By late July, the long run is the biggest workout of your week, and it is only getting longer. For fall marathoners, that is exactly when fueling stops being optional. Somewhere past two hours, your body starts running low on the fuel it likes best, and once that tank is empty, no amount of summer fitness will save the pace. The good news: the long run is also the perfect place to practice never letting it get there.
Fueling is the most under-trained skill in marathoning. Runners will nail every interval and never once rehearse eating on the move, then wonder why mile 22 feels like walking through wet cement. It does not have to. Fueling is learnable, and the long run is your classroom.
Why the long run needs fuel
Your body stores carbohydrate as glycogen in your muscles and liver, and that store is small: enough for roughly 90 minutes to two hours of hard running before it runs dangerously low. Hit empty and you experience what runners call bonking or hitting the wall - the sudden, full-body shutdown that turns goal pace into survival shuffle. It is not weakness. It is chemistry.
Taking in carbohydrate while you run solves it two ways. It spares your own glycogen by giving your muscles an outside fuel source, and it keeps your blood sugar steady, which protects both your legs and your focus. Do it well and you arrive at the final miles with fuel in the tank and a clear head instead of a flashing empty light.
Spare Your Glycogen
Carbs taken on the run give your muscles fuel from outside, so your limited glycogen stores stretch deep into the final miles instead of running dry at mile 20.
Steady Blood Sugar
A regular trickle of carbohydrate keeps blood glucose stable, which holds your pace and, just as important, keeps your head in the race when fatigue starts talking.
A Trainable Gut
Eating at effort is a skill your stomach adapts to. Every fueled long run teaches your gut to absorb more with less distress, so race-day nutrition becomes routine.
There is a bonus most runners miss: fueling well also speeds recovery. Finish a long run less depleted and you bounce back faster, which means the next quality session lands on fresher legs. Good fueling compounds.
When to start: fuel before you're empty
The single most common mistake is waiting. Carbohydrate takes 15 to 30 minutes to digest and reach your muscles, so if you fuel only once you feel low, you are already behind and spend the rest of the run chasing a deficit you will never close.
Instead, fuel early and on a schedule. For any long run over about 75 to 90 minutes, take your first carbs within the first 30 to 45 minutes, while you still feel great, and then keep taking them every 30 to 45 minutes for the rest of the run. Think of it as topping off a full tank, not refilling an empty one. Set a watch alarm if you have to. On the long run, the clock decides when you eat, not your stomach.
How much: the carbohydrate numbers
Here is where runners either overthink it or ignore it entirely. The targets are simpler than they sound:
- Runs of 1 to 2.5 hours: aim for 30 to 60 grams of carbohydrate per hour. A typical gel holds 22 to 30 grams, so one gel every 30 to 40 minutes lands you right in the zone.
- Your longest runs and the marathon itself: work toward 60 to 90 grams per hour. That is a real jump, and most runners need several weeks to get there comfortably.
- Going high needs a blend: your gut can only absorb so much of one sugar at a time. To take in more than about 60 grams per hour without a rebellion, use products that combine glucose and fructose (often labeled 2:1), because the two are absorbed by separate pathways.
- Count your drinks too: sports drink, chews, and gels all add up. A bottle of sports drink might carry 30 to 40 grams on its own, so tally everything, not just the gels.
You do not have to hit the top of the range to benefit, and more is not automatically better. Find the number your stomach tolerates at pace, then nudge it up as the weeks go on.
Train your gut like a muscle
The reason race-day stomach disasters happen is almost never the product. It is that the gut was never trained to handle fuel at race intensity. Blood flow shifts away from your stomach when you run hard, and a stomach that only ever practices at easy pace has no idea what to do with a gel at marathon effort.
The fix is exposure. Your intestines actually upregulate their sugar transporters when you fuel regularly, meaning you absorb more, with less nausea, the more you practice. So treat it like training: start at the low end of your carb target, add a little every couple of weeks, and above all, practice fueling during the harder parts of your long runs, not only the easy warm-up miles. By your peak weeks, taking a gel at goal pace should feel automatic.
Hydration and sodium in the summer heat
July and August fueling is not just about carbs. Heat drives up your sweat rate, and with it your losses of fluid and sodium, both of which sink performance late in a run.
Drink to thirst. For most runners in the heat that works out to somewhere around 0.4 to 0.8 liters per hour, but sweat rates vary enormously. Learn yours by weighing yourself before and after a long run: every pound lost is roughly a pint of fluid you did not replace. The goal is to finish only slightly down, not bone dry - and not, at the other extreme, heavier than you started. Overdrinking plain water can dilute your blood sodium to dangerous levels, so more is not safer.
Replace sodium when it is hot or when you are a salty sweater (white streaks on your kit are the tell). Roughly 300 to 700 milligrams of sodium per hour, from a sports drink, salt tabs, or gels that include sodium, helps you hold onto fluid and keeps cramps and that late-run fog at bay. Plain water alone on a long, hot run is one of the most common reasons a strong runner falls apart in the last 30 minutes.
Rehearse it exactly
The long run is a dress rehearsal, and that includes the fuel. Same brand, same flavor, same timing, same fluids, same way of carrying it that you plan to use on race day. Race morning is the worst possible time to discover that a certain gel turns your stomach or that your handheld sloshes for 26 miles.
Two more pieces to practice while you are at it. Your pre-run meal - a carb-rich breakfast two to three hours before - is a rehearsal for your race-morning routine, so use it. And if you plan to race with caffeine, which many gels contain, test your tolerance on training runs first rather than gambling on it cold. By your final few long runs, none of this should be an experiment. It should be a routine you could run in your sleep.
The mistakes that cause the wall
Almost every fueling disaster traces back to the same short list. Starting too late, so you spend the run chasing a deficit. Taking in too little total carbohydrate across the run. Trying something new on race day that your gut has never seen. Practicing only at easy effort, so your stomach is unprepared for fuel at race pace. And ignoring heat and sodium, then wondering why the last few miles unravel. Notice the theme: none of these are fitness problems. They are rehearsal problems, and rehearsal is exactly what the long run is for.
Where NXT RUN comes in
Fueling is a skill, and skills need the right sessions to practice on. That is where PACE Create earns its keep: tell it the long run you want - a steady two-hour build, or 16 miles with the last 6 at goal pace - and it builds the workout, sets your paces, and drops it into your plan. Those goal-pace finishing miles are your fueling laboratory, a realistic window to practice taking carbs at race effort, and the full structured session syncs to your watch so the workout and your fuel schedule line up.
Your plan handles the bigger picture too. As the weeks pass, it ramps your long runs at a rate your body and your gut can actually absorb, so the fueling demand grows step by step instead of all at once. You show up to race day with the engine, the pace, and a nutrition plan you have already run a dozen times. That is how the wall stays a stranger.