Why a Marathon Doesn’t Prepare You for Extreme Hiking (and What Does)

On long-distance hikes, I have experienced something that genuinely surprised me: very fit marathon runners who were completely spent by kilometre 40 of a 55-kilometre hike.

Disciplined.
Highly trained.
Under 4 hours for 42.2 km.

And yet: they cracked.

Not because they lacked fitness.
But because they misunderstood the demands involved.

Because however similar they may seem at first glance, marathon running and extreme hiking are two different disciplines.

Different load dynamics

A marathon is an intense endurance effort lasting several hours. Most runners spend 3–5 hours at around 75–90% of their maximum heart rate, close to the anaerobic threshold.

The cardiovascular system is the limiting factor here.
The fuel tank is glycogen.

A 55-kilometre hike, on the other hand, often takes 9–13 hours. The intensity is generally much lower, around 60–75% of maximum heart rate. From a purely cardiovascular perspective, it often feels “doable”.

And that is exactly where the trap lies.

In a marathon, your system “burns out”.
On an extreme hike, it slowly “wears down”.

The heart is rarely the problem.
The tendons, feet, joints and your whole structure are.

The mechanical reality of long distances

A marathon involves roughly 35,000 to 45,000 steps.
Over 55 kilometres, that rises to 65,000 to 80,000 steps.
Over 100 kilometres, it is often more than 120,000.

Every one of those steps means:

• eccentric braking work in the quadriceps
• continuous stabilisation at the ankle
• stress on the plantar fascia
• compression in the knee

This strain is not spectacular—but it adds up.

A marathon runner primarily trains metabolic efficiency and pace economy. An extreme hiker needs structural resilience. Tendons and ligaments adapt more slowly than the cardiovascular system. That is exactly why many runners feel confident at the start of a hike—and then break down structurally later on.

Energy is more than a gel at kilometre 25

Let’s take a person weighing 75 kg.

Marathon

A rough rule of thumb in running is:
≈ 1 kcal per kg of body weight per kilometre.

For 42.2 km, that gives:

75 kg × 42.2 km ≈ 3,165 kcal

A large part of this energy comes from carbohydrates (glycogen).
When well stocked, the body stores around 400–600 g of glycogen, or roughly 1,600–2,400 kcal of available carbohydrate energy.

The rest must be replenished during the run or covered by fat.

This makes one thing clear:
A marathon is energetically tightly timed.

Extreme hiking

When walking, energy expenditure per kilometre is somewhat lower, but the distance is longer and the duration significantly greater.

Let’s calculate conservatively with around 0.7–0.8 kcal per kg per kilometre:

75 kg × 55 km × 0.75 ≈ 3,094 kcal

But that is only the energy used for movement.

On top of that comes your basal metabolic rate over 10–12 hours (around 800–1,000 kcal), as well as extra strain from a backpack, elevation gain or cold.

Realistically, that quickly puts you at:

4,000–5,000 kcal total expenditure.

So the difference lies less in the energy used for movement alone—
and more in the duration, structural strain and continuous energy demand.

In a marathon, you manage your fuel tank.
On an extreme hike, you have to keep topping it up—without your digestive system giving up.

What does this mean for preparation?

If extreme hiking is structurally limited, then training must be approached structurally too.

Not faster.
Longer.
Not harder.
More resilient.

Train time under load

Marathon training often includes intervals, tempo runs and long runs of up to around 30 kilometres. For extreme hiking, though, what matters is how well you can stay on the move for 4–6 hours at a low intensity.

That means:

• practising a deliberately slow starting pace
• longer sessions with realistic breaks
• accumulating time on your feet

The goal is not to maximise your heart rate.
It is to get used to the duration of the effort.

Build structural resilience

The heart adapts quickly. Tendons, ligaments and fascia do not.

That is why the following make sense:

• regular long walking sessions (not just runs)
• training with a light backpack
• eccentric strength exercises for the legs
• targeted foot and calf strengthening
• stairs or moderate elevation gain

If your feet “shut down” after 30 kilometres, a high VO₂max will not help you.

Learn to eat and pace yourself

Over 10–12 hours of exertion, eating early and regularly is crucial. Do not wait until you feel hungry.

Pacing discipline is just as important. If, after 20 kilometres, you think: “I could have started faster,” you have done a lot right.

If, after 20 kilometres, you already notice that the pace may have been a little too quick, you will feel it later.

The final third decides it

Extreme hikes do not begin at kilometre five. They begin where your structure starts to fatigue and your mind begins to negotiate.

Good training simulates exactly that:

• several hours of movement
• a short break
• then keep walking
• or another session under load the next day

It is not the first third that decides it.
It is the last.

The key takeaway

Marathon fitness is valuable. It provides a strong foundation.

But it is not automatically enough.

Extreme hiking is not a slow marathon.
It is its own discipline.

Less pace.
More duration.
Less heart.
More structure.
Less ego.
More pacing.

And that is exactly what makes the difference.