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Grindstone Trail Running Festival by UTMB
167.4km167.4100km10050km5021km21

Grindstone 100K

UTMB World Series
100.0km·3350m+
September 25, 06:00 AM
Natural Chimneys Park,
United States
utmb·source

Race Pace Calculator · GPX Analyzer · Trail Finder

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Read

  • How to Taper for a Marathon, Half Marathon or Ultra
  • Types of Runs and What Each Workout Actually Trains
  • Hill Training for Trail Runners: Train the Descents

Full calendar: United States100K trail race calendar

Grindstone 100K · Race profile

Distance
100km
Gain
3350m+
Max
1313m
Min
408m

About Grindstone 100K

Grindstone 100K is the 100km ultra trail at Grindstone Trail Running Festival by UTMB 2027 (Natural Chimneys Park, United States). The race starts on September 25, 2027 at 06:00 AM. It starts in Natural Chimneys Park. The time limit is 18 h.

Race strategy

Hold a steady pace and save energy for every section.

  • 634m descent. Go easy, save your quads.
  • The finish is runnable. Save your legs to run it all the way.
  • Long race. Control your HR and effort. Early mistakes cost the most.
  • Ease into the early runnable section, save your quads on the descents until 85.4km, then run your race pace.
  • Start · 0.0km–2.0km · Race-day nerves push your heart rate up: don't follow the crowd, find your own rhythm.
  • Settle in · 2.0km–18.4km · Plus 1 more climb. Ease in: hold back more than feels necessary. The race is still ahead. Climb by heart rate or breathing, not pace. Running pays off here: run wherever you can.
  • Work · 18.4km–54.5km · Climb of 672m, descent of 634m averaging 8%, climb of 750m. This is where the race is built: steady, solid effort. Climb by heart rate or breathing, not pace. This descent is hard on the legs: short steps, stay in control, poles if you have them.
  • Fade · 54.5km–85.4km · Descent of 425m averaging 6%, climb of 631m, high point 1325m, descent of 1025m averaging 9%. Your energy fades, and that's normal: hold a steady effort and stop counting the miles. Climb by heart rate or breathing, not pace. This descent is hard on the legs: short steps, stay in control, poles if you have them. Running pays off here: run wherever you can. Your heart rate drifts down on its own: don't chase your early-race numbers, go by feel.
  • Home · 85.4km–105km · 19.3km of runnable trail. No heroics: settle back into your own effort and hold it to the line. Running pays off here: run wherever you can.

Course

The course climbs 3350m+. With 34m/km of climbing, this is a rolling, mostly runnable course. By gradient, 33% of the distance is uphill, 31% downhill and 37% flat. The longest climb runs 17.4km at an average 4.3% grade (750m of vertical). The longest descent runs 11.0km at an average 9.3% grade (1025m of vertical). The steepest climb averages 28.7% over 0.4km. The steepest descent drops at 21.4% over 0.5km. Surface: 55% trail, 30% smooth, 11% road, and 5% extreme.

Summits

The highest summit on the course is Little Bald Knob (1320m), 74.4km from the start. Other named summits along the route: Hankey Mountain (1051m). The course also passes close to Sand Spring Mountain (1137m).

Poles

Poles bring little benefit here: only about 9.2km of pole-friendly terrain.

Quad damage

Quad damage risk is moderate (index 35 of 100), with 29% of the load in the first half: 3 descents deserve a plan and a couple of downhill sessions before race day.

  • Ease into the early runnable section, save your quads on the descents until 85.4km, then run your race pace.
  • #1 · 28.7–37.1 km · 634 m D−, -7.6% · 67.6 km ahead → control
  • #3 · 54.5–61.7 km · 425 m D−, -5.9% · 42.9 km ahead → control
  • #2 · 74.4–85.4 km · 1025 m D−, -9.3% · 19.3 km ahead → control

This page has a pacing and nutrition planner, a gradient matrix, an interactive elevation profile and historical weather for Grindstone 100K.

Other distances of Grindstone Trail Running Festival by UTMB 2027Grindstone 100M (167km)·Grindstone 50K (50.0km)·Grindstone 21K (21.0km)

Other editions of Grindstone 100K2026·2025

Official websitegrindstone.utmb.world