Trail and ultra-trail race-day fuel plan
In trail and ultra, energy depletion is what most often pulls athletes out of the race (DNF). Events over 4 hours require 60 to 90 g/h of carbohydrate, prior gut training, and a Plan B strategy for when the stomach revolts on climb 3.
Carbs per hour in ultra
For 2h30-4h events, target 60 g/h with glucose or blends. Above 2h30, move mandatorily to 60-90 g/h with a glucose+fructose blend (2:1 or 1:0.8 ratio), because pure glucose saturates the SGLT1 transporter at ~60 g/h. Elite athletes with gut training reach 100-120 g/h in trail marathons and show less muscle damage post-race (Viribay 2020, Nutrients).
Pre-race meals
Carb loading at 8-12 g/kg/day in the 24-48h before maximises glycogen. Breakfast 3h before with 1-2 g/kg of carbs (Rauh 2021 showed +8% time to exhaustion vs fasting). If the race starts in the afternoon, eat a normal breakfast at 07:30 and a pre-race lunch at T-3h. Pre-start snack (gel + 200 ml water) right before, or skip the 30-90 min window before (reactive hypoglycaemia risk, Bender 2023, EJSS).
Plan B for GI distress
In ultras, GI symptom prevalence exceeds 60%. If your stomach revolts mid-race: stop gels immediately; cut volume to 10-15 g per dose; dilute the drink further (concentrations <6% empty faster); switch to real food (banana, honey, dates); drop pace by 10-15 min to restore splanchnic blood flow (Costa 2025, Sports Med, joint position statement).
Gut training: how to train the gut for 90 g/h
4-6 week protocol. Start in your long training sessions (90+ min) with 30 g/h. Step up 10 g/h every week until you hit the race target (60, 75 or 90 g/h). Always use a glucose+fructose 2:1 blend from the start, because fructose recruits the GLUT5 transporter, complementary to glucose-SGLT1, and doubles total absorption capacity. The gut adapts both quantitatively (more transporters expressed in the mucosa) and qualitatively (fewer perceived GI symptoms). Athletes who ingest 90 g/h in race without prior gut training have DNF rates above 40% from GI causes (Costa 2025, Sports Med).
Real food vs gels in 8h+ ultras
Gels dominate easily up to 6-8 hours. After that, flavour fatigue, sweet aversion and nausea push athletes to abandon carbs altogether. Plan B: rotate real food in the second half: banana and peanut butter sandwiches, boiled potatoes with sea salt, fig newtons, warm miso soup (electrolytes + comfort), bowl of white rice with honey. Keep calorie density (~150 kcal per snack) but change texture, temperature and flavour. UTMB and Lavaredo have exactly this at aid stations from midnight onward. Trail food is not luxury, it is adherence management.