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Race guide · California, USA
How to train for the Sean O'Brien Trail Runs
A rugged Santa Monica Mountains classic: singletrack and fire road on the Backbone Trail, with a lot of climbing for the distance. Here's what to know and how to get ready.
Next race Sat Jan 30, 2027
| Distance | Climb | Start | |
|---|---|---|---|
| 100K | 61.7 mi | 13,179 ft | 5:30 AM |
| 50 Mile | 49 mi | 11,492 ft | 6:00 AM |
| 50K | 32.1 mi | 6,719 ft | 7:00 AM |
All distances start and finish at Malibu Creek State Park in Calabasas.
What makes it hard
Big climbing for the distance
The 100K climbs 13,179 ft, more than 200 ft for every mile, with just as much descent.
Train for it: Weekly hill repeats, power hiking on steep grades, and leg strength for the descents.
Singletrack and fire road
You switch between fast fire road and technical singletrack all day, which makes pacing tricky.
Train for it: Long runs that mix both, and practise running the runnable climbs.
A long day from the dark
The 100K starts at 5:30 AM, so the first hours are by headlamp, and most runners are out all day.
Train for it: Early-morning long runs with your headlamp, and fuel on a schedule.
How long to train
Plan on 20–24 weeks for the 100K, 18–22 for the 50-miler and 12–16 for the 50K if you're already running 4–5 days a week.
Get a plan built around race day
Set Sean O'Brien as your goal race and VertPro builds your training back from the start line, then adapts week to week. A Vert.run coach reviews your plan in the first 24 hours.
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How much climbing is the Sean O'Brien 100K?
13,179 ft over 61.7 miles. The 50-miler has 11,492 ft and the 50K 6,719 ft.
When is Sean O'Brien 2027?
Saturday, January 30, 2027, at Malibu Creek State Park, according to the organiser. Always confirm on the official race site.
Race facts checked October 2, 2026 against khraces.com. Confirm dates and rules with the organiser. Vert.run is not affiliated with the race.