Every July we watch superhuman athletes conquer the most brutal climbs in the world. Vontu Lelia. We see them sprinting through valleys in line outs pushing their bodies to the absolute brink.
But what if I told you there's a training hack? Don't worry, it's legal. It's sciencebacked and it might be the secret weapon behind tour to France domination in recent years.
I'm talking about heat training. Heat training isn't just about surviving in hot climates. Research now shows that targeted heat exposure can increase your hemoglobin mass by 3 to 4%.
Boost your V2 max by roughly 6% and wait for it. Add 20 to 30 watts onto your functional threshold power. That's absolutely huge.
The best riders in the world, Taday Yonas, they're all overdressing. They're sweating in saunas. They're wearing this little clip onto the side of their heart rate monitors you might have seen called core.
All tracking their core temperature. Today, I'm going to dive deep into the science. I'm going to break down and show you the exact protocols and the pro secrets.
We'll share a step-by-step heat training plan that you can try at home. Are you ready for this? Let's dive in because this is going to really change how you train.
For decades, altitude training has been the gold standard for boosting red blood cells and oxygen carrying capacity. Altitude gains fade quickly though once you return back to sea level and that's a problem when you look at the tour to France. This year especially the first week was through northern France with none of the higher mountains until the second and third week in the race.
So your altitude exposure happened weeks ago and the benefits of that exposure are now fading as you enter into the high mountains. This is where heat training enters. A 2024 study by Bent Runstad looked at 18 elite riders who just completed a three-week altitude training camp.
Half of them added 50 minute heat sessions per week. Sorry, three 50-minute heat sessions per week in the weeks that followed, aiming to raise their core temperature to 38.5°.
The heat trained group, they maintained their increased hemoglobin mass for three and a half weeks after they finished it. and the control group, they lost almost all their gains. Heat training effectively locked in and extended the benefits of the altitude training.
In this case, Dr. Carsten Lundy, a leading heat training researcher, calls it one of the most effective interventions we know. In his words, increasing hemoglobin mass by 3 to 4% through heat training is the equivalent of months of altitude exposure.
That's a huge return on investment for just a few weeks of sweating. Now, you might think this all sounds like pseudocience, and honestly, I was pretty skeptical before I started digging into the research, but virtually every World Tour team has tested this by now. Core company, which makes the little white sensor that clips onto the heart rate strap that you might have seen, that's the most popular wearable in the core temperature sensor space at the moment.
And they say that nearly all World Tour teams have used their device at some point, and that seven teams were officially supported by them in 2025. 17 of the 21 tour to France stage winners this year were won by wearers of core devices. If you go on to their website they have a who's using core page and it includes quotes from some previous podcast guests like the Bora Hansrove head of performance Dan Lurang.
He said the core sensor changed the way how they decide pre-race warm-ups. They use it to determine fluid intake and they're even using it to inform clothing choices which is wild. heat adaptation.
It became mainstream partly because of the Tokyo Olympics. If you go back and I'll link below one of my conversations with Alex Dowset, he spoke to me on the runup to the games on the podcast about sweating it out for the first time. The protocol sounded brutal.
But it wasn't just like GB who were doing this. GB as they often are on the cutting edge of informing new technological trends. But the practice wasn't confined to GB or even just national federations.
World Tour teams had started playing around with it. Pro teams like Lotto Destiny started using heat training not just to prepare for hot races like GB were doing in Tokyo, but to race faster in any climate. Research led by Bent Ronstad showed that five 50-minute heat sessions per week for five weeks increased hemoglobin mass by 3%.
Another study by Santiago Lorenzo found that after only 10 days of heat acclamation, trained cyclists increased their V2 max by 8% and improved threshold power by 5%. There's a lot of different studies going on, but they're all showing pretty significant gains across V2 max, threshold, time to fatigue. It's wild.
You can't ignore it. Sports scientist Carsten Lungby argued that heat training is more effective than altitude training because more people seem to respond to a heat stimulus. Altitude training seems to have a genetic component.
It's broken largely into two groups. You have genetic responders to altitude training and genetic non-responders to altitude training. Heat training doesn't seem to be like this.
Almost everybody that I saw studied had some sort of response to heat training. Increasing hemoglobin mass by just a few percentage. Might sound familiar.
This is similar to what banned substances like EPO offer. But now we have a legal and an ethical way to do this. Okay.
So how do you actually do this? When you exercise in a hot environment or you deliberately overdress, your core temperature rises faster than usual. At around 38.
