May 13, 2026, 2:33 pm | Read time: 5 minutes
Anyone familiar with the sports world knows: Hyrox is no joke. The competition consists of eight kilometers of running–and as if that weren’t enough, there are eight intermediate stations: exercises that demand strength, endurance, and coordination. That already sounds pretty exhausting, but for one man, it’s not enough. Professional athlete and fitness trainer Simon Gronau wants to do Hyrox for 100 days straight–one Hyrox every day. He shared how he came up with the idea in an interview with FITBOOK.
From Injury to Extreme Idea: How It All Began
FITBOOK: How did the idea for “100 Days, 100 Hyrox” come about?
Simon Gronau: “The idea came after the Hyrox World Championship in Chicago last year. Shortly after, I broke a rib in an accident and had to take a break. During this time, I reflected and realized that even a highlight like the World Championship received relatively little attention on my channels. Together with a friend from marketing, I then thought about how to think of Hyrox differently–away from a single competition, toward an ongoing story. That’s how the idea was born: 100 Days, 100 Hyrox. It was only in the next step that it became an official record attempt.”
Why exactly 100 days?
“The number originally came from me. The Record Institute for Germany then set it as the minimum requirement for the world record.”
“It’s Not About Achieving Best Times Every Day”
How are you strategically approaching the 100 days?
“I’m starting consciously controlled and trying to put my ego aside. It’s not about achieving best times every day, but about enduring the series. In the first seven to ten days, I’ll observe how my body reacts and then adjust accordingly.”
What did a typical training week look like?
“I had about eleven to thirteen sessions per week. These included basic endurance, strength training for the upper and lower body, core stability, as well as intensive sessions to improve the lactate threshold and maximum oxygen uptake. This was supplemented by active recovery, such as light cycling. One day per week was completely free.”
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“I Find Burpees the Most Challenging”
What have you specifically changed in your training?
“Mainly the volume. I trained about two and a half to three hours daily–a mix of running, strength training, and endurance sessions. The goal was to get the body used to constant stress.”
Are there disciplines you excel at–or not at all?
“I’m strong in running, on the ergometers, and with lunges. Sled pulling and pushing also suit me due to my body weight. I find burpees the most challenging, especially over the distance.”
Do you have particular respect for certain exercises?
“Less for individual exercises than for the sum. Hyrox is very lower-body intensive, and the repeated stress will become noticeable over time.”
Five Months of Preparation for 100 Days of Continuous Stress
How long did you prepare for this?
“About five months specifically. I had already trained a lot for Hyrox before, but more with a focus on individual competitions. This project is different–it’s more in the direction of ultra-endurance.”
How do you ensure you can deliver this performance daily?
“The key is recovery. It starts with warming up, includes adequate fluid and nutrient intake during the competition, and extends to immediate recovery afterward, such as light cycling or cold applications. Sleep is also crucial–I plan for eight to eight and a half hours per night. Additionally, I try to keep stress in everyday life as low as possible.”
Have you already noticed a mental change?
“Yes, very much. I already feel how much it inspires me for my future life to know that you can get through some pain if you keep a very specific goal in mind every day. At the same time, I am very grateful for the routine and performance capability I have built up over the past years.”
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“This Is Not a Health Project, but an Extreme Strain on the Body”
How was the project medically evaluated?
“I underwent comprehensive examinations beforehand, including a performance diagnosis and a full-body MRI. The results were consistently positive, and I got the green light. Still, it’s clear: This is not a health project, but an extreme strain on the body.”
First Interim Conclusion After 46 Days
46 days are over–what’s your conclusion?
“It’s always a bit of an up and down. Right now, it’s a little up again, but the days before were definitely a significant down since I got the diagnosis of my injury–or rather, my injuries. At the moment, we’re doing everything we can to get it back on track and ensure the injuries don’t get worse and heal well in everyday life. I currently have an injury in my lower leg and midfoot. But I’m caught in a dilemma where I don’t want to promote sports with an injury–at the same time, I want to hold on to my dream and my world record, and my team and I are doing everything we can to keep going.”
What bothers you the most, physically speaking?
“I think I underestimated the stress in several areas, which has accumulated over these many days. I have good fitness, but the race’s stress takes a structural toll on the body. However, the focus remains forward, and progress continues. I’ve learned a lot from the project, which goes far beyond the athletic aspect. I’m very, very optimistic, and for me, it feels like day 1 again. I’m giving it my all, and now recovery is more crucial than ever. The goal is to keep the overload so low that the strain doesn’t progress further.”
And what do you expect after the 100 days?
“Honestly, I’m very curious about how my body will react–whether the project will make me stronger or more fatigued. Afterward, I’m especially looking forward to private moments: a wedding among friends and time with my family. That will be a nice conclusion.”