Fueling Strategies for Endurance Events That Actually Hold Up

Most endurance athletes have a fueling horror story. A bonk at mile 18. A stomach that gave out mid-race. A “why did that happen, I trained so well” moment that usually traces back to fueling, not fitness. Here’s how to build a strategy that doesn’t fall apart when it matters most.

Pre-Race Fueling

The days leading into a race are about topping off glycogen stores without introducing anything new to your gut. Carb intake typically increases in the final 1-3 days pre-race, paired with reduced training volume so the extra fuel actually gets stored rather than burned off. Race morning should repeat whatever’s already been tested in training, timed the same way, down to the specific foods.

In-Race Carb Intake Targets

For efforts beyond roughly 60-90 minutes, carbohydrate intake during the race matters. A common target range is 30-60g of carbohydrate per hour, though well-trained athletes can sometimes tolerate more with practice. The specific number matters less than testing it extensively beforehand — race day is not the time to find out your gut can’t handle a new gel or drink mix.

Hydration and Electrolyte Strategy

Fluid and electrolyte needs vary enormously by athlete, climate, and effort intensity, which is exactly why a generic “drink X ounces per hour” rule tends to fail people. A sweat rate test done in training conditions similar to race day gives a far more accurate target than any blanket recommendation, and it should factor in sodium replacement, not just fluid volume.

Common Mistakes That Cause GI Distress or Bonking

The two biggest culprits: trying something new on race day instead of anything tested in training, and under-fueling early in a race because things feel fine early, then trying to catch up once symptoms of low fuel are already showing. Both are preventable with a tested, practiced strategy locked in well before race week.

Get the Full HYROX Nutrition Guide

Want the detailed, race-day version of this strategy? See the HYROX Nutrition Guide for a step-by-step breakdown of pre-race, in-race, and recovery fueling built specifically around the demands of the event.