Cornwall · January · UTMB World Series

Arc of Attrition by UTMB

The UK's toughest winter coastal ultra. 100 miles along Cornwall's South West Coast Path in January — with a 50% drop-out rate and brutal winter conditions.

4 Distances

12km–161km

January

Race Date

~50%

DNF Rate

UTMB Series

Running Stones

The Distances

Arc 100

161km · 4,010m+ · Coverack to Porthtowan. 36-hour cut-off. The UK's hardest winter 100-mile ultra.

4 Running Stones

Arc 50

80km · 2,500m+ · Minack Theatre to Porthtowan. 15.5-hour cut-off. Past Land's End along the dramatic southern tip.

3 Running Stones

Arc 25

40km · 1,000m+ · Near St Ives to Porthtowan. 8-hour cut-off. Dramatic terrain, dunes and cliffs.

2 Running Stones

Arc 12

24km · 500m+ · Godrevy to Porthtowan. Perfect introduction to coastal ultra running.

1 Running Stone

What Makes the Arc 100 Special

The Arc 100 starts at midday on a Friday in late January and runs through the night — which for most runners means two nights of darkness. The South West Coast Path from Coverack to Porthtowan is relentlessly undulating, with no flat sections. The winter weather can be brutal — storms, high winds, driving rain and cold temperatures are all common.

The course carries approximately 4,500m of elevation despite being a coastal race — the constant cliff path climbing and descending adds up fast. The section after mile 40 around Porthcurno and Land's End is where the race character changes dramatically — granite bouldering, big cove climbs and serious technical running.

Key Facts

Arc 100 recommended UTMB Index: minimum 380
The Arc 100 has a ~50% finish rate in a typical year — higher in bad weather
Support crew are allowed at designated points on the Arc 100
No personal assistance on the Arc 50
Sub-24 hour Arc 100 finishers receive a Black Buckle
Both arc events are part of the UTMB World Series
First held in 2015 — now one of the UK's largest trail events

Preparation Tips

Night Running

The Arc 100 involves at least one full night of running, often two. Include structured night running sessions in your build-up. Practice your lighting setup and navigation in the dark.

Coastal & Winter Training

Train in wind and rain — don't wait for good weather. The coast path conditions are brutal in January. Your body needs to be conditioned for wet, cold running over many hours.

Don't Rush the First Half

Every finisher starts slower than training pace for the first 20-25 miles. The back half is where the race is won or lost — the technical sections after mile 40 slow everyone down significantly.

Kit & Self-Sufficiency

Long gaps between aid stations on the Arc 100 mean extended self-sufficiency. Know your mandatory kit inside out, and carry enough food and water for the remote sections.

Training for Arc of Attrition?

We build bespoke training plans and coaching packages for this race. Get in touch to discuss your preparation.

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