An Eryri training plan (formerly Ultra-Trail Snowdonia) has to get you ready for Welsh mountains at their roughest: exposed ridges, scree, boulders, boggy moorland and the climb to Yr Wyddfa (Snowdon), the highest peak in Wales. Altitudes are modest, but the 100M packs as much climbing as the big Alpine ultras. Here is how to train for each of the five races.
The short answer
- Allow 12 to 16 weeks of specific training for the 25K and 50K, 5 to 6 months for the 80K and 100K, and 6 to 12 months for the 100M.
- Indicative peak load: 40 to 60 km and 1500 to 2500 m of climbing per week for the shorter races, 60 to 90 km and 3000 to 4500 m for the ultras, depending on your level.
- Key sessions: long climbs with power hiking, rocky descents, long technical mountain runs, back-to-back weekends.
- Number one challenge: very technical terrain and a very high climbing ratio, especially on the 100M and the 50K.
Contents
Eryri by UTMB distances and elevation
Renamed Eryri by UTMB, the event takes place in May in Eryri (Snowdonia) National Park. Figures come from the official Eryri by UTMB website; check them before race day.
| Race | Distance | Elevation gain | Profile/notes |
|---|---|---|---|
| Eryri 100M (100M category) | 163 km | 9200 m | Start and finish in Llanberis; 48-hour time limit; 4 Running Stones |
| Eryri 100K (100K category) | 108 km | 5800 m | Highly technical mountain ultra |
| Eryri 80K (100K category per the site) | 78 km | 2500 m | The most runnable of the ultras |
| Eryri 50K (50K category) | 56 km | 3400 m | Short but steep: over 60 m of climbing per km |
| Eryri 25K (20K category) | 25 km | 1300 m | Entry-level format, already proper mountain running |
The official site describes technical trails and exposed ridges, scree fields, boulder-strewn paths and boggy moorland. The 100M climbs Yr Wyddfa and passes Llyn Gwynant and Llyn Idwal, as well as relics of the slate industry. Welsh weather in May can still bring rain, wind and hill fog.
What makes Eryri by UTMB so demanding
Look at the climbing ratio first. 9200 m over 163 km means two days of steep ups and downs. The 50K is a trap if you compare it with a standard 50 km race: 3400 m of climbing makes it a long, muscular effort. Then there is the ground itself. Scree and boulders slow you down even on descents, and wet moorland tires your ankles. On the 100M, a night on exposed ridges calls for clear thinking, a reliable headtorch and proper kit; the mandatory kit list is on the official website.
How long do you need to prepare?
The 25K takes 10 to 12 weeks if you already run regularly in the hills. The 50K needs 14 to 16 weeks and a previous mountain race of 30 to 40 km with at least 2000 m of climbing. The 80K and 100K call for 5 to 6 months and one or two finished ultras over 50 km. The 100M needs 6 to 12 months and experience of at least one mountain 100 km or an effort lasting over 20 hours. Our guide to increasing distance in trail running explains how to build up safely.
The phases of your training plan
Base phase. Lots of easy running, one quality session a week and two strength sessions (squats, lunges, box step-ups, core, ankle stability). Start accumulating some regular climbing, even if modest.
Specific phase. The heart of your preparation: long climbs, technical descents and long mountain days. Increase climbing gradually, with a lighter week every three or four weeks. For the ultras, add back-to-back weekends and night runs.
Taper. Two to three weeks out (one to two for the 25K), cut volume by 30 to 50% while keeping a few short efforts.
Key sessions for Eryri by UTMB
Long climbs with power hiking: for example 3 to 5 x 10 to 15 minutes of steep climbing at a sustained effort, mixing running and fast hiking.
Rocky descents: repeated descents on stony trails, staying relaxed and looking two or three steps ahead. This is what makes the difference on scree.
Long technical runs: 4 to 7 hours in the mountains for the ultras, testing fuelling and kit. Time on feet matters more than distance.
Back-to-back weekends: two long runs on consecutive days for the 100K and 100M, to learn to run on tired legs.
The RunMotion Coach app builds a personalised, adaptive plan that adjusts every week to the sessions you complete and your availability, with elevation, strength and recovery built in. RunMotion Coach is the official online coach of the UTMB World Series, and its founders, twins Guillaume and Romain Adam, come from the Alps, so mountains and big climbs are their home ground. Try it free for 7 days.
Plan your race strategy with Race Strategy
On such varied ground, your pace can halve between a path and a boulder field. Race Strategy by RunMotion calculates your strategy kilometre by kilometre, with pace adjusted for elevation, altitude and terrain technicality, estimated split times at key points, a nutrition and hydration plan for each section (carbs, water, sodium) and a race-day weather adjustment. Just import the official GPX of your race.
Running Stones and the UTMB World Series
Eryri by UTMB is part of the UTMB World Series. The official site lists 4 Running Stones for the 100M; the other races earn Running Stones according to their category. To plan your season, read our UTMB World Series training plan guide and our article on planning your trail running season.
FAQ
Do you need poles for Eryri by UTMB?
Check the official race rules for poles. They can help on long steep climbs but get in the way on boulder sections. If you use them, train with them.
Is Ultra-Trail Snowdonia the same race as Eryri by UTMB?
Yes. The official site presents Eryri by UTMB as the new name of Ultra-Trail Snowdonia by UTMB, in the same national park.
How much climbing per week for the 100M?
At peak, many runners sit between 3000 and 4500 m of climbing per week, but it depends on your history and access to hills. Progression and recovery matter most.
Conclusion
Eryri by UTMB demands strong legs uphill and downhill, reliable ankles and experience on technical ground. Build your preparation progressively and target the right sessions. For a plan that adapts to you, start your 7-day free trial of RunMotion Coach.
Article updated by the RunMotion Coach team.
Sources: eryri.utmb.world, Eryri 100M race page.
