The Science Behind Your Body's Fuel Tank
Your body relies on two primary fuel sources during exercise: carbohydrates (stored as glycogen) and fats. For lower-intensity, shorter efforts, your body efficiently uses both, with a greater percentage coming from fat. However, as the duration and intensity of your run increase, your body relies more heavily on its finite glycogen reserves. For most individuals, these stores can last between 60 and 90 minutes, depending on the intensity of the effort, before becoming significantly depleted.
The Timing of Fuel Intake
For runs exceeding 60-90 minutes, supplementing your internal glycogen stores becomes essential. Waiting until you feel fatigued or 'bonk' is a mistake, as this is a sign that your energy is already critically low. Most experts recommend starting your fueling strategy within the first 30-45 minutes of a longer session and continuing with regular, smaller intakes every 20-45 minutes. Practicing this during training is crucial to teach your stomach how to digest calories while running and find a fueling rhythm that works for you.
How Much and What to Eat for a 90-Minute Run
For a 90-minute effort, the consensus suggests aiming for 30-60 grams of carbohydrates per hour, which should begin around the 30-45 minute mark. This intake will top off your blood glucose levels and delay fatigue. What you consume, however, is a matter of personal preference and tolerance. Options range from purpose-built sports nutrition products to easily digestible whole foods.
Fueling Options Comparison
| Fuel Type | Carbohydrate Source | Pros | Cons |
|---|---|---|---|
| Energy Gels | Maltodextrin, Fructose | Fast-acting, portable, pre-portioned | Can cause stomach distress, flavor fatigue |
| Energy Chews/Blocks | Sugars | Easy to chew, pre-portioned, good texture | Require more chewing than gels, can be sticky |
| Sports Drinks | Sugars, Electrolytes | Rehydrates and fuels simultaneously | Can be bulky to carry, might not provide enough carbs alone |
| Whole Foods | Banana, Dates, etc. | Natural ingredients, can be easier on the stomach | Less portable, requires chewing, can contain fiber |
The Crucial Role of Hydration
Proper hydration is directly linked to energy, endurance, and concentration. For a run over 90 minutes, plain water is not enough; you also need to replace lost electrolytes, especially sodium, through sweat. Aim to sip fluids every 15-20 minutes, totaling roughly 400-800ml per hour depending on conditions and your sweat rate. Electrolyte tablets or sports drinks can help maintain proper balance.
Practice Makes Perfect: Don't Wait for Race Day
Many runners make the mistake of waiting until a race to test their fueling and hydration strategies. Your long training runs are the perfect laboratory. Test different products and timings to see what your body tolerates best. Keeping a log can help you track what worked and what didn't. This practice is vital for avoiding surprises on race day and ensuring you can perform at your best. By training your gut, you improve its ability to absorb and utilize carbohydrates under stress, which is a major advantage during endurance events.
Creating Your 90-Minute Fueling Plan
Your personalized plan should be based on your body weight, intensity, and how you feel. A general strategy involves:
- Pre-Run Fueling: Eat a carbohydrate-rich, easy-to-digest meal 1-2 hours before the run. Examples include toast with peanut butter and banana or oatmeal with fruit.
- During the Run: Start consuming 30-60g of carbs per hour around the 45-minute mark. Break this into smaller, more frequent doses (e.g., a gel every 30 minutes).
- During the Run: Sip fluids with electrolytes every 15-20 minutes. Consider sports drinks or adding electrolyte tablets to your water.
- Post-Run Recovery: Refuel within 30-60 minutes after finishing with a mix of carbohydrates and protein to replenish glycogen and repair muscles. Chocolate milk is an excellent, readily available option.
Final Thoughts on a 90-Minute Run
Ultimately, the decision to fuel during a 90-minute run depends on the individual, but for most runners, especially those training for longer distances or running at a moderate to high intensity, fueling and hydrating proactively is the smarter choice. It's not about if you can do it without fuel, but about optimizing your performance, enhancing recovery, and making the run feel strong all the way to the finish. For further reading on fueling for longer distances, consider this resource from Runners World: What to Eat Before a Long Run to Maintain Your Energy.
Conclusion
While a 90-minute run is on the borderline for some, the evidence overwhelmingly supports the need for mid-run fueling to sustain energy, maintain performance, and prevent premature fatigue. Proactive fueling with carbohydrates and consistent hydration with electrolytes from the 45-minute mark onwards can make a significant difference. By practicing your fueling strategy during training, you ensure a smoother, stronger, and more enjoyable experience on all your long runs.
