Physiological Adaptations (The Modern Training of Vojtěch Hačecký)

Trick the Brain

Summer is approaching—and even if May didn’t quite feel like it, the heat is coming, and not everyone handles it well.Still, we’ll be riding—and quite possibly racing—in these uncomfortable summer scorchers. So how can we acclimate to extreme heat (or, on the flip side, to cold or high altitude)?

Physiological adaptations, as these processes are called, are mainly about manipulating the mind and preparing the brain for external conditions different from what we’re used to. We learn to perform in circumstances that are extremely uncomfortable for the body, and we try to convince the brain that it’s still okay and that it shouldn’t stop us. The brain is the primary protective mechanism, monitoring the body’s core temperature, and when it gets too high, it tries to shut us down—often through pain. With controlled adaptation, you subconsciously persuade the brain that nothing is wrong.

The key question is how meaningful physiological adaptations are for the average amateur athlete. There is a kind of training needs pyramid, and among the three essential building blocks, heat adaptation definitely isn’t one of them. It’s certainly worth considering, but if someone personally feels that extreme conditions are a major limiting factor and has their main race of the season scheduled during likely hot weather, then they need to address it.

On the other hand, we must not lose sight of the bigger picture and focus solely on adaptation, forgetting to train in the process. That would obviously be nonsense. Adaptation only has an effect when you have a solid training system in place and want to move a bit further, improve, and manage another potential performance factor.

An amateur thinking about focusing on heat acclimation has things a bit easier. In recent years, summers have been hot enough that this acclimatization process can be done at home in the Czech Republic. In that case, however, one must deliberately seek out exposure to high temperatures—like going for a ride at midday. This can be a slight complication for someone with a regular work schedule. That person, logically, won’t be able to take advantage of the hottest parts of the day unless they rearrange their work so they can train during their lunch break. That’s assuming they have a lenient employer and can manage at least an hour of training outdoors around noon.

Even that can be somewhat beneficial, but it’s important to understand that exposures under 45 minutes don’t have a significant impact on adaptation. On the other hand, it’s not necessary to push the exposure past 90 minutes unless it’s part of a regular training session like the pros do. For that, weekend rides are an obvious option—offering nearly unlimited use of heat exposure.

Additionally, heat acclimation can include hot water baths where the water temperature is kept at 40°C and you soak for at least 30 minutes, deliberately overheating the body. This method can also train the body to tolerate feelings of excessive heat. Another option is to use a sauna, even in summer.

How can heat adaptation be done safely? It’s important to keep repeating that the training intensity during hot weather should be low. Intensity should not exceed the first ventilatory threshold—so basically endurance level. This is because we aim to expand plasma volume, increase blood volume, which requires staying highly hydrated at the same time.

High heart rates simply aren’t desirable because we also need the muscles to cool themselves, which obviously doesn’t happen at high intensities. What was a decisive factor at the Tokyo Olympics will also apply to amateurs—we need to fine-tune movement economy to make it as energy-efficient as possible. In heat—or cold, or any extreme condition—what will matter is whether the body prioritizes performance or thermoregulation.

It’s about how smoothly you push the pedals, which may or may not be a measurable indicator. More than anything, it’s about how the body has learned to use energy efficiently by activating different muscle groups. This isn’t something an amateur can usually measure or determine on their own—it requires lab testing or portable spiroergometry. What I mean is, if we want to produce 200 watts at the pedal, the body might have to generate somewhere between 900 and 1100 watts total—and the rest is simply lost as heat.

You can’t trick movement economy. It’s developed first at low intensity. Movement economy comes from the number of contractions and relaxations of muscle fibers—from how many pedal revolutions your legs perform over their lifetime. Because before each new pedal stroke, the body tries to do it better. The body is programmed to conserve, and the more often we repeat a movement, the more fluid, elegant, and efficient it becomes.

Yes, we’re encouraging low intensities here, but at the same time, we’re training for a race that won’t be slow. So, these different adaptations need to be built into a longer training period, carefully thought out, and approached with the understanding that during the acclimation phase, you won’t be training intensity. You have to plan your training so that for 8 to 10 days, you can afford to ride without intensity—just moving, just acclimating.

Don’t worry—you won’t lose your speed after a week of slow riding. In fact, there’s a greater risk in overdoing it—we don’t want to boil the body. And the body will quickly remember. A week without intensity won’t harm a pro or an amateur; in the end, it’s likely to bring a positive effect—slowing down training often leads to a better outcome.

