Race day fueling gets a lot of attention. Pre-race nutrition, recovery windows, electrolyte timing — Wall & Wire has covered all of it. But there’s a gap in most OCR athletes’ nutrition planning that shows up not on race day but on the hard training days in between: the long, multi-hour sessions where you’re running trails, doing obstacle circuits, carrying sandbags up hills, and expecting your body to keep performing for two, three, or four hours without a formal pit stop.
Fueling during training — specifically long OCR-specific training blocks — is different from marathon fueling, different from gym nutrition, and different from anything race-day guides are designed to address. It has its own complications, its own failure modes, and for athletes who’ve been glossing over it, fixing it often produces some of the most immediate performance gains they’ve ever felt.
Why OCR Training Is a Unique Fueling Problem
The standard endurance fueling advice — take in 30 to 60 grams of carbohydrate per hour after the first hour of exercise — is a reasonable baseline. But OCR training layers on complications that pure running doesn’t have.
First, there’s the effort variability. A four-hour trail run has a relatively predictable metabolic demand. A four-hour OCR training session is a series of high-intensity bursts — grip work, carries, explosive climbs, obstacle simulations — separated by lower-intensity movement. Your glycogen burn rate spikes and drops unpredictably. Athletes who try to fuel these sessions the same way they fuel a long slow run almost always underperform in the second half, not because they’re undertrained but because they’re underfueled at the wrong moments.
Second, there’s the hand problem. OCR athletes spend significant portions of long training sessions with wet, muddy, or chalked hands. Accessing a gel in a shorts pocket when your hands are slick with grip chalk or creek water is a practical obstacle that most nutrition guides completely ignore. Athletes who haven’t practiced their intra-session fueling mechanics — how they carry, access, and consume nutrition during an actual training block — often skip feedings entirely because it’s inconvenient. That’s a training error with real consequences.
Third, obstacle-heavy training can suppress appetite and delay hunger signals in ways that steady cardio doesn’t. High-intensity work elevates adrenaline, which blunts hunger. Athletes routinely go two to three hours into hard OCR training without feeling hungry at all — and then hit a wall so hard they can’t finish the session effectively. By the time hunger appears, you’re already behind.
What to Eat and When
The mechanics are straightforward even if the application is messy. For sessions up to ninety minutes, most athletes at moderate intensity don’t need intra-session carbohydrates — a solid pre-session meal handles it. For sessions approaching two hours or beyond, especially high-intensity OCR-specific work, the intra-session window becomes important.
Target 30 to 45 grams of carbohydrate per hour starting around the 45-to-60-minute mark — not the 90-minute mark that some endurance guides suggest. OCR training burns hotter than steady-state cardio, and waiting too long to start feeding creates a deficit you’ll spend the back half of the session chasing. Easy carbohydrate sources — gels, chews, banana pieces, rice balls, even sports drink — all work. The format matters less than consistency.
Protein during training sessions is less critical for sessions under three hours. Your muscles don’t need it mid-session the way they do post-session. If you’re doing full-day OCR camp formats or extended adventure racing prep that extends beyond three hours, adding 10 to 15 grams of protein per hour helps slow muscle protein breakdown during prolonged effort. Practical options: protein-added sports drinks, real food carries (rice cakes with nut butter, jerky), or combination gels that include a small protein component.
Sodium often gets overlooked in the training context because athletes associate it with race-day cramping prevention. But extended OCR training sessions — especially those involving water obstacles, repeated soaking, and significant sweating — produce substantial sodium losses. Replacing sodium during the session (not just afterward) supports fluid retention, maintains plasma volume, and keeps muscle function sharp in the later stages of a hard training block. A rough target for heavy sweaters: 500 to 700 milligrams of sodium per hour during high-sweat-rate sessions.
The Skeptic’s Corner
Some coaches and athletes push back on the idea of intra-session fueling as a performance tool, arguing that training in a glycogen-depleted state builds fat-burning efficiency and metabolic resilience. There’s real science behind that position. Low-carb long sessions can improve fat oxidation capacity over time, and building the ability to push through mild glycogen depletion is genuinely useful for ultra-length events.
The honest answer is that both things are true, and periodization applies here too. Deliberate fasted or under-fueled training sessions have a place in a well-designed program. So do sessions where you nail your intra-session fueling and train the gut to process carbohydrates efficiently under physical stress. Gut training — systematically teaching your digestive system to absorb nutrition during hard exercise — is a performance variable in its own right. Athletes who have never practiced eating during hard effort will struggle to do it effectively on race day when it matters.
The goal isn’t to fuel every hard session maximally. It’s to know how to fuel well when the session demands it — and to have the gut tolerance and mechanical skill to execute it cleanly.
Practice the Mechanics, Not Just the Nutrition
This is the piece most athletes skip. The nutritional science is relatively simple. The operational execution — getting nutrition into your body efficiently during a hard OCR training session — requires practice.
Work out your carry system during training, not for the first time on race day. A lightweight race belt or soft flask holder that lets you access gels single-handed while moving is worth every dollar. Practice opening gel packaging with wet or chalked hands. Know which products you can open one-handed and which ones require a full stop. Time your feedings to lower-intensity movement phases — use the jog between obstacle circuits, not the middle of a carry simulation, to take in calories.
If you train with a group, establish a feed window in your session structure the same way you’d plan obstacle rotations. Not because it’s precious — but because athletes who make a deliberate habit of consistent intra-session nutrition develop better gut tolerance, more stable energy across long sessions, and the mechanical fluency to fuel efficiently when they actually need it at a long race.
The Bottom Line
Intra-session nutrition for long OCR training days is one of the most consistently underworked areas in amateur OCR athlete preparation. The variables are real: effort spikes that outpace steady-state fueling rules, wet and filthy hands that make access difficult, and hunger signals that reliably lie to you during high-intensity work. Build a system for it — when you feed, what you carry, how you access it — and practice that system in training. Your race-day fueling will improve as a side effect, but the more immediate payoff is finishing hard training sessions with more left in the tank than you’ve had before.
Find the Gear
The right carry system makes intra-session fueling actually executable — shop these categories to find what works for your setup.
- OCR Race Belts & Nutrition Carry Systems
- Endurance Energy Gels
- Electrolyte Chews & Sodium Tablets
- Sports Nutrition Chews for Training
- Soft Flasks & Running Vest Pockets
Wall & Wire is an independent OCR media outlet. We may earn affiliate commissions from purchases made through the links in this article, but our recommendations are based on what actually performs on OCR courses.
This article was researched with the help of AI tools and reviewed and edited by Hilton Campbell. Original reporting and quotes are our own.