What Is the OCC?
OCC stands for Orsières–Champex–Chamonix — the route of the race. It starts in Orsières in Switzerland, climbs through the Val d'Entremont and over the Col de Balme, crosses the Franco-Swiss border several times, and finishes in the centre of Chamonix during UTMB week each late August.
It is one of the three Finals races of the UTMB World Series — the annual 50K-category final, sitting alongside the CCC (the 100K final) and UTMB itself (the 100M final). For the 2026 edition the course was redesigned in its upper section, and now runs 60km with around 3,500m of climbing, with a new high point at 2,321m and a maximum allowed time of 14 hours 30 minutes.
That distance-and-climb combination puts the OCC in an interesting physiological sweet spot: the classic engine measures — VO₂max, lactate threshold, running economy — still correlate strongly with your result, yet the demands of mountain terrain mean strength, descending skill and fatigue resistance increasingly decide who runs well in the final third.
Because the OCC is a Final, you can't simply enter it. Your place has to be earned through the UTMB World Series system — so this guide covers qualification first, then training.
How to Qualify for the OCC
To enter the OCC lottery you need two things: at least one Running Stone earned in the past 24 months, and a valid UTMB Index in the 20K, 50K, 100K or 100M category. Pre-registration opens in December, and the lottery is drawn in January.
What Is a Running Stone?
A Running Stone is a ticket into the Finals lottery. You earn stones by finishing UTMB World Series races in the 20K, 50K, 100K or 100M categories — at the Majors (one per continent) you earn double. Finishing the Finals races themselves does not award stones.
- Your number of stones equals your number of chances in the draw — six stones means six entries.
- If you're drawn, your stones are spent and reset to zero.
- If you're not drawn, you keep your stones and they roll forward to future years.
- At least one of your stones must have been earned in the past 24 months.
What Is the UTMB Index?
The UTMB Index is a performance score calculated from your results in UTMB Index-certified races over roughly the past two to three years, held per category (20K, 50K, 100K, 100M). For the OCC, a valid index in any of the four categories is accepted, and it only needs to be valid at the time of pre-registration — not on race day.
Direct Qualification
Beyond the lottery, top finishers earn automatic places: category winners and podiums at Majors and World Series events can qualify directly, and UTMB operates elite qualification windows for the sharp end of the field. For most runners, though, the path is stones plus lottery.
Your Path, Step by Step
- Finish one or more UTMB World Series races in the 20K–100M categories to earn Running Stones.
- Make sure at least one result gives you a valid UTMB Index (any category from 20K up works for the OCC).
- Pre-register for the OCC in December and wager your stones.
- Drawn in January? You're in. Not drawn? Your stones roll forward for next year.
- Alternatively, chase a direct slot with a top finish at a Major or World Series event.
Plan qualifying races well ahead — travel, cost and entry windows all matter, and popular events sell out early.
Training Strategy for the OCC
A 60km race with 3,500m of climbing has to be trained for on four fronts at once: the aerobic engine, strength and durability, technical terrain skill, and fuelling. Neglect any one and the course finds it.
What the Evidence Says to Emphasise
- VO₂max builds your ceiling — in races of this length it still correlates strongly with performance.
- Lactate threshold decides what fraction of that ceiling you can actually sustain — for most runners this deserves the greater emphasis.
- Running economy is free speed, on climbs as much as flats — and research on graded running suggests uphill-specific economy is its own quality that needs its own training.
- Strength — especially quads, glutes, calves and core — is what survives 2,000m of descending.
- Fatigue resistance, gut tolerance and recovery quietly decide the final two hours.
Periodisation
Base (3–4 months): volume and easy aerobic hours, hills and trails, light strength work, and early technical skill practice — especially descending confidence.
Build (2–3 months): hold the volume, add threshold and long hill intervals, introduce VO₂max work without overdoing it, add eccentric-focused strength and plyometrics for downhill loading, and start race-simulation days on OCC-like terrain, including back-to-back days.
Peak (3–4 weeks): taper the volume but keep touches of intensity, rehearse race pace on terrain, and finalise fuelling and kit — nothing new after this point.
