Running Refueling: When, What, and How to Fuel Your Runs

When should you refuel when running?

Refueling during a run is primarily necessary for runs lasting longer than 60-75 minutes, or for shorter, high-intensity efforts, to replenish glycogen stores and maintain blood glucose levels, thereby preventing fatigue and optimizing performance.

Understanding Energy Systems & Glycogen

To understand when to refuel, we must first grasp how your body powers movement. Running primarily relies on two main energy sources: carbohydrates (stored as glycogen in muscles and liver) and fats.

• Carbohydrates (Glycogen): Your body's preferred high-octane fuel for moderate to high-intensity exercise. Glycogen stores are limited, typically providing enough energy for 60-90 minutes of continuous moderate-intensity running. Once these stores deplete, you experience "hitting the wall" or "bonking," characterized by severe fatigue and a drastic drop in performance.
• Fats: An abundant fuel source, but less efficient for rapid energy production compared to carbohydrates. Fat metabolism becomes more prominent during lower-intensity, longer-duration activities, but it cannot fully compensate for depleted glycogen stores during higher efforts.

The goal of on-run fueling is to delay glycogen depletion and maintain stable blood sugar, ensuring a continuous supply of readily available energy for your muscles and brain.

The "When" Depends on Duration and Intensity

The necessity and timing of refueling are highly dependent on the duration and intensity of your run.

Fueling for Runs Under 60 Minutes

For most runs lasting less than 60 minutes, particularly at moderate intensities, your body's pre-existing glycogen stores are generally sufficient.

• No On-Run Fueling Needed: Unless you started with depleted glycogen stores (e.g., fasted run, multiple training sessions in a day), you typically do not need to consume carbohydrates during these shorter runs.
• Focus on Pre-Run Nutrition: Ensure you have consumed a balanced meal or snack 2-4 hours before your run, rich in complex carbohydrates, to top off glycogen stores.
• Hydration is Key: While fuel may not be necessary, consistent hydration before and during these runs is still crucial.

Fueling for Runs 60-90 Minutes

As your run approaches or exceeds the 60-minute mark, especially if the intensity is moderate to high, on-run fueling becomes increasingly beneficial.

• Consider Early Fueling: If you anticipate hitting the 60-minute mark and continuing, consider taking your first dose of fuel around 45-60 minutes into the run. This proactive approach helps maintain blood glucose before significant drops occur.
• Target 30-60g Carbs/Hour: For runs in this duration, aiming for 30-60 grams of carbohydrates per hour can help sustain energy levels.

Fueling for Runs Over 90 Minutes (Long-Distance and Marathon Training)

For long runs, half-marathons, marathons, and ultra-marathons, mid-run fueling is not just beneficial but absolutely essential to sustain performance and prevent bonking.

• Start Early and Consistently: Begin your fueling strategy around 45-60 minutes into the run. After this initial intake, aim to consume fuel every 30-45 minutes consistently throughout the remainder of your run.
• Higher Carbohydrate Intake: For these longer durations, the recommended carbohydrate intake increases, typically ranging from 30-60 grams per hour for most runners. Highly trained endurance athletes performing at high intensities may tolerate and benefit from up to 90 grams of carbohydrates per hour, often utilizing a mix of glucose and fructose to maximize absorption.
• Practice Your Strategy: Long runs are the ideal training ground to practice your race-day fueling strategy. Experiment with different types and amounts of fuel to see what your body tolerates best.

Types of Fuel for During-Run Refueling

The best on-run fuel delivers easily digestible carbohydrates quickly. Common options include:

• Sports Gels: Concentrated sources of carbohydrates, often with added electrolytes. Quick and easy to consume.
• Sports Chews/Blocks: Similar to gels but in a chewable form. Can be easier to manage for some.
• Sports Drinks: Provide carbohydrates and electrolytes. Excellent for simultaneous fueling and hydration.
• Real Food: Options like pretzels, bananas, dates, or energy bars can work, but require more chewing and can be harder to digest for some during high-intensity efforts. Choose low-fiber, low-fat options.

Focus on sources that are primarily simple sugars (glucose, maltodextrin, fructose) for rapid absorption.

Practical Strategies for On-Run Fueling

• Train Your Gut: Your digestive system is trainable. Just as you train your muscles, you must train your gut to efficiently absorb carbohydrates during exercise. Regularly practice your fueling strategy during long training runs.
• Listen to Your Body: While guidelines exist, individual needs vary. Pay attention to early signs of fatigue or hunger.
• Don't Wait Until You're Depleted: Proactive fueling is more effective than reactive fueling. By the time you feel "bonked," it's often too late to recover quickly.
• Small, Frequent Doses: It's often better to take smaller amounts of fuel more frequently than large amounts less often, as this can reduce the risk of gastrointestinal distress.
• Pair with Water: Always consume gels and chews with water to aid digestion and absorption.

Hydration: A Critical Partner to Fueling

Fueling and hydration go hand-in-hand. Dehydration can impair performance and make it difficult for your body to process consumed fuel.

• Water: Essential for all runs.
• Electrolytes: For runs over 60 minutes or in hot conditions, consuming electrolytes (sodium, potassium) is crucial to replace losses through sweat and prevent hyponatremia (low blood sodium). Sports drinks or electrolyte tablets can provide these.
• Drink to Thirst: While some advocate for scheduled drinking, listening to your body's thirst cues is a good general strategy.

Individualizing Your Fueling Strategy

No two runners are exactly alike. Factors influencing your fueling needs include:

• Metabolic Efficiency: How efficiently your body uses fat vs. carbohydrates.
• Training Status: Highly trained athletes may have better fat oxidation capabilities.
• Genetics: Individual differences in digestion and absorption.
• Environmental Conditions: Hot and humid conditions increase fluid and electrolyte needs, and can sometimes affect digestion.
• Pre-Run Nutrition: The quality and quantity of your pre-run meal significantly impact your starting glycogen levels.

Experiment during training to find what works best for your body, your pace, and your race-day conditions.

The Importance of Post-Run Recovery Fueling

While the primary question focuses on during-run fueling, it's worth noting that optimal recovery fueling (carbohydrates and protein within 30-60 minutes post-run) is critical for replenishing glycogen stores and repairing muscle tissue, preparing you for your next training session. This proactive recovery aids in starting subsequent runs with full energy reserves, potentially reducing the immediate need for early on-run fueling.

Conclusion

Strategic refueling is a cornerstone of successful endurance running. For runs under 60 minutes, focus on pre-run nutrition and hydration. For efforts beyond this, begin fueling around the 45-60 minute mark and continue consistently every 30-45 minutes, aiming for 30-60 grams of carbohydrates per hour, or more for elite athletes. Remember to train your gut, prioritize hydration, and personalize your strategy based on your unique physiological responses and the demands of your training and racing.