There is a pattern that repeats itself almost every time a triathlete turns up to their first Hyrox event. They have trained hard. They have the running base, the gym confidence, and probably a decent understanding of how to fuel a long endurance effort. What they have not done is rethink any of that for a sport that asks something quite different of the body.

Hyrox is not a long, steady-state effort. It is a sequence of high-intensity, repeated anaerobic bouts punctuated by running. The physiology is different. The fuelling demands are different. And the window for getting nutrition wrong is much smaller than in triathlon or marathon racing.

Dr Kelsie Johnson is a sports nutritionist and hybrid athlete coach who works predominantly with Hyrox and hybrid athletes. She joined the podcast this week, and what struck me most from our conversation was how simple the core principles actually are and how consistently athletes ignore them.

You can listen to the episode here: Hyrox, hybrid athletes and the nutrition mistakes costing you the race ​

Carbohydrate is not optional

The biggest nutritional gap Kelsie sees across her client base is not protein, and it is not hydration. It is carbohydrate periodisation around training. Most athletes understand the role of protein by now. What they are not doing is adjusting their carbohydrate intake to match the specific demands of each session they complete.

If you are heading into a ninety-minute Hyrox class, you need carbohydrates before, during, and after. It sounds obvious. In practice, most people eat whatever they usually eat and hope for the best. That approach works until it doesn't, and usually it stops working around week three of a serious training block, when cumulative under-fuelling starts to show up as fatigue, poor sessions, and that inexplicable feeling of running on empty when nothing obvious has changed.

The interference effect is real, but manageable

For triathletes considering Hyrox, or hybrid athletes trying to build both strength and endurance simultaneously, there is something worth understanding called the interference effect. Strength training and endurance training trigger different adaptive pathways in the body. When you combine both in the same block without thinking about the order or timing of sessions, those pathways can compete rather than complement each other.

The solution is not to avoid doing both. It is to be deliberate about sequencing. Kelsie works with her athletes to plan the week so that strength and endurance sessions are positioned to reinforce each other rather than undermine recovery. Fatigue management becomes as important as the sessions themselves. If you are heading into a quality run on legs already wrecked from a heavy strength session, you are training the wrong system at the wrong time.

Fuelling during the race itself

One of the more practical insights from our conversation was around race-day fuelling strategy, and specifically when to take on fuel during a Hyrox event. The intensity of the race makes eating feel almost impossible, but carbohydrate availability is critical throughout. The row and the section immediately following the burpees tend to be the most practical points to consume a gel. The row is the only moment in the race where you are seated. Coming out of the burpees, the first half lap of running gives a small window to stomach something before the next station.

Elite athletes plan this deliberately. Most amateur athletes do not plan it at all.=

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​Nothing new on race day

Kelsie's three non-negotiable principles for anyone new to Hyrox are these:

First, fuel for the work you are about to do. Carbohydrate periodisation around training is the single biggest lever most athletes are not pulling.

Second, plan your carbohydrate loading in the one to two days before the event. You do not need the full ten grams per kilo that a long-course triathlete might use, but a higher carbohydrate day in the build-up matters.

Third, and this one is not negotiable: nothing new on race day. Practice your nutrition strategy in training. Know what agrees with your stomach. Know when you are going to take your gel and how you are going to carry it.

What this looks like in the real world

In thirty years of coaching, I have watched athletes spend enormous amounts of time, money, and energy on training and then treat nutrition as the bit they will sort out later. Kelsie put it well when she said that if you are putting that much effort into your training, the return on getting your nutrition right is second to none. It is the variable that most people are leaving on the table.

The basics are not complicated. Fuel before. Fuel during if the session is intense enough to warrant it. Recover properly afterwards. Match your carbohydrate intake to the demands of the work, not to a fixed daily number that never changes. Do this consistently, and the training you are already doing will produce better results.

Hyrox rewards people who are strong, fit, and prepared. Preparation includes what you put in your body before you even walk through the door.

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​KEY TAKEAWAYS

• Carbohydrate periodisation - matching your carb intake to the specific demands of each session is the most common nutritional gap in Hyrox and hybrid athletes.
• The interference effect between strength and endurance training is real, but it is manageable with deliberate session sequencing and proper recovery nutrition.
• Plan your race-day fuelling strategy in advance: know your gel timing, how you will carry it, and practise it in training. Nothing new on race day.

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If you are training for Hyrox or making the shift from triathlon to hybrid sport, the SWAT programme gives you the structure to build durability across both strength and endurance without one undermining the other. Find out more at by clicking the link below:

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Thanks for being part of the tribe. I’m here to help you stay Battle Ready! Simon