around a little bit, of course you're going to keep your hard workouts away from your temp minimum. So your body is cold and motor patterns feel sticky there. That's why sometimes again, this relates to so much of our everyday training as well Sometimes those harder efforts earlier in the morning feel a little sluggish, a little bit more sluggish. It's specifically because of that. It's too close to our temperature minimum. So you'll get more out of your tempo or your interval or strength workouts If they're a little bit later in the biological day.

Speaker 1: 9:30

Keeping that in mind that I'm also a big believer If you tolerate caffeine, caffeine can be helpful with this process as well. So now you've heard me talking about time shifting. Does it really work? What does the evidence say? Well, time shifting just basically means that we're going to deliberately adjust our exposure to light, darkness, melatonin, caffeine, sleep and meals on a schedule that moves your clock toward the destination before and after the flight, generally about three to four days before you're aiming to actually be shifted into your new time zone. Meal timing and exercise can also help with those nudges. So taking that into place and also knowing that why this works is because the human circadian rhythms in our clocks respond to time, light and melatonin and predictable curves.

Speaker 1: 10:21

Okay, the apps and kits and plain talk. Time shifter uses an itinerary and sleep profile to tell you where you should seek or avoid light, when to consider a tiny melatonin dose, when to use caffeine, when to nap, when to block the light, and it's built on peer-reviewed circadian phase response data. The reason why I love TimeShifter is because it gave me longer permission to have more caffeine. Seriously, I'm like I'm going to use the TimeShifter app over the Fly Kit app because I can have more caffeine. But Fly Kit also uses a similar type of app. It has a protocol and a supplement kit built to pair with schedule of light and dark. It has meal timing as well. Hydration, omega threes are part of the supplementation. Magnesium is part of the supplementation. A little tiny dosage of melatonin is part of the supplementation that gets sent your way. They precisely time the caffeine with a teensy little bit of sugar to help with again shifting that normal alertness versus sleepiness, and the goal with Fly Kit is to move the clock and lower inflammation during travel. That's why they have such a big supplementation that they add to their regimen Now.

Speaker 1: 11:30

Now what the literature says in short is that light at the right biological time shifts the clock by hours over a few days. Even brief period of bright pulses help. Now I will say that we have. There's a lot of science that says that older adults shift as well, with time shifting, but it takes a little bit longer or they don't do it as well. So as we get older, as we age, time shifting does become a little bit more difficult to achieve. Now also, melatonin being taken near the targeted local bedtime reduces jet lag severity across many trials. But small doses are usually going to be better and, as we know, as literature that came out a couple of years ago, melatonin, at least here in the United States at the FDA level, is not really widely regulated. So what your melatonin dosage says is in that specific bottle may not be actually what is in it. Sometimes it might be more, sometimes it might be less. So really finding a melatonin that you trust and know or you have highly recommended recommendations on is going to be really important if you choose to use melatonin.

Speaker 1: 12:34

Again, exercise timing out some of those easy runs or shakeout runs is going to be super important if you're using it for traveling, for your runcations or a specific race, and teams that travel. What we know is that teams that travel across time zones often perform worse, especially when traveling east or when playing at a biological disadvantage later at night. This is why I have said before and I'm going to say it again if you are traveling for a race, this may not be your PR race. Your PR race is usually. There's always going to be exceptions to the rule. I know I'm thinking about a couple of you. I want to point you out right now because I know there's a few of you that have broken the mold when it comes to this, but for the most part, most PRs would be more beneficial to chase after when you can control more of the different external circumstances, ie, sleeping in your own bed, being in your own natural rhythm that you had trained in, knowing all those different particulars, being able to even use your own bathroom and not having to worry about that aspect. So while it's not impossible to get a PR after traveling, it can be more challenging. I would say that this is also something that takes into place to where you are in your training journey. We know that newer runners tend to get bigger PRs earlier on because they have a performance peak. But neither here nor there it's still worth it to time shift because the physiology lines up and the data on athletes that we have seen favors this smart scheduling, the light control in those tiny, well-timed melatonin as well.

Speaker 1: 14:05

Now, this is a little bit of. We're going to talk now about why I'm choosing to tackle this two-track plan for my time shift. I'm choosing to do this because the first time around when I used Time Shifter, and while I have no complaints about how I felt, necessarily from a sleeping perspective, I did have tons and tons and tons of inflammation. So I'm choosing to utilize fly kit supplementation specifically to assist with that. We'll see if it works. I don't know. Stay tuned. I will definitely let you know. I'm not being paid from either of these folks, just letting you know what I'm trying to use, what I have researched to try to help me with Sydney. I have no PR goals, but I still want to be able to really enjoy myself and do the best that I possibly can on this entire trip.

Speaker 1: 14:51

So, with that said, let's talk about our little bit of our five day trip primer. We're going to shift our sleep and wake schedules. You're going to shift the bedtime and wait time. I'm personally going to shift mine a little bit later each day. Time shifter did that for me. I gave them all of my information on my travel, my flight plan, and it basically created what I need to do. So I've set my notifications to let me know. The Fly Kit does that as well. For the record, their app does it as well. I personally am going to use the Time Shifting app specifically, though, because I've already been there, done that, know that it worked really well for me using the supplementation from Flykit. Again, you're going to have to be much more mindful of your light exposure, your melatonin, your caffeine and training Training even before I leave is something that I'm taking into consideration and changing up a little bit as well.

