The Critical Role of Nutrition in Ultramarathons
Completing a 100-mile race demands more than physical endurance; it requires precise nutritional preparation. Ultrarunners face unique challenges, including prolonged energy expenditure, muscle breakdown, and hydration imbalances. A well-structured nutrition plan can prevent glycogen depletion, maintain mental focus, and reduce the risk of gastrointestinal (GI) distress, ensuring athletes cross the finish line strong.
Calculating Energy Needs: Beyond Calorie Counting
Ultramarathoners burn between 700-1,000 calories per hour, depending on terrain, pace, and body weight. However, the body can absorb only 240-300 calories per hour during intense activity, creating a caloric deficit. To bridge this gap:
Calculate your Total Daily Energy Expenditure (TDEE) using fitness trackers or metabolic equations to estimate baseline needs.
Prioritize energy density in foods (e.g., high-carb fuels with electrolytes) to maximize absorption without GI strain.
Avoid drastic deficits in training to teach the body to utilize fat as fuel, preserving glycogen for critical race moments.
Macronutrients: The Building Blocks of Endurance
Carbohydrates: The Primary Fuel Source
Store 1,500-2,000 calories as glycogen in muscles and the liver. Beyond this, excess carbs convert to fat.
Race-day strategy: Consume 30-60g of carbs per hour via gels, sports drinks, or easily digestible solids. For races under 3 hours, higher glycogen stores may reduce reliance on external fuel.
Protein: Repairing the Damage
- Muscle breakdown occurs continuously during long runs. Aim for 0.25g of protein per pound of body weight hourly during races to slow degradation.
- Include branched-chain amino acids (BCAAs) in electrolyte drinks to preserve muscle tissue and delay fatigue.
Fats: The Long-Term Energy Reserve
- Fat-adapted athletes can spare glycogen by relying on fat oxidation. Train with low-carb, high-fat meals (e.g., avocado, nuts) to improve metabolic flexibility.
- During races, fats from trail-friendly options like nut butters or bacon can provide sustained energy when carbohydrate absorption becomes erratic.
Hydration and Electrolyte Balance: Staying in Equilibrium
The Science of Sweat
Sweat contains sodium, potassium, calcium, and magnesium. Replace these electrolytes to prevent cramps, hyponatremia, and fatigue:
Sodium: Aim for 500-700mg per hour, especially in hot conditions.
Potassium: Found in bananas and potatoes, it maintains nerve and muscle function.
Hydration: Drink to thirst, aiming for 16-24oz of water per hour, adjusting for heat and elevation changes.
Signs of Imbalance
Hyponatremia: Symptoms include nausea, headaches, and muscle spasms. Treat with salty snacks or IV fluids.
Dehydration: Monitor urine color and heart rate elevation-early signs of fluid deficit.
Real-Time Fueling Strategies for Race Day
Pre-Race (24-4 Hours Before)
Carbo-load: Increase carb intake to 8-10g per kilogram of body weight, paired with adequate electrolytes.
Limit fiber/fat: Reduce gut irritation risks with easily digested foods like white rice, pasta, or smoothies.
During the Race
First 60-90 minutes: Rely on body's glycogen stores; start fueling before hunger sets in.
Solid vs. liquid fuels: Rotate between gels, chews, and solid snacks to prevent taste fatigue. Pair with water to optimize absorption.
Nighttime adjustments: Cold temperatures may slow digestion; prioritize warm liquids like broth or tea.
Avoiding Common Nutritional Mistakes
Overloading on water: Dilute electrolytes by drinking beyond thirst.
Ignoring GI comfort: Test all fuels in training to avoid mid-race surprises like bloating or diarrhea.
Underestimating practice: Refining fueling habits takes months of trial and error.
Resisting salt: Salt tablets or savory snacks can prevent cramps when sweat loss is extreme.
Conclusion: Fueling as a Dynamic Process
There is no one-size-fits-all approach to ultramarathon nutrition. Successful athletes adapt their strategies based on training feedback, environmental conditions, and individual metabolism. By combining scientific principles with personalized experimentation, runners can transform nutrition from a vulnerability into a competitive advantage.