Whether you like it or not: more than half of a HYROX consists of running. And that’s exactly where many athletes lose time. Especially HYROX athletes with a strength or CrossFit background have rarely had any running-specific training.
So the question isn’t whether you can run faster in HYROX, but how to train for it intelligently— in combination with the workouts.
In this article, I’m assuming a HYROX athlete who can handle the stress of running: someone who can consistently and injury-free run 30–40 km per week.
Not there yet? Then step one is simple: build running resilience. Without a sound foundation, there’s no room for specific stimulus.
Determining zones
The next step: training with structure. That starts with determining your training zones.
This can be done in two main ways:
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via the algorithm of your sports watch
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or through a run exercise test
If you want to take it seriously, a performance test is worth its weight in gold. You don’t just get your personal heart-rate and pace zones, but also insight into factors like running economy: how efficiently you run at different speeds.
Training based on zones brings:
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logic to your training
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clarity in intensity
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and most importantly: more progress with less risk of injury
Run faster in HYROX: crash course exercise physiology
HYROX, no matter how explosive it may feel at times, is at its core an endurance sport. To understand that, let’s start with a brief physiological explanation.
To be able to run, your body needs to produce ATP. This happens through three energy systems:
1. Anaerobic alactic system
This system works without oxygen and without lactate production. Creatine phosphate (CP) stored in the muscle cell is rapidly converted into ATP. That ATP is the energy source for your muscles and allows them to perform work. Ideal for maximal strength and sprints, but the supply is depleted after 6–10 seconds.
→ Suitable for a 100 m sprint, not for the running segments of HYROX.
2. Anaerobic lactic system
This system also works without oxygen, but also produces lactate. Through glycolysis, a glucose chain is broken down, releasing ATP and producing lactate.
And this is where perceptions often go wrong: lactate is not a waste product, but a valuable fuel for the aerobic system.
3. Aerobic system
The lactate produced in fast-twitch muscle fibers can be transported via the bloodstream and through exchange between muscle fibers to:
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slow-twitch muscle fibers
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the heart
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the mitochondria
There, together with oxygen and fats, it is burned again.
In layman’s terms:
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your anaerobic system is the lactate tap
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your aerobic system is the lactate drain
The bigger that drain, the longer you can sustain a high pace.
That’s why 80–90% of the training time of successful HYROX athletes consists of endurance training—more than many HYROX athletes are used to, especially those with a strength background.
The good news: running-based endurance training can be easily combined with:
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SkiErg
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RowErg
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cycling (the safest way to build volume)
Even among the Elite 15, you see endurance volume increasing, often at the expense of strength training—because maximal strength is rarely the limiting factor at this level. The training load of Elite 15 athletes such as Tim Wenisch, Hidde Weersma, Jake Dearden, Lauren Weeks, and Joanna Wietrzyk is 15–20 hours per week, the vast majority being aerobic. Anaerobic stimuli are carefully dosed. The top athletes experiment and vary endlessly with combinations of running and HYROX-specific intervals. No one has the golden formula, as Hidde Weersma confirms this in this interview.
Run faster in HYROX: run intervals
Endurance training alone is not enough.
During HYROX, you run under fatigue and at higher lactate levels than during a standalone 10 km race. Lactate measurements I’ve taken during HYROX simulations clearly show that lactate builds up during the workouts. While running, you then have to process that lactate.
Below you see the heart rate and lactate values of a HYROX athlete during a HYROX simulation. A few weeks earlier, she completed a run exercise test. Her lactate threshold was 4.1 mmol at a heart rate of 175. Throughout the entire HYROX simulation, her lactate was higher than that 4.1 mmol. With every HYROX athlete for whom I’ve conducted both a running performance test and a HYROX simulation with lactate measurements, I see the same pattern. That’s how much a HYROX demands from your anaerobic system.
Running faster in HYROX requires:
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a large aerobic system
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a perfectly trained lactate shuttle
Welcome to the world of MCTs.
What are MCT’s?
What are MCTs?
MCTs (Monocarboxylate Transporters) are membrane transport proteins that move lactate and hydrogen ions (H⁺) across cell membranes.