The timing of heat acclimation will be crucial. If we assume that the key races for amateurs and masters happen in summer, then ideally you should start as early as twelve weeks before the championship. Do one to one and a half weeks of heat training, then go back to your regular routine for five to six weeks, then insert another heat phase, and maybe one more before the peak, depending on how you feel. But before an important race, I’d take two to three days of normal conditions—no heat exposure.

One of the key parameters in adapting to hot weather is the ability to sweat and thus cool the body. That’s why people drink cold and sweet things—something to slightly cool the internal environment while providing energy. The hotter it gets, the worse energy bars will taste, and even the concentration of electrolytes in your drink will decrease—because the taste will start to bother you. And once something bothers you, it becomes a limiting factor. But even the pros don’t drink just water—most teams now have precisely calculated how many grams of carbs each rider needs to consume.

Proper hydration can, according to one opinion, be measured by weighing yourself before and after training—the difference should not exceed 4% of body weight. Another opinion is that this is relatively meaningless, but for amateurs, it’s probably the simplest way to monitor hydration. Try to drink back the fluid you lost—even a little more—but gradually, because kidneys aren’t designed to filter liters of water at once. So ideally, about 250 milliliters every 15 minutes.

The opposite is cold, which is much harder to adapt to—and usually isn’t done at all. Not even cyclocross riders do it. In cycling, there’s realistically no need for it—unless you’re someone like Honza Kopka riding a fat bike across Alaska, but even then, it’s probably not a deliberate adaptation. Just as the leaner among us will have an easier time adapting to heat, the bigger riders will fare better in the cold.

But the principle is the same: by spending time in cold conditions, we can prepare ourselves for the cold. Like stepping into a freezer. But this mostly affects the mind and perhaps slightly improves capillarization—so the body can stay functional in winter and keep muscles warm. But it won’t bring any significant physiological gains.

We could try the most common method—cold water exposure—which has seen a huge boom lately. But in terms of scientific backing, it’s even worse than heat adaptation. Most studies are too short to reliably assess the benefits of cold exposure. That’s why the conclusion tends to be that it brings no real benefit. It lowers cortisol levels and makes you calmer, but that’s about the only proven effect. Empirically, we know it works and that cold-adapted people tend to get sick less often—but it’s hard to prove because we lack a proper control group.

A special case is adaptation to high altitude and training in thinner air. You might think there’s no reason to worry about this in the Czech Republic—we don’t have any mountain stages above 2000 meters. But there are races—if you plan to compete in Austria or Italy, you’ll definitely climb into mountain passes above 2000 meters.

But you can’t train for that in the Czech Republic—or at least not as an amateur. A hypoxic tent is a complete non-starter, and so is a hypoxic mask. Not because it’s financially impossible—but because no one has the time. For tents or masks to have any effect on hemoglobin production, exposure needs to be at least 14 hours per day—ideally 16. And that’s just not realistic. Even pros struggle with it, and they don’t have day jobs. Amateurs simply won’t have time for that. The only option is to go abroad to the mountains—or take a vacation and spend 14 days in a tent. But at that point, you’re better off spending the money and actually traveling somewhere. Especially in today’s post-COVID world...

If someone is considering altitude adaptation, they need to understand that one stay won’t cut it—it would have to be a program of repeated stays at altitude, with a minimum total duration of around 300 hours. I don’t know if anyone can manage that. Sure, there are individuals who would find the time and money, and since cycling is a deep passion for them, they’re willing to go that far. But your average amateur won’t be able to follow such a plan.

An alternative could be training in the heat—or simply doing long endurance training, which leads to increased plasma volume. If you’re well hydrated, you increase blood plasma volume, which dilutes your blood—and the body responds by trying to thicken it again. So in the long run, even plain old endurance training with lots of hours will increase total hemoglobin mass in the blood. That’s the most viable option for amateurs to do something about adaptation. But again—it takes time. And time is the most expensive commodity today.

**** breaking point ****

There is a kind of pyramid of training needs, and among the three fundamental building blocks, heat adaptation definitely isn’t one of them.

What was a decisive factor at the Tokyo Olympics will also apply to amateurs—we need to fine-tune movement economy to make it as energy-efficient as possible. Because in heat—or cold, or any extreme condition—what will matter is whether the body prioritizes performance or thermoregulation.

If we want to produce 200 watts at the pedal, the body might have to generate somewhere between 900 and 1100 watts total—and the rest is simply lost as heat.