5° C, your body triggers this cascade of adaptations. One of the earliest responses is increase in blood plasma volume. More plasma means more total blood which improves cardiovascular stability and oxygen delivery.
Repeated heat stress over 7 to 14 days increases plasma volume, improves sweating responses, lowers core temperature at a given workload, and reduces perceived exertion. Basically, your cooling system becomes more efficient. Heat stress also stimulates the production of new red blood cells.
The same adaptation targeted by altitude training. Dr. Lundy explains this increase in hemoglobin mass is like natural EPO.
Two to four% gains in 5 weeks can be achieved at home in your home trainer. I'm going to go through this protocol in a second. That additional hemoglobin, it boosts oxygen transport.
It raises your V2 max and your ability to sustain high power for longer. A Norwegian meta analysis, that's like one study that studies all the studies, found that heat acclamation improves endurance test performance by an average of 23% and increases V2 max by around 6%. As your body adapts, it also learns to sweat earlier.
So when you're riding, if you're previously don't break sweat for 40 minutes, now it seems to happen a little bit earlier than that. And importantly, it's you sweat more effectively. the sweat becomes less salty, saving electrolytes, and your heart rate drops by on average five to eight beats per minute at the same intensity.
Let's lay out the process as to why this works because it's very interesting the underlying physiology as to what actually makes this happen or makes us get these adaptations. Heat training changes how your muscles use energy. Studies show that it improves fat utilization during submaximum exercise.
That means it spares pre precious glycogen for later on in a training session or a race. Mitochondria become more efficient, increasing ATP production and reducing oxidative stress. With more red blood cells, improved plasma volume and better term regulation, you can sustain power for longer, thus delaying fatigue, pushing out that point to which fatigue.
Heat adaptation also lowers your core temperature set point. Once adapted, you start sweating at a lower temperature and your skin blood flow increases by 15 to 20% which helps you to dissipate heat. This means you're less likely to overheat in a race and you can maintain a lower heart rate at a given power which is just good news.
One of the really cool things is the speed at which this adaptation happens though. It doesn't take a really long time. Heat adaptation happens faster, way faster than altitude adaptation.
The first phase is like phase days one to three and we see plasma volume expand. The second phase we look at is like phase days four to seven and that stimulates new red blood cell production. The third phase is like days 8 to 14 and that stabilizes and optimizes these changes.
So in 14 days there is serious adaptations taking place. The main adaptations occur in the first week and full adaptation happens after those 14 days. But even short protocols yield benefits.
Studies show that heat training for under seven days, it begins to improve temperature regulation and performance. However, sessions in that 14-day space seem to produce more pronounced gains. Let me now show you how the pros are using it, and then I'll walk you through an exact protocol which you can take, bring it home, copy it, and run in your home trainer setup to see if heat training is something you want to try experiment with.
In the run-up to the tour to France, social media was flooded with these images of Pagatcha on his indoor train and wearing full winter kit, scarf, winter coat, everything. And a lot of us were wondering what's going on. Why is he doing this?
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Back to the show. So after dominating the 2024 season, I don't even know how many races he won, a lot, but he wanted to keep improving. His new coach, Zavier Zola, prioritized heat adaptation going into 2025.
Rather than just preparing for hot days in France, they used heat training to boost hemoglobin. Pogata became a regular user of the core temperature sensor, monitoring his core temperature during sessions to ensure he hit that target zone. and core temperature.
They break it down into zone one and zone two where you want to keep your core temperature if you're racing for optimal performance and zone three that's in that 38.5 degree in and around there where all the adaptations seem to happen. That's where you want to be sitting during training sessions.
In an interview with Cycling Weekly earlier in the year, Pagatcha admitted that he always struggled in extreme heat, but he said that heat training had now become a big thing in cycling. UAE Emirates head physiologist Joran Swart noted three heat sessions per week over six weeks increases hemoglobin mass by about 4%. That's the same gain you'd expect from about 3 weeks on Mount Tid at around 2100 m of altitude.
Squirts protocol involves riding indoors on a trainer in a small room without a fan, wearing winter clothing, and holding your core temperature at around where I said 38.5° for 30 to 40 minutes using a core device. Yonas Vindergard also seemed to turn to heat training in the run-up to this year's Tour to France as he tried to dethrone Pagatcha.
Yonas was seen training in 30° heat, fully overdressed, long sleeves, tights, scarf, everything. similar reasons for this. Overdressing forces the body to respond to that thermal stress leading to the plasma expansion and improved sweat response and reduced heart rate at a given power.
