Ushuaia by UTMB
Ushuaia by UTMB – CHALLENGE 50K
Ushuaia
Race guide
Updated 18 July 2026
The CHALLENGE 50K is the 50 km option at Ushuaia by UTMB, run in Tierra del Fuego at the southern tip of Argentina. It is a loop that starts and finishes in Ushuaia at sea level, and despite its shorter distance it is a serious mountain outing, cramming 2,506 m of vertical gain into just 50 km and reaching a high point of 912 m. That climb-to-distance ratio makes the CHALLENGE 50K a steeper, more concentrated test than the numbers first suggest. Where the longer Ushuaia races spread their climbing out, this course goes up hard and early and keeps the pressure on. Add the sub-Antarctic setting and its notoriously fickle weather, and you have a compact but demanding race at the end of the world.
The Course: Short but Steep
The CHALLENGE 50K starts and finishes in Ushuaia at 0 m, making the full 2,506 m of climb a genuine out-and-back from sea level. The defining feature comes early: the climb to Glaciar Martial at 12.1 km, which reaches 329 m at the checkpoint but takes you up toward the course's 912 m high point on the glacier's flanks above the city. This is a big, front-loaded ascent that sets the tone for the whole day. From the high ground the route works its way to Arakur (28.5 km, 248 m), then descends to Olivia River 1 (37.5 km, 175 m) before the final checkpoint at Alarken (45.2 km, 249 m) and the closing drop back into Ushuaia at 50 km. With only four intermediate checkpoints across 50 km, the legs between aid are long and the terrain in between is steep, so the profile feels far bigger than a standard 50 km race.
Where the Race Is Decided
The Glaciar Martial climb inside the first 12 km is the crux of the CHALLENGE 50K. It is the steepest sustained effort on the course and it takes you to the highest ground of the day at around 912 m, so how you manage that ascent shapes everything after it. Push too hard to the top and you will pay across the long middle section; hold back too much and you risk the later cut-offs. Reaching Glaciar Martial (12.1 km, 329 m) controlled and fuelled is the single most important decision of your race. The second half, from Arakur (28.5 km, 248 m) through Olivia River 1 (37.5 km) to the late climb up to Alarken (45.2 km, 249 m), is where the early effort is repaid or regretted. That final rise to Alarken before the descent to the finish comes on tired legs and is where runners who over-invested on the glacier climb tend to fade.
Pacing and Fuelling to the Cut-Offs
The cut-offs are set on the same race day: Arakur closes Saturday at 12:40, Olivia River 1 at 16:30, Alarken at 18:30 and the finish at 19:00. The long gap between the start and the Arakur cut-off covers the big Glaciar Martial climb, so use that section to build a buffer while you are fresh, then protect it through the second half where the closing checkpoints come in quicker succession. With just four intermediate stops, you need to carry enough food and fluid to cover the long, steep legs, particularly the opening climb to Glaciar Martial and the stretch through to Arakur. The finish at Ushuaia is the sole crew point on the loop, so this is largely a self-sufficient day out; pack your nutrition and layers accordingly and do not count on frequent resupply. Aim to reach Arakur comfortably ahead of its 12:40 cut-off to give yourself room on the back half.
Conditions to Expect
Ushuaia's location in sub-Antarctic Tierra del Fuego means the CHALLENGE 50K can throw genuine mountain weather at you despite its modest 912 m high point. The exposed ground around Glaciar Martial catches wind, cold and rain rolling off the peaks, and conditions can shift fast between the sheltered valleys and the open high sections. The sea-level start in town is no guide to what you will meet up on the glacier's flanks. The terrain is steep and rugged, with rocky mountain trail higher up and softer, wetter ground in the valleys that can slow your pace after rain. Carry windproof and warm layers even for this shorter race, dress for the summit rather than the start line, and keep your effort honest on the big early climb. The elevation numbers understate the difficulty here, so set conservative time goals and give the weather the respect the end of the world demands.
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Checkpoints & cut-offs
✓ Course data verified against the official source (2026-07-17) · official source
0 km · 0 m · —
12.1 km · 329 m · —
28.5 km · 248 m · Sat 12:40
37.5 km · 175 m · Sat 16:30
45.2 km · 249 m · Sat 18:30
50 km · 0 m · Sat 19:00
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