heat training: the hidden advantage for endurance cyclists

When cyclists think about improving endurance performance, the usual answers are simple:

Train more. Train harder. Recover better.

But there is another way to create a stimulus for adaptation.

Change the environment.

Heat training has become increasingly popular among endurance athletes because exposing the body to controlled heat stress can trigger a series of physiological adaptations that go far beyond simply becoming better at tolerating high temperatures.

For cyclists, this can be particularly interesting.

Because the goal isn't necessarily to become better at riding in the heat.

The goal is to become a better endurance athlete.

what is heat training?

Heat training is the deliberate exposure to elevated temperatures during or around exercise in order to create an additional physiological stress.

This can be achieved in different ways:

• training outdoors in hot conditions

• indoor cycling in a warm environment

• overdressing during controlled sessions

• passive heat exposure, such as sauna, in specific protocols

The principle is always the same:

increase thermal strain → trigger adaptation → reduce the physiological cost of exercise.

Repeated exposure to heat can progressively improve the body's ability to regulate temperature, circulate blood and manage sweating. Research and consensus recommendations show that meaningful heat acclimation can develop over roughly 1–2 weeks of repeated exposure, although some adaptations appear within the first few days.

why does heat make you stronger?

Riding in the heat makes exercise harder.

Your body has to deal with two problems at the same time:

produce energy + get rid of heat.

As your core temperature rises, more blood needs to be directed toward the skin to dissipate heat.

At the same time, your muscles need blood to continue producing power.

This creates additional cardiovascular and thermoregulatory stress.

The interesting part is what happens when this stimulus is repeated.

Your body begins to adapt.

the adaptations

Heat acclimation can produce several important changes.

increased plasma volume

One of the most consistent adaptations is an expansion of plasma volume.

More plasma means more fluid circulating in the cardiovascular system.

This can support stroke volume and cardiovascular stability, helping the body maintain cardiac output while dealing with thermal stress.

For an endurance cyclist, this matters because cardiovascular strain is one of the major limitations during prolonged exercise.

improved sweating

Repeated heat exposure can increase the body's ability to sweat.

This may sound counterintuitive.

Sweating more is actually part of the adaptation.

The body learns to start sweating earlier and more effectively, allowing heat to be removed through evaporation.

At the same time, sweat composition can change, helping the body conserve electrolytes more effectively.

lower cardiovascular strain

After acclimation, the same workload in the heat can produce a lower heart rate and reduced cardiovascular strain.

In practical terms:

the same watts can become physiologically cheaper.

This is one of the reasons heat acclimation is particularly valuable for endurance athletes.

better thermal tolerance

Perhaps the most obvious adaptation is also one of the most important.

The body becomes better at handling high temperatures.

Core temperature and skin temperature responses can improve, thermal comfort increases and exercise capacity in hot environments improves.

And this is where heat training becomes particularly interesting for cycling.

Because races don't always happen at the temperature you planned for.

but can heat training improve performance in cool conditions?

This is where things get more interesting.

Heat acclimation is clearly useful when you are going to race in hot or humid conditions.

But research has also investigated whether heat training can improve performance when the temperature is moderate.

One study involving trained cyclists found that 10 days of heat acclimation increased VO₂max, lactate-threshold power and time-trial performance in both hot and cool conditions. Plasma volume also increased.

However, the evidence is not completely uniform, and the size of the benefit can depend on the protocol, athlete and performance test.

So heat training should not be presented as a guaranteed shortcut to a higher FTP.

Instead, think about it as another physiological stimulus that can complement normal endurance training.

heat training vs altitude training

This is where the comparison becomes particularly interesting.

Both methods expose the body to an environmental stress.

But they are not the same stress.

Heat = thermal stress.

Altitude = hypoxic stress.

And because the stimulus is different, the adaptations are different.

Altitude training works primarily by exposing the athlete to reduced oxygen availability. This can stimulate erythropoietin and, in responsive athletes, increase red-cell and total haemoglobin mass, potentially improving oxygen transport. However, the hematological response varies considerably between individuals.

Heat training works differently.

It primarily creates adaptations around blood volume, cardiovascular stability, sweating and thermoregulation.

So which one is better?

It depends on the goal.

when heat training makes more sense

Heat training becomes particularly attractive when your target event is expected to be:

• hot

• humid

• long

• exposed

• difficult to cool down in

If you are preparing for a summer gran fondo, a long gravel race or an endurance event in southern Europe, heat acclimation can be a very logical addition to your preparation.

The evidence-based consensus recommendation is to use repeated heat exposures over approximately 1–2 weeks, with more recent IOC guidance suggesting around 60–90 minutes per session and at least four sessions per week during the acclimation phase.

when altitude training makes more sense

Altitude training is particularly interesting when the objective is to stimulate adaptations related to oxygen transport.

This is one reason why elite endurance athletes have historically used altitude camps.

But altitude training is more complex.

The altitude dose, duration, individual response, training intensity and recovery all matter.

And unlike heat training, simply going higher does not automatically mean better results.

Some athletes show substantial hematological responses to altitude, while others respond much less.

There is therefore no universal winner.

heat or altitude?

The answer depends on what you are trying to improve.

If your race is in 35°C heat, altitude training won't teach your body how to manage thermal stress.

Heat training will.

If your objective is to maximize adaptations related to oxygen transport, altitude provides a more direct hypoxic stimulus.

And if you are preparing for a long endurance event at sea level in moderate conditions, both strategies may have a role, although the evidence and individual response differ.

In fact, researchers have also investigated combining heat and altitude exposure because the two stimuli target different physiological adaptations.

The important concept is simple:

Don't choose the environment because it sounds harder.

Choose it because it creates the adaptation you need.

how to introduce heat training

Heat training should not simply mean taking your hardest workout and making it as hot as possible.

That can compromise the quality of the training session and increase unnecessary physiological stress.

A smarter approach is to introduce heat progressively.

Start with controlled exposure.

Monitor how your body responds.

Keep the core training objective intact.

Then progressively increase the heat stimulus as your tolerance improves.

For example, an athlete might use a series of controlled indoor sessions in a warm environment or combine normal training with passive heat exposure.

The goal is not to finish every session completely destroyed.

The goal is adaptation.

don't forget hydration

There is one part of heat training that cannot be ignored:

fluid and electrolyte management.

Higher temperatures generally increase sweat losses, and heat-acclimated athletes can actually become more efficient sweaters.

That means hydration becomes an even more important part of the strategy.

Starting sessions adequately hydrated and replacing an appropriate proportion of fluid and electrolyte losses is essential, particularly during prolonged sessions.

Heat training without a sensible hydration strategy can turn a useful stimulus into unnecessary stress.

the real advantage of heat training

The biggest mistake is to think of heat training as simply:

"training in hot weather."

It is more than that.

It is a controlled stress designed to force the body to adapt.

More plasma volume.

Better sweating.

Improved thermoregulation.

Lower cardiovascular strain.

Greater tolerance to heat.

And potentially improved endurance performance.

Altitude training attacks another limitation.

Heat attacks a different one.

And that is exactly why the comparison is so interesting.

performance is built from stress and adaptation

There is no single training method that makes an endurance cyclist better.

Fitness is the result of many different adaptations working together.

Training provides the stimulus.

Recovery allows adaptation.

Nutrition supports the process.

And environmental stress can provide another layer.

Heat training is not a replacement for good cycling training.

Neither is altitude.

They are tools.

The question isn't:

"Which one is harder?"

The better question is:

"Which adaptation does my next race require?"

Because performance isn't about doing more.

It's about creating the right stimulus at the right time.