I just want to be really clear what we're talking about here. Heat adaptation isn't just about surviving hot stages. It improves aerobic efficiency even in cool weather.
In other words, you get fitter in all terrain, in all weather by training in heat. Now, as an Irish person, I couldn't summarize what the pros are doing in the 2025 Tour to France without talking about Ben Healey. It was our first yellow jersey since Steven Roach in 1987.
Ben Healey just allround legend had an unbelievable tour to France. But EF Education Easy Post, they have one of the most comprehensive heat training protocols out there. In an interview preour, Dr.
John Greenwell explained that they test riders in heat chambers to measure sweat rate, sodium loss, and core temperature. They then prescribe two approaches. Active heat training, riding indoors, like we talked about, and I'll break down in a second, without a fan, wearing extra uh layers, and raising that core temperature to 38.
5°. They were doing it for 45 to 75 minutes. But they have a second type of heat training called passive heat training with hot baths at 40° C.
We're going to put a pin in that one and we're going to come back to it before the end because this one is interesting mainly because I've tried the active one and it really sucks and it's hard to do. So, this sounds a lot less painful. So, let's come back to it.
Now, we've seen how the pros are using heat training. Let's walk through a practical plan like something you can copy and paste the template. Now, before we dive into this, it must be said that heat training does carry quite a few risks.
Dehydration, electrolyte imbalance, heat illness. So, do proceed caut cautiously with this. You're going to need an indoor trainer or stationary bike.
Small rooms are better. Increase the room temperature to 25 to 30° C. Use a space heater if you need to.
Alternatively, you can heat train outdoors on a hot day, but ensure you do have shade afterwards and cold fluids because cooling down when you try this outdoors is super hard. Step two is overdressing. winter kit, long sleeve, tights, hats, or a boiler suit to trap that heat.
Don't use a fan. The goal is to raise your core temperature quickly. Here, we're going to monitor the temperature.
We want to know how high the core temperature is going up. A core temperature sensor like core device clips onto your heart rate strap and it transmits real-time data to your bike computer. If you don't have one, you can use an in-ear thermometer or if at a push you could rel you could rely on perceived exertion, but I don't really recommend that one.
And if you are doing it, air on the side of caution. You're going to need to hydrate during this and have at least one liter of room temperature water or electrolyte per hour. Don't use cold fluids because they can blunt the adaptation to the heat training.
Use a towel to wipe away sweat and importantly weigh yourself before and after the session. Aim to lose no more than 2% of your body weight during a session. Several studies and teams seem to converge on a simple protocol.
Raise your core temperature to about 38.5° C and hold it to 30 for 30 to 40 minutes. So, how I would look to do that, and again, this seems to be a convergence of how a bunch of teams and physiologists are recommending it.
warm up for 5 to 10 minutes right at zone one easy pace until you start to feel warm. Keep your core temperature device obviously turned on so you know what your core temperature is. Then we're going to do a 20inut what we'll call a heat ramp where you increase power up to zone 3 while wearing all this winter kit.
Again closely monitoring your core temperature and it should climb towards that 38.5° C. If you hit 39° C that's when you can start backing off.
Then we head into the maintenance phase. 30 to 40 minute maintenance phase. Once at 38.
5 degrees, reduce power enough to sustain that temperature. There might be a little bit of playing around with it. For me, it's normally the top end of zone one, the bottom end of zone two, where I seem to be able to sustain that temperature after the heat ramp.
You'll feel uncomfortable. It's pretty miserable. I won't lie to you.
You're going to feel hot. You're going to sweat profusely. Drink water with sodium throughout it.
heart rate will be typically 10 to 20 beats. I've even experienced a 25 beats higher than normal at the same power. So, you don't need to worry about that.
Then you're going to cool down. You're stripping off all the layers. This is after the maintenance phase.
Stripping off all the layers, getting some windows open, turning off the heat, and having some cold fluids. Here, you want to spin easy in zone one power just to flush out those metabolic byproducts of the session. I would start with maybe condensing that protocol to 60 minutes including the warm-up and cool down for the first five days, then gradually extend it from 75 to 90 minutes over the next week.
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I'm going to put that in the description down below. And now if you want to try passive heat exposure like EF Education and Ben Healey, hot bats and saunas are effective alternatives. The EF program uses 40° C bats after training.
