How to Train for the OCC: A Coach's 16-Week Framework

The OCC is the race in UTMB week that road runners and shorter-distance trail runners look at and think "I could do that". Often they can, and it is a fantastic first big-mountain race. What catches people is the ratio: 3,500 m of climbing in 60 km is almost exactly the CCC's steepness with less than half the distance to absorb it. This is the framework I use to prepare a runner for it, aimed at a finish between 8 and 13 hours.

The course is adjusted from year to year. The figures here are the official 2026 edition; check the official OCC page for the current profile and cutoffs before planning around them.

What the OCC actually demands

• Distance and climb. 60 km and 3,500 m of gain in 2026, about 58 m of climbing per kilometre. Orsières sits at around 900 m, Chamonix at about 1,035 m, so the descent total is close to the climb total.
• The start. Thursday at 08:15, in a large field. The early climbs out of the Swiss valley toward Champex-Lac are done in traffic, and the temptation to push around people costs more than it gains.
• The high point. Tête de Balme, at 2,321 m, is the top of the course in the 2026 edition, with the border crossing at Col de Balme and the Col des Posettes on the way down toward Le Tour. It is high enough to be cold and exposed if the weather turns, and low enough that altitude itself is not a performance factor for most people.
• The end. Vallorcine, then the final climb out of the valley floor before the long descent to Chamonix. This is the classic UTMB-week finish: the last ascent arrives on legs that have already done 3,000 m, and the descent into town is steep, technical in places, and full of people who started too fast.
• The clock. 14 hours 30 minutes. Winners are around 5 hours; a competitive age-grouper is 6-8; most of the field is 8-13. Almost everyone finishes in daylight, which changes the training: no night sessions required, and more intensity permitted.
• Heat. Late August in the Chamonix valley is regularly hot in the afternoon. The final descent is the warmest part of the day for a mid-pack runner.

Who this framework is for

The OCC is a good target if you have finished at least a trail marathon or a hilly 50K and can currently run 40-50 km a week with some climbing in it. It is also a sensible stepping stone toward the CCC or the UTMB, and a much better first race in the mountains than the CCC is, because it ends before the night and before the gut usually fails. If you are deciding between them, the first ultra distance guide is written for that decision.

Entry needs at least one Running Stone from a UTMB World Series race. Pick that qualifier deliberately: a 30-50 km race with 1,500-2,500 m of gain, 8-16 weeks before the OCC, doubles as your rehearsal.

The 16-week structure

Each block runs in four-week cycles of three loading weeks and one recovery week. For a sub-8-hour target, add 15-20% to the vert and hold the km; for a finish-inside-the-cutoff target, hold the durations and reduce everything else by 15%.

Base: weeks 1-4

Four to five runs a week, mostly easy. Two things start now and never stop: a weekly strength session built around single-leg work and eccentric loading, and a weekly steep hike of 45-75 minutes with poles. The OCC is short enough that people skip the hiking work and pay for it on Tête de Balme.

Build: weeks 5-10

This is where the OCC plan diverges from a CCC or UTMB plan. Because the race is run at a genuinely hard effort for most of the field, the build keeps two quality sessions a week rather than one:

1. Climbing intervals. 5-8 repeats of 3-5 minutes uphill at an effort you could hold for about an hour, jog or hike down. This is the single best predictor of an OCC finish time I know of: sustainable climbing power.
2. A rolling tempo. 30-50 minutes at a firm effort on undulating trail, which teaches the transition from climb to run to descent that the OCC asks for repeatedly.

Long runs build from three to four hours with 1,200-1,800 m of gain, on the steepest terrain you have access to. If that terrain is flat, the vertical gain training guide covers how to manufacture it. From week 7, finish every second long run with a hard 20-30 minute descent, and add a dedicated downhill session of 4-6 fast repeats on a 150-250 m drop in the other weeks. The OCC's descents are runnable, which means people run them, which means the quads get shredded by kilometre 45 unless they were trained for it.

Peak: weeks 11-13

The rehearsal race goes in week 11 or 12. Run it at OCC effort, with OCC kit, poles, and fueling, and treat the result as data. The biggest training weeks sit here: 60-75 km, 2,000-3,000 m, and one long run of 4-5 hours.

If your race is likely to be hot, this is also when heat acclimation goes in: 10-14 days of deliberate heat exposure ending a few days before the race, which buys real minutes on that final descent.

Taper: weeks 14-16

A taper of three weeks is slightly long for a 60 km race; two and a half is usually right. Volume drops by about a third, then two-thirds, while one short quality session stays each week until five days out. The last long run of 2-2.5 hours goes in week 14.

Fueling a 10-hour effort

Aim for 60-90 g of carbohydrate per hour from the first hour. At OCC intensity the gut is under more strain than in a 24-hour race, so the training runs from week 5 onward should practise eating at race effort, not just at long-run effort. Hydration follows the heat: sodium and fluid needs on the afternoon descent are the ones to plan for, not the cool morning start.

Pacing a 14-hour-30 cutoff

The OCC rewards even effort more than most races because the climbs are steep enough to hike and the descents are runnable. Practical structure for a 10-hour plan:

• Orsières to Champex-Lac. Conversational on the climbs, in a queue if necessary. Anyone passing you here on a steep section is making a decision they will revisit later.
• The high section over Tête de Balme. Steady, hydrate, layer if it is cold at the top, and run the descent through Col des Posettes toward Le Tour with restraint: it is long, and the legs that arrive in Vallorcine are the ones you race the last climb on.
• Vallorcine to Chamonix. The last climb is a grind; hike it well with poles and eat before it, not on it. The final descent is where the race is won or lost for age-groupers, and it is won by the runner whose quads are still there.

The trail ultra pacing guide has the full effort-based method; the OCC-specific note is that a slightly negative split is achievable here in a way it rarely is at 100 km.

The mistakes I see most

• Treating it as a long run. The OCC is racing. Runners who only train easy volume arrive aerobically fit and unable to sustain the climbing effort the race asks for.
• Skipping the hike work because "I can run 50K". You will not run Tête de Balme. Nobody does.
• Under-training the descents. Same story as every mountain race, compressed into a day: the quads decide the last 15 km.
• Chasing a road-marathon-style taper. Two to two and a half weeks is enough. Three weeks of sharp reduction leaves people flat on the start line.
• Racing the first climb. The most expensive ten minutes of the day.

What a coach changes here

The OCC is the race where I most often see a fit runner under-perform their fitness: the intensity and the descending are specific skills, and a plan that treats it as a shorter CCC leaves them on the table. If you want this framework built around your calendar, your terrain, and the qualifying race you actually have entered, that is what coaching is for. If you are self-coaching, run the race readiness score six weeks out and be honest about the downhill dimension.