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Grindstone Trail Running Festival by UTMB
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Grindstone 21K

UTMB World Series
21.0km·500m+
September 25, 08:00 AM
Natural Chimneys Park,
United States
utmb·source

Race Pace Calculator · GPX Analyzer · Trail Finder

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Full calendar: United States

Grindstone 21K · Race profile

Distance
21.0km
Gain
500m+
Max
738m
Min
409m

About Grindstone 21K

Grindstone 21K is the 21.0km trail race at Grindstone Trail Running Festival by UTMB 2027 (Natural Chimneys Park, United States). The race starts on September 25, 2027 at 08:00 AM. It starts in Natural Chimneys Park. The time limit is 6 h.

Race strategy

Run the climb at race pace, build your speed on the downhill, and go all out at the finish.

  • Start easy and control your HR up to 9.8km.
  • Hold your race pace up to 12.3km, but stay in control.
  • The finish is runnable. Save your legs to run it all the way.
  • Ease into the early runnable section, then run your race pace.
  • Start · 0.0km–2.7km · Race-day nerves push your heart rate up: don't follow the crowd, find your own rhythm.
  • Settle in · 2.7km–9.8km · 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 · 9.8km–12.3km · Descent of 227m averaging 9%, high point 738m. This is where the race is built: steady, solid effort.
  • Home · 12.3km–21.7km · 9.4km of runnable trail. Build to the finish: leave whatever you have left out on the course. Running pays off here: run wherever you can.

Course

The course climbs 500m+. With 24m/km of climbing, the course is predominantly runnable. By gradient, 20% of the distance is uphill, 19% downhill and 61% flat. The longest climb runs 4.6km at an average 7.0% grade (321m of vertical). The longest descent runs 2.5km at an average 9.2% grade (227m of vertical). The steepest climb averages 28.7% over 0.4km. The steepest descent drops at 21.6% over 0.4km. Surface: 35% trail, 31% road, and 22% smooth.

Poles

The course is runnable enough that trekking poles are not needed.

Quad damage

There is too little runnable descent to damage the quads: plan the race around climbing and fuelling.

This page has a pacing and nutrition planner, a gradient matrix, an interactive elevation profile and historical weather for Grindstone 21K.

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

Other editions of Grindstone 21K2025

Official websitegrindstone.utmb.world