Hitting the wall isn’t just bad luck—it’s biology. Once the body burns through its limited carbohydrate stores (glycogen), pace inevitably drops. For most runners, that energy reserve lasts only 90–120 minutes at moderate effort, and even less if running at higher intensities. The good news? Strategic mid-race fueling can delay that crash and keep performance steady.
The 90-Gram Debate
For many years, 60 grams of carbohydrates per hour was considered the benchmark for endurance events lasting three hours or more. Newer research shows that athletes can absorb more—up to 90 grams per hour—by combining two types of carbohydrate: glucose (up to 60g/hour) and fructose (up to 30g/hour). This “multiple transportable carbs” approach helps maintain pace for longer periods.
However, 90g/hour isn’t necessary for everyone. Individual targets depend on pace, event length, and gut tolerance. While elite athletes may benefit from higher amounts, 60–75g/hour is a more realistic range for many recreational runners.
Practical Considerations
Reaching 90g/hour can mean taking four gels every hour, which may be logistically and physically challenging. Using larger, high-carb gels or carbohydrate drinks can help reduce the amount carried. Training with products available on-course can also make fueling easier during a race.
Timing matters. Starting to consume carbohydrates within 30–45 minutes of the race start is generally more effective than waiting until fatigue sets in.
Cyclists vs. Runners
Ultra-endurance cyclists sometimes aim for 100–120g/hour, but this isn’t directly applicable to running. Cycling is less jarring on the digestive system, while running increases the likelihood of gastrointestinal discomfort. For runners, absorption limits and gut comfort are key considerations.
Gut Training Is Essential
Gastrointestinal distress is often the result of an untrained gut. A gradual approach—starting with 40g/hour in training and increasing over time—can improve tolerance. Observational evidence suggests that some athletes perform best at slightly lower targets, around 70–80g/hour, though research on optimal intake for different populations is still developing.
Gels, Drinks, or Real Food?
Carbohydrate drinks provide energy, hydration, and electrolytes in one, which can reduce GI issues, especially in hot conditions. Real-food options such as jelly babies (about 6g carbs each) or dates may work well in lower-intensity or off-road events. For faster racing, sports nutrition products are often more practical.
Don’t Get Hung Up on the Numbers
Consistently hitting 60g/hour is a solid goal for most runners. Exceeding this can be beneficial if tolerated, but missing a serving won’t ruin a race. The most important step is to practice fueling in training so there are no surprises on race day.
Pro tip: Mid-race fueling isn’t only about performance—it can also speed recovery and reduce muscle damage, especially in demanding events.
Race Fueling Cheat Sheet
| Race Length | Carb Target | Example Fuel |
| < 90 mins | None or light fuel | 1–2 small gels or carb drink sip |
| Half marathon (1.5–3 hrs) | 40–60g/hour | 1 gel every 20–30 mins |
| Marathon (3–5 hrs) | 60–75g/hour | 1–1.5 gels every 20 mins; mix gels & drinks |
| Ultra (5+ hrs) | 60–90g/hour* | Combination of gels, carb drinks, and real food |
*Higher targets (75–90g) require gut training.
Quick tips:
- Start fueling within 30–45 minutes of race start
- Use products tested in training
- Mix glucose + fructose sources for better absorption
- Carb drinks can help meet targets while hydrating
Bibliography
- Jeukendrup, A.E. (2014). Carbohydrate intake during exercise and performance. Nutrition, 30(7-8), 763–768.
- Stellingwerff, T., & Cox, G.R. (2014). Systematic review: Carbohydrate supplementation on exercise performance or capacity in mixed-sex studies. Sports Medicine, 44(1), 105–123.
- Rowlands, D.S., & Houltham, S.D. (2017). Multiple transportable carbohydrates during exercise: Current limitations and directions for future research. Sports Medicine, 47(S1), 107–115.
- Burke, L.M., et al. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(S1), S17–S27.