Cyclists immerse themselves for 20 to 45 minutes gradually increasing the duration. And research on onto this uh particular area was from Michael Zuralu and he found that hot water immersion after exercise produced heat adaptation similar to training in the heat. Saunas also work, but they're harder to control and can cause dehydration.
A simple home protocol that you could try for passive heat exposure is to fill a bathtub with water, 40 to 42° C water. So, you're going to need a water thermometer for this. Immerse yourself up to the neck.
Stay calm because it is pretty warm when you jump into that. Monitor your heart rate. Drink 500 to 750 mil of fluid during it.
I would begin with maybe 20 to 25 minutes for the first three days, extending 30 to 35 minutes in days four to seven and then aim for 45 minutes by the end of week two. perform this three to five times a week as a substitute or if you're really feeling daring as a supplement to active heat training. Some teams use heat training to extend the benefits of altitude camps.
If you're in that sort of situation where you have the benefit of going to altitude exposure or maybe it's a family holiday and it just happens to be at altitude and you're like how can I extend the benefits of altitude exposure? Well, the little trek coach, Matteas Wreck, he explained they use a hybrid heat altitude strategy. After an altitude camp, riders complete 10 to 14 heat sessions lasting 40 to 50 minutes to maintain that hemoglobin mass.
In a 2024 study, athletes who used heat training after an altitude camp, they seem to retain their hemoglobin gains, while those who didn't lost 71% of their improvements. So, it really does it really does extend it, and it really does seem to matter. This all seems so positive so far, but there is a downside to this.
Well, one, I've tried and it really does suck. Heat training is not that fun. It's not that glamorous, but heat adaptation can also cause heavy sweating.
Now, sweat contains 500 to 1,000 mg of sodium depending on what type of sweater you are. It actually is worth getting a sweat analysis test as a sidebar at some point. I'm planning to get one this winter myself.
So, plain water isn't going to cut it because it doesn't replace the sodium. You're going to need to use an electrolyte mix containing sodium, potassium, and magnesium, and maybe some carbohydrates. Drink room temperature fluids during these sessions to maintain hydration without cooling your core and blunting that response.
After the session, make sure you've weighed yourself before, weigh yourself after. If you lost more than 2% of your body weight, you risk heat illness. Always replace at least 150% of your weight lost over the next few hours.
So that means if you lost 1 kilogram of weight during the session, aim to drink 1.5 L of water. Include salty foods like broth or salted potatoes to replace those electrolytes.
Heat training pushes your body close to its limits. So pay attention to these warning signs. Core temperature above 39° C, stop immediately.
Dizziness or nausea, that signals overheating and hydration, again stop. If you stopped sweating, this is a real red flag for heat stroke. Excessive weight loss over 2% indicates severe dehydration.
Confusion, headache, are also signs of heat exhaustion. If you experience any of those, stop, cool down, rehydrate. If it's super bad, go to the doctor.
Heat training, it might sound extreme, and it doesn't feel brilliant, but it is grounded in solid solid science. By deliberately raising your core temperature and forcing your body to adapt to that, you can unlock massive gains in hemoglobin, plasma volume, V2 max, and metabolic efficiency. Paga, Yonas, the entire world tour seem to be incorporating it into their preparation.
Often with the help of sensors like that core one we talked about to monitor thermal load. Research shows that just a few weeks of these heat sessions, it can yield improvements which are comparable to and exceed altitude training improvements. If you're ready to experiment, I do urge you to start cautiously with this.
Don't do it near your target event and do it in a controlled manner. I I like that expression graded adaptation. Integrate one or two heat sessions per week into your training.
Monitor your temperature carefully. Use if if you're using Training Peaks, use the little feedback below to monitor how you're feeling. So you can go back and if you do start going well after, you can say, "Okay, well, here's why I'm going well.
" Stay on top of your hydration. Over time, you might even find that heat not only makes you tougher in the sun, but it also transforms your fitness all year round. If you decide to try heat training, please do let me know because I'm really curious.
I'm experimenting a lot with myself and clients at the moment. So, let me know in the comments below this video when you do experiment with it and let me know how you found it. Thank you so much for tuning into this video and if you found this deep dive valuable, please hit the like button.
That helps us get it out to more people. Take the link to this, share it into your club WhatsApp group, encourage your buddies to try it. Don't forget to subscribe to the channel so you don't miss these upcoming experiments.
And remember, sometimes the best way to get faster is just to turn the heat on in the house. There's another video up here which I know you're going to love. And I'll chat to you next day.