Most athletes don’t underperform because they lack fitness. They underperform because they don’t fuel for the effort they’re trying to sustain.
This isn’t about eating more. It’s about understanding how much your body can actually absorb, oxidize, and use under race conditions.
For years, many athletes have treated fueling as a secondary detail — something to think about after training, pacing, and race strategy. But once intensity rises and fatigue starts to build, fueling becomes part of the performance equation itself.
What Happens When You Actually Test Fueling?
To move beyond guesswork, controlled laboratory testing has explored how different carbohydrate intake strategies impact endurance performance. Across multiple prolonged treadmill efforts, three intake levels were compared: 60g, 90g, and 120g of carbohydrates per hour.
This wasn’t just about performance output. The study focused on what actually drives endurance performance — measuring heart rate, blood lactate, oxygen consumption, and exogenous carbohydrate oxidation. In other words, not what athletes think they’re using, but what their body is actually able to burn.
In practice, this means moving beyond perception. What feels sustainable is not always what is physiologically optimal, especially when fatigue accumulates over time.
More Carbs Didn’t Mean More Stress — It Meant More Control
The highest intake — 120g of carbohydrates per hour — produced the most stable physiological response. This didn’t mean the effort felt easier in absolute terms, but that the system itself was better supported.
With higher carbohydrate intake, athletes experienced lower perceived effort, more consistent energy levels, better fluid retention, reduced body mass loss, and a delayed reliance on fat metabolism. At lower intake levels, the opposite pattern emerged: earlier fatigue, greater physiological strain, and a faster decline in efficiency.
What this highlights is not comfort, but control — the ability to maintain output without the system breaking down as fatigue builds.
Why This Matters (And Why Most Athletes Get It Wrong)
At race intensity, your body is limited by how much oxygen it can use. Carbohydrates produce more energy per litre of oxygen than fat, making them the more efficient fuel as intensity increases.
The implication is simple but often overlooked: the more you rely on carbohydrates, the more efficient your engine becomes at the same effort. When carbohydrate intake is too low, the body is forced to shift earlier toward fat metabolism — a slower and less efficient process.
At low intensity, this isn’t a problem. At race pace, however, it becomes a limiting factor. In practical terms, this means you are working harder to produce the same output, and fatigue arrives sooner.
60g vs 120g — What Actually Changes
The difference between low and high carbohydrate intake is not theoretical — it shows up directly in performance. At 60g per hour, athletes tend to experience earlier fatigue onset, higher cardiovascular and metabolic strain, greater fluid loss, and an earlier shift toward fat oxidation.
At 120g per hour, the system remains more stable: output is easier to sustain, fatigue is delayed, hydration status improves, and energy production becomes more efficient over time. This isn’t about feeling better — it’s about maintaining performance when fatigue starts to build.
Why 120g Per Hour Is Even Possible
For years, carbohydrate recommendations for endurance athletes were capped around 60g per hour. Anything beyond that was assumed to cause digestive issues or simply go unused. What changed wasn’t just strategy — it was understanding.
The human body can absorb more carbohydrates when multiple transport pathways are used. Combining different carbohydrate sources such as glucose and fructose allows for higher total intake, as they are absorbed via separate intestinal transporters.
This is why modern fueling strategies often use mixed carbohydrate formulas, enabling athletes to reach intakes of 90g, 100g, or even 120g per hour. But capacity alone isn’t enough — the system also needs to adapt.
Can Everyone Use 120g of Carbs Per Hour?
Short answer: no.
High carbohydrate intake isn’t just about what you consume — it’s about what your body can tolerate and absorb under stress. This is where most athletes misunderstand the concept.
Fueling at 100g+ per hour is not something you “try” on race day. It is something you build toward over time. Just like your aerobic system adapts to training stress, your gut adapts to nutritional load.
Regular exposure to higher carbohydrate intake during training can improve gastric emptying, absorption rates, and tolerance. This depends on multiple factors, including gut training, carbohydrate composition (typically glucose and fructose blends), and feeding strategy (timing, frequency, and consistency).
Without preparation, high intake can lead to gastrointestinal distress, which will immediately compromise performance. This is why fueling should be trained, not improvised.
That said, this doesn’t mean one exact number applies to every athlete. Individual tolerance, event duration, intensity, and training background all influence how much carbohydrate can be used effectively.
What This Means for Hybrid Athletes
This isn’t just relevant for marathon runners. In hybrid racing, the demands are even more complex, with repeated high-intensity efforts, constant transitions between modalities, elevated lactate levels, and accumulated muscular fatigue.
All of this increases carbohydrate demand. Unlike steady-state endurance events, hybrid racing combines metabolic stress with muscular fatigue, which amplifies the importance of maintaining energy availability throughout the race.
If you underfuel, you don’t just feel worse — you lose the ability to maintain pace under fatigue. And that’s where races are decided.
Where Most Athletes Go Wrong
The biggest mistake isn’t undertraining. It’s underfueling relative to the intensity of the effort. Many athletes follow general guidelines without adjusting for race demands, duration, or intensity.
Others avoid higher carbohydrate intake due to fear of discomfort, without ever training their system to handle it. The result is predictable: performance drops not because of lack of fitness, but because the body cannot sustain the required output.
In endurance and hybrid racing, this becomes most visible in the later stages — when fueling strategy either supports performance or exposes its limitations.
What This Looks Like in Practice
For most athletes, the takeaway is not that 120g per hour is automatically the right target. The real takeaway is that fueling should match the demands of the effort.
Shorter or lower-intensity sessions may not require aggressive carbohydrate intake. But as duration, pace, and metabolic stress increase, underfueling becomes more costly.
That means race-day fueling should not be based on habit or convenience. It should be built around the intensity of the event, tested in training, and adjusted to what the athlete can actually tolerate.
In practice, this means:
- Train your fueling like you train your engine — don’t wait for race day to test higher carbohydrate intake.
- Start with a baseline (60–90g/hour) and progressively increase if performance and digestion allow.
- Match intake to session demands — easy sessions don’t need aggressive fueling, but race-pace and long efforts do.
- Use simple, repeatable sources (gels, drink mixes, easily digestible carbs) to reduce variability.
- Pay attention to tolerance, not just targets — what you can absorb under fatigue matters more than theoretical numbers.
- Rehearse race conditions — timing, format, and intake strategy should feel automatic before competition.
Because in the end, fueling isn’t just about energy intake. It’s about maintaining output when fatigue starts to dictate decisions.
Practical Takeaways
- Most athletes underfuel relative to race demands
- 60g/hour may be insufficient for high-intensity efforts
- 90–120g/hour can improve performance — if trained properly
- Fueling strategy should be tested before race day
Fueling Is a Performance Variable
You don’t rise to your fitness on race day. You drop to the level your system can sustain — and fueling is part of that system.
Not planned means not optimized. And what’s not optimized is performance left on the table.
Performance is not just built in training. It is revealed — or limited — by how well your system is supported under stress.
You don’t need more fitness. You need access to the fitness you’ve already built.
And that depends on how you fuel.
If you want to go deeper into how to structure that system — not just for race day, but across your entire training week — the full breakdown is here:
Structuring Macros for Hybrid Performance
Fueling is not support work. It is race execution.
Be bold. Be BADDAZZ. 🖤