They are essential for the lactate shuttle.
Let’s go down the MCT rabbit hole. There are two types:
MCT1
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transports lactate into the cell
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mainly found in slow-twitch muscle fibers and the heart muscle
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helps to burn lactate
MCT4
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transports lactate out of the cell
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mainly found in fast-twitch muscle fibers
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supports the glycolytic process—carbohydrate breakdown—by removing lactate and hydrogen ions (H⁺)
Run faster in HYROX: The lactate shuttle
According to George Brooks’ lactate shuttle model, lactate is:
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not a waste product
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but an essential energy carrier
Lactate produced in fast-twitch muscle fibers is transported to the mitochondria, where it serves as fuel again. MCTs make this process possible.
HYROX, therefore, is not about avoiding lactate, but about efficiently transporting and using it.
Training your lactate shuttle: HYROX-specific intervals
A recent hobby of mine is mapping out the EMOMs, WODs, and running-specific intervals of Elite 15 athletes. There are as many variations as there are athletes—everyone has their own favorite sessions. Most of them do one running-specific interval session per week and one workout where HYROX elements are alternated with running or ergometer blocks. The common denominator is that both aim to improve the lactate shuttle. And just as importantly, they teach the athlete to run under the HYROX-specific fatigue caused by the workouts.
Now that we better understand how the lactate shuttle works, we can design different types of lactate-shuttle training.
Threshold intervals (MCT1 focus)
Goal: improve lactate uptake and oxidation
Example (ta favorite running workout of HYROX world champion Tim Wenisch):
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6–8 × 1 km at threshold pace with 1–1.5 minutes of recovery
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Lactate is elevated but remains just below threshold (~3–5 mmol/L).
Why this works:
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prolonged exposure to sub-threshold lactate levels
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slow-twitch muscle fibers learn to burn lactate
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strong stimulus for MCT1 expression
Over-under intervals (MCT1 + MCT4)
Goal: improve lactate transport between muscle fibers
Example: an interval workout by Hidde Weersma:
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4–5× (400 m @ 3:00/km followed by 800 m @ 3:30/km – HYROX pace)
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2–3 minutes recovery between blocks
Why this works:
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lactate production followed by active clearance
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forces continuous lactate shuttling
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HYROX-specific
VO₂max-intervals (MCT4-focus)
Goal: improve lactate efflux from fast-twitch muscle fibers
Example: variations on the Norwegian 4×4 method:
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4–6 × 3–5 minutes at VO₂max pace
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Recovery: also 3–5 minutes
Why this works:
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high glycolytic stress
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high intracellular lactate and H⁺ concentration
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strong stimulus for MCT4
Sprints in aerobic training
Goal: process lactate while running
Example:
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60–90 minutes of easy endurance running
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Every 10 minutes: 20–30 seconds accelerating to anaerobic power (40–60 sec/km faster than threshold pace)
Why this works:
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lactate spikes from the surges
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immediate uptake by aerobic fibers
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low fatigue, high transfer value
Overview
| Training type | Primary MCT-effect |
|---|---|
| Threshold interval | ↑ MCT1 |
| Over-unders | ↑ MCT1 + lactate shuttle efficiency |
| VO₂max-intervals | ↑ MCT4 |
| Sprints in aerobic training | Coordination lactate shuttle |
Wrap-up
If you understand what different running workouts do physiologically, you’ll also train more effectively for HYROX.
A session I love and hate in the final weeks before a HYROX race – inspired by an Alexander Rončević lactate-shuttle interval – looks like this:
My lactate threshold is at 3:32/km.
The session:
4× (300m @3:15/km – 600 m @3:45/km – 300m @3:15/km – 600 m @3:45/km)
→ in total 1800 m over-under per block
1:30 min recovery
This training combines:
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lactate production
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lactate clearing
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running under fatigue
Exactly what you need in HYROX.
If you want to know where your personal thresholds lie, how big your aerobic engine is, and how efficiently you run, a run exercise test is a logical next step.
It forms the foundation for smarter training—and faster running in your next HYROX.
