Issue #6: The First HYROX Study

✍️ Author’s Note

Welcome to this edition of the Threshold Lab newsletter! I’m Stephen Pelkofer, an experienced HYROX athlete with a men’s pro personal best of 59:41 and men’s pro doubles best of 51:39. If you want to learn about my story and how I got here, check out this Instagram post here.

The goal of this newsletter each week is to pick a training topic related to running or HYROX, do deep research into it, and provide actionable protocols that the reader can take away and apply to their training immediately. Let me read the research, listen to the experts on podcasts and youtube, and then give you the tools to make it work for you.

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👨‍💻 Introduction

Topic: The First HYROX Study

If you’ve ever put yourself through a HYROX race, you know that it’s a unique beast. Eight 1-kilometer runs with functional exercises in between and a brutal 100 wall-ball finish all add up to an intense endurance challenge. The sport is still very new, which means there is basically no research on the competition or training methodologies.

In March 2025, the first paper that I have seen on HYROX performance was published by a group of researches in Germany: Acute physiological responses and performance determinants in HYROX© – a new running-focused high intensity functional fitness trend (Brandt, Ebel, Lebahn, Schmidt, 2025). I’m going to do a deep dive into this paper today and see what insights we should and shouldn’t take away from it.

⚡️ Fast Finds for the busy reader

• Endurance training > strength training → HYROX is an endurance event and your training should reflect this

• Blood lactate levels elevate once you hit the ski-erg, and remain elevated for the entire race duration

• Muscular endurance training > max strength training

🔬 Deep Dive

This first scientific look at HYROX rounded up 11 athletes that had completed at least one real HYROX race and put them through a full race simulation in a gym style setting (treadmills were used for the runs). The researchers tracked the following metrics during the simulation: heart rate, blood lactate levels, and the athletes’ own perceived exertion at every leg of the race. Before the simulation (2-14 days before), they also took some baseline measurements like VO₂max, grip strength, body composition, and training history (endurance vs resistance). The athletes were all instructed to not do any intense exercise in the 48 hours leading up to the simulation.

The first and biggest callout I want to make: A sample size of 11 is extremely small. Making broad generalizations from this is not recommended, but there are still interesting data points in here to look at. The researchers did a phenomenal job for this first crack at getting some scientific data on the sport. In the future, I would love to see larger samples and a study that is entirely made up of elite athletes that are at the top end of the sport.

Sample Callouts

• The average finish time here was 86 min; the fastest was 75 min; the slowest was 109 min

• Sample size: 8 men, 3 women

• Median age of 33, min of 23, max of 43

• Median VO₂max of 51, min of 46.6, max of 72 (definitely above average compared to general population)

The graph below is, to me, the most interesting data in the paper. These are averages from the group (which in all honesty is not ideal), but this would be a great chart to have for yourself from a HYROX simulation. The blood lactate levels seem to spike at the ski-erg and stay elevated for the entirety of the race, and then spike to the highest peak during wallballs. I think this is a good start to provide evidence that accumulating training time at lactate threshold is the best bang for your buck training. The rate of perceived exertion scores (RPE) are highest at burpee broad jumps and wallballs – this is not surprising to anyone that has raced before. Heart rate immediately elevates and stays there for the entire race (again, not that surprising).

An interesting takeaway for me is that the authors noted both heart rate and blood lactate levels were higher on the stations compared to the runs. I would want to see more data on this this and see if burpee broad jumps and wallballs are skewing it, but it is still good insight. It would be insightful to see what an Elite 15 athlete looks like in this chart.

The authors note that the strongest correlations with finishing times were VO₂max, endurance training volume, and body fat percentage. They call out that this race relies on both aerobic and anaerobic metabolic pathways and they even suggest that once strength and power exceed a certain level, there might be diminishing returns. Athletes should instead focus on improving muscular endurance to sustain repeated high intensity efforts. The sample size is so small but I do think the authors are spot on with the recommendations. It’s becoming more and more obvious that endurance training should be the focus for almost anyone competing in this sport and that the max strength requirements are pretty low, even at the pro weights.

There is one final passage I want to highlight from the paper before we go into the lab notes. I’m just going to copy the whole text in because I think it is so relevant for HYROX training:

Time for the lab notes ⬇️

🧪 Lab Notes

In every issue of this newsletter, the “Lab Notes” are going to be the protocols that you can apply to your training and routine right away. The goal of this section is to translate the science into actionable steps for the reader, whether you’re a recreational runner/HYROX competitor, or someone pushing the limits of their peak potential.

• Build the engine

  • Aerobic development should be the number one priority for pretty much every HYROX athlete until you reach a certain time domain (probably under 70 minutes)

  • Don’t be fooled by the sleds, lunges, and wallballs → this is primarily an endurance event

  • Become a monster at running, the rower, and the ski erg and you already have 10/16 of the race covered

• Muscular endurance > max strength

  • Hopefully this can be validated with more data eventually, but it is highly likely that max strength numbers in compound lifts don’t mean much for HYROX performance once minimum standards are met

  • Training for muscular endurance improvements and the ability to sustain power over long periods of time should be the focus of resistance training

• Practice transitions and technique under fatigue

  • If there is a skill set for HYROX, it is the ability to perform under fatigue

  • Practice the demands of the race without just doing HYROX simulations

    • Interval training that includes stations, running, and rest

    • Running with perfect form and optimal run cadence during HYROX specific sessions

  • Fatigue can mean having to run when your heart rate is already elevated, or if your legs/arms are on fire from intense station work

  • With my 1:1 caching clients, I put a large emphasis on this type of training, specifically when an athlete is in a race prep period

That’s it for this edition of the Threshold Lab. If you enjoyed this and found it useful, please share it with a friend!

What I Read and Researched for this Issue

• [1] Brandt T, Ebel C, Lebahn C, Schmidt A. Acute physiological responses and performance determinants in Hyrox© - a new running-focused high intensity functional fitness trend. Front Physiol. 2025 Mar 31;16:1519240. doi: 10.3389/fphys.2025.1519240. PMID: 40230601; PMCID: PMC11994925.