Start conservative, finish assertive
The first third of an ultra is where disciplined fueling sets the tone. Go out with a conservative carbohydrate target—around 60 grams per hour—while you are settling into pace. Early restraint leaves room to increase intake later without overwhelming your gut. In the middle third, step up to 70–80 grams per hour if your stomach feels stable, then hold that level as fatigue builds. By the final third, focus on small, frequent doses to keep absorption steady even as your digestive system slows.
Keep intensity in check
Heart rate and fueling success are tightly linked. High spikes reduce blood flow to the gut, making even reliable foods feel heavy. Use RPE or heart rate caps on early climbs to protect your fueling plan. If you catch yourself surging, back off for two to three minutes and take a sip of carb drink; this resets both effort and intake rhythm.
Hydration that matches the course
Ultra courses swing from shaded forest to exposed ridgelines, so your hydration should adapt across segments. Aim to replace 60–90 percent of your sweat loss, not 100 percent. Overhydration can dilute sodium and bloat your stomach. If you sweat heavily, consider carrying a higher-sodium mix in one flask and plain water in the other. This lets you respond to heat without overloading sodium on cooler stretches.
Calibrating aid station refills
Print a card that lists the distance and expected time between aid stations. Convert those times to fluid needs using your sweat-rate estimates. For a 75-minute gap in warm weather, you might need 1 liter of fluid plus 800–1000 milligrams of sodium. If aid stations offer only water, pack concentrated electrolyte packets and pre-measured drink mix to hit those numbers without guesswork.
Balancing gels, drink mix, and real food
A single-source fueling plan often fails after six hours because taste fatigue hits hard. Build a rotation: gels for climbs, chewable carbs for runnable terrain, and small bites of real food when pace drops. Aim for 80 percent of calories from easy-to-digest carbs, leaving 20 percent for savory or fatty items that calm hunger. Keep fiber low; a tiny tortilla with nut butter is usually easier than a dense bar.
Mini-meals for overnight sections
During overnight racing, mood and alertness matter as much as glycogen. Schedule mini-meals—soft potatoes with salt, broth with noodles, or rice balls—every 2–3 hours. Pair each with 300–400 milliliters of warm fluid to aid digestion and help regulate core temperature. Add caffeine sparingly after midnight to avoid jitters when footing is sketchy.
Caffeine as a controlled tool
Caffeine improves perceived effort but can backfire if stacked early. Start with a small dose in hour two or three, then space subsequent doses 90–120 minutes apart. Keep total intake below 3 milligrams per kilogram to limit GI upset and rebound fatigue. If you are sensitive, rely on caffeinated gels late in the race rather than tablets; the lower dose is easier to titrate.
Managing the caffeine “ceiling”
If your heart rate feels jumpy or you get shaky hands, pause caffeine for at least an hour and focus on steady carbs plus sodium. Swapping to a lower-sweetness carb source—like a diluted mix—reduces the sensation of overload. Caffeine is a lever, not a crutch; protect sleep the night after the race by avoiding doses in the final hour unless you truly need alertness for technical terrain.
Gut-saving tactics when things go sideways
Even with careful planning, ultras deliver curveballs. Nausea often stems from cumulative intake being too sweet, too concentrated, or paired with intensity spikes. Switch to a bland carb drink at 3–4 percent concentration and sip every five minutes. If you cannot tolerate sweetness, try salted broth plus a small bite of white bread to restart digestion. Avoid chugging plain water; it dilutes sodium and can worsen sloshing.
When to use anti-nausea aids
Some runners carry ginger chews or over-the-counter motion-sickness tablets. Test these in training before trusting them on race day. If you do take them mid-race, restart fueling slowly: 20 grams of carbs over 15 minutes, then reassess. The goal is to keep calories dripping in without shocking the stomach.
Heat, cold, and altitude playbooks
In heat, prioritize sodium first, carbs second, and accept a slight drop in intake while you manage core temperature. Use ice in your hat or sleeves at aid stations to free mental bandwidth for eating. In cold conditions, bring insulated bottles so your mix does not chill your stomach; warm broth can supply both sodium and calories. At altitude, lower absolute intensity and lean on liquid carbs to reduce chewing and swallowing effort. Each of these scenarios should be mapped in your plan with specific products and quantities.
Crew and self-support logistics
Brief your crew with a checklist: the planned carb and sodium targets, flavor rotations, caffeine timing, and backup foods. Pre-pack bags for each aid station with labeled flasks and gels so swaps take seconds. If you are racing without crew, stash resupply kits in drop bags with a written script for the next segment. Simplicity wins at hour ten when your decision-making slows.
Quick checks before leaving an aid station
Run a 30-second scan: Do you have enough calories for the next segment? Are both flasks filled to the plan? Did you take your planned sodium? Have you packed any trash that could chafe? This micro-routine prevents missing a gel or leaving with an empty bottle.
Practice the exact plan
No fueling strategy counts until it survives rehearsal. Simulate race pace, terrain, and weather on your longest training runs. Use the same flavors, bottle sizes, and caffeine timing. Log how your stomach feels every hour and whether you finish with even energy. Adjust one variable per week—sodium concentration, carb per hour, caffeine spacing—so you know which change drove the result.
Recognizing when the plan is working
A good fueling plan is boring: steady mood, clear head, and legs that respond to surges late. You should still be able to chew food at hour eight, pee clear to light yellow, and hold form on descents. When those boxes stay ticked across multiple long runs, you have earned the right to trust the plan on race day.
Final reassurance
Ultra fueling is not magic; it is a series of small, repeatable behaviors. Start conservative, build intake as your gut allows, keep sodium aligned with heat, and have backup textures ready. Do the rehearsals, brief your crew, and enter the start corral knowing the bonk is not inevitable. That confidence makes every aid station a checkpoint, not a crisis.