Race and recovery: execute the plan, then recover properly and review what you learned.
Key Sessions
- VO₂max: the classic 4 × 4 minutes at 90–95% effort with 3-minute jog recoveries is effective and manageable. Keep high-intensity work to roughly a fifth of weekly load or less.
- Threshold: 20–30 minutes continuous at “comfortably hard” — the pace where speech drops to a word or two — or intervals like 3 × 10 minutes. Extend as fitness builds, ideally on rolling ground.
- Long runs: on terrain that resembles the OCC — sustained climbs, technical descents, uneven surfaces. Every few weeks make it a genuinely long mountain day (4–6 hours), and use occasional back-to-back days to train running on tired legs.
- Strength: two sessions a week, 8–12 rep range, with deliberate eccentric work — controlled downhill repeats and eccentric calf lowering — plus bounding and hops for economy.
- Technique: practise foot placement, rock-hopping and descending lines on real technical ground, and learn to climb efficiently: shorter strides, strong posture, and power-hiking when it's faster than running.
Fuelling and Gut Training
Practise your race fuelling on every long run — the gut adapts to absorbing carbohydrate under stress, but only if you train it. Recent research supports very high intakes (towards 120g of carbs per hour) reducing muscle fatigue in mountain ultras if tolerated, which is precisely why it has to be rehearsed. Our full guide on how to fuel an ultra covers targets and an hour-by-hour approach, and do ultra runners really need gels? weighs gels against real food.
An Example Build-Phase Week
- Monday: recovery run + light strength and core.
- Tuesday: threshold — 3 × 12 minutes comfortably hard, 3-minute jog recoveries.
- Wednesday: medium trail run with hills, steady aerobic, plus drills.
- Thursday: VO₂max — 5 × 4 minutes at 90–95% with full warm-up and cool-down.
- Friday: easy run + lower-limb strength and mobility.
- Saturday: long mountain run (3–4 hours) over mixed terrain, final hour progressive.
- Sunday: easy active recovery or rest.
Adjust around fatigue, terrain access and life — the plan serves you, not the other way round.
Race Strategy & Tactics
- Pacing: stay below threshold through the early sections — the race is decided after Col de Balme, not before it.
- Fuelling: start early and stay consistent; never let yourself run empty before reacting.
- Descents: avoid over-braking — it shreds the quads. Pick lines early and let the gradient work for you.
- Conditions: alpine weather and altitude change quickly; have contingency pacing in mind.
- Mental structure: break the course into checkpoint-to-checkpoint segments with micro-goals.
- Cut-offs: know them cold — staying ahead of them is as much a part of the race as speed.
Common Pitfalls
- Chasing VO₂max, neglecting threshold and volume — the most common imbalance, and it backfires in the final third.
- Under-training strength — you pay for it on the descents into Chamonix.
- Training on roads, racing on mountains — terrain specificity is not optional here.
- Ignoring recovery — accumulated fatigue derails more OCC builds than missed sessions do.
- Race-day experiments — every fuelling and kit choice must be validated in training first.
- Leaving qualification late — stones races sell out, and the December window comes around fast.
Frequently Asked Questions
What does OCC stand for?
Orsières–Champex–Chamonix — the route of the race, from Orsières in Switzerland to the finish in Chamonix, France. It's the 50K-category final of the UTMB World Series.
How long is the OCC?
The 2026 edition is 60km with around 3,500m of climbing, and a maximum allowed time of 14 hours 30 minutes.
How do I qualify for the OCC?
At least one Running Stone earned in the past 24 months, plus a valid UTMB Index in the 20K, 50K, 100K or 100M category. Pre-register in December; the lottery is drawn in January. Top finishers at Majors and World Series events can qualify directly.
Do I lose my Running Stones if I am not drawn?
No — undrawn stones roll forward to future years. If you are drawn, your stones are spent.
Which UTMB Index do I need for the OCC?
A valid index in any of the 20K, 50K, 100K or 100M categories, valid at the time of pre-registration.