Trail Signal · Issue 002

Fueling above 60 g/hour: useful edge or gut bomb?

Leave with a smarter way to test high-carb fueling before your next long trail race.

Estimated read: 7 minutes

Signal Brief

Trail runners love debating shoes, poles, and vert. But many long races are decided by a quieter system: whether you can keep eating enough carbohydrate without turning your stomach into the limiter.

This week’s signal: 60 grams of carbohydrate per hour is not a magic ceiling. Higher targets can help in long mountain efforts, but only when the gut, product mix, hydration plan, and race logistics are trained together.

The Study

A 2020 Nutrients study tested carbohydrate intake during a mountain marathon in 20 elite male runners. The race included roughly 4,000 meters of cumulative slope, and runners were assigned to consume 120 g/hour, 90 g/hour, or 60 g/hour of carbohydrate. Importantly, the athletes had previously practiced nutritional and gut training.

Source: Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon

The practical signal is that higher hourly carbohydrate intake may be a real performance and recovery tool for long trail efforts, not just a cycling-lab idea. But the study also shows the boundary: small sample, elite male runners, prior gut training, and a specific mountain-marathon context.

Supporting idea: higher fueling targets usually work better when the carbohydrate mix uses more than one intestinal transport pathway, rather than simply adding more of the same sugar source.

Multiple Transportable Carbohydrates During Exercise · Superior Endurance Performance with Multiple Transportable Carbohydrates

Confidence level: Medium-high that trained higher-carb fueling can help some long-course athletes. Medium for any individual runner’s exact target.

Field Application

Do not start by chasing 120 g/hour. Start by finding your current reliable number. For one long run this week, choose a route where you can keep effort controlled and safely troubleshoot.

• If you usually take 30–40 g/hour, test 45–50 g/hour.
• If you usually take 50–60 g/hour, test 65–75 g/hour.
• If you already tolerate 75 g/hour, test whether 80–90 g/hour is actually better or just more complicated.

Track carbs/hour, fluid/hour, product mix, stomach comfort from 1–10, and late-run energy.

Gear Signal

High-carb fueling is partly a packaging problem. Precision Fuel & Hydration’s PF 90 Gel is listed as a resealable pouch with 90 g carbohydrate per pouch. Maurten’s Gel 100 is listed at 25 g carbohydrate per serving.

PF 90 source · Maurten Gel 100 source

• Large pouch: fewer wrappers and easier math, but one flavor/texture for longer.
• Small gels: more flexible, but more trash and more chances to skip fuel.
• Drink mix: efficient when drinking steadily, risky if fluid intake changes.
• Chews/real food: useful for variety, harder to chew at higher intensity.

Missed Signal

• GI symptoms are not just a “weak stomach” problem. Source
• Multiple-transportable carbs matter because the gut has transport limits. Source
• Race-day fueling is a logistics plan: packets, pockets, refills, concentration, trash, and reminders.

One Thing to Test This Week

Run one controlled long run with a written fueling target. Afterward, write the actual numbers. If your watch has splits but your fueling log is a guess, you are missing one of the most useful performance signals in trail running.

Disclosure

Trail Signal is educational, not medical advice. Product mentions are examples, not endorsements, and should be independently verified before publication. Some future links may be affiliate links. Sponsored placements will be labeled.