Speaker 1: 15:45

Now, track A the time shifter style on the plane in days one, two, three, really important to try to use those naps. I'm not a good napper and I'm definitely not a good napper when I'm traveling, so I'm going to really try, on my side of things, to at least just use some dark sunglasses and to kind of minimize the light, close my eyes, maybe, do a little bit of restorative meditation, and then Fly Kit specifically, they do provide little bit of restorative meditation, and then Flykit, specifically, they do provide you with glasses to block the light. Again, they use magnesium, which I personally have in my everyday supplementation as well, they provide the melatonin. They are really big at timing out your hydration because of the cabin air being dry. We know that really, one of the reasons why people tend to have more immunity responses after travel is because that their nasal passages have been dried out. I'm also going to be utilizing a saline rinse to keep my nasal passages a bit more lubricated for this time around. And again, their time schedule is a little different than time shifter similar, but they have some different variables as well.

Speaker 1: 16:53

Now, both of these really want to make sure that I prioritize eating on the destination schedule as soon as I get on the plane, which thankfully they're not having me do that before I leave, because I don't know how to do a 14 hour time difference with eating. I leave because I don't know how to do a 14 hour time difference with eating. But a couple other things that are recommended for me to have with both of these different tracks is to include the utilization of ginger, peppermint or a little bit of carbonation to help travel, to help settle my travel stomach or your travel stomach, if this is something that applies to you, if you feel like a little bit, just not as comfortable on the plane with how it impacts your digestive system. So race week execution and how to judge success is that I'm going to follow that schedule of the time shifter app like it is my full-time job during that week. I am going to follow a supplementation schedule, a fly kit, like it's my secondary job that week, really prioritizing my hydration already going into it even a couple weeks out, still really prioritizing hydration and fueling, just like we would that's natural for us on races anyway and being mindful of what's really going to help, including those electrolytes. So what I'm going to do to decide which methodology I prefer or if it is gonna be a blend of the two, is that I'm going to track my sleep. I'm gonna track my morning HRV, how I feel on my shakeout runs and the race, and my stomach comfort and hunger timing. I'm also going to focus on my mood and how I feel in terms of my focus and clarity throughout the day and ebbs and flows of my energy. I think this is really gonna help me in determining what methodology is best and what I would recommend others to do, or if I even really 100% think this works, because there's so much that gets foggy after these travels are all done. There's also always that additional adrenaline of races and the fact that Sydney Marathon, specifically for me, right this very instant, not only is it a really wild time shift in terms of jet lag, but they also are the only world marathon major that starts as early as they do. So that's going to be quite interesting to navigate. So it's going to be interesting.

Speaker 1: 19:16

I would love, love to hear if you've tried time shifting, if you've tried either of these apps time shifter or fly kit, or the methodology of fly kit, the supplementation. I am I'm literally all ears on what you think about it, but I do want to remind you that if you are racing this travel season, if you're going to be going out for runs and races while you're out and about going and crossing time zones, you are not broken if things feel a little heavier or a little sluggish or you feel wobbly for a couple of days the clock will move, your circadian rhythm will reset. But do think of trying to set yourself up for success by stacking your controllables getting that sunlight at the right times, darkness when needed If you are so inclined. Trying those tiny little melatonin doses at the right times, darkness when needed If you are so inclined. Trying those tiny little melatonin doses at the right bedtime, or none if you don't like it. And, of course, trying to move that caffeine in a way that benefits you as well. Do also think about hence another really big, important reason why shakeout runs are so necessary for travel runs or travel races is getting those light, easy miles first and then afterwards, once you get your quality sleep in for a few days before you actually are meant to race, you could know that you've done everything you can. It's all within your possibilities and your control. You've controlled the variables, so just settle into knowing you've done harder things and you can still have a fantastic race day experience.

Speaker 1: 20:43

Now, if you are looking for your own set of resources a little bit of jet lag 101, I can recommend. There are tons of resources available out there and I'm happy to link those in episode notes as well, specifically some of the claims and discussions that I had here for you to do your own research, but I'm looking forward to again embarking on this right around the corner, and I want to say thank you for joining me on this deep dive into the weird and wonderful world of jet lag. We've learned that it's not just about feeling tired. It's truly an entire circadian orchestra that's playing out of sync. So it's also important to unpack that role of light, melatonin, caffeine and exercise and how to smartly shift our strategies to really help us in tipping the scales in our favor. Again, I'll put those two methods head to head on this experience and I'll come back and report to you which one I feel really helped move the needle if it's a little bit of both and how I felt along the way.

Speaker 1: 21:50

Let's be honest running 26.2 miles is tough enough without your biology thinking it's the middle of the night. So do yourself a favor, my friend if you are going to be doing some travel too, please, please, please, do look into these resources that I'm adding into episode notes. Reach out if you have any questions on how to make this something that you do for yourself, and if you love this kind of science meets stride breakdown. Make sure that you subscribe, share with a running buddy who might be racing abroad, and join our community newsletter so you don't miss the follow-ups. And, as always, thank you for being part of my found family of runners, because we do this better and a whole lot more joyfully together. Until next time, keep shifting those strides, stacking your science and running into your extraordinary you.