Races
Sean O'Brien
Malibu. Sean O'Brien hundred k. Backbone Trail. Twelve thousand feet above the Pacific.
62 mi+21,552 ft-21,552 ft17 hours72 ft to 2,408 fttech 5/106 stationsBackbone TrailMalibuWSER qualifierFebruary
Distance62 mi
Gain+21,552 ft
Loss-21,552 ft
Altitude72 ft to 2,408 ft
Technicality5/10
Air45°F to 85°F
- Start535 ft
- High2,402 ft
- Low75 ft
- Finish535 ft
- California at mile 0.0
- Sean O'Brien mile 12 at mile 12, cutoff 3.4000000000000004 hours
- Sean O'Brien mile 25 at mile 25, cutoff 6.800000000000001 hours
- Sean O'Brien mile 37 at mile 37, cutoff 10.2 hours
- Sean O'Brien mile 50 at mile 50, cutoff 13.600000000000001 hours
- Finish California at mile 62, cutoff 17 hours
Field, 2026 · 12-year sampleresults
Starters86
Finish rate98%
Median14:52
Sub-2484
Geometrycourse math
Steepest drop1,191 ft-12.1% over 1.9 mi
Night miles23 misunset near 18:00 local
Course records
Men8:24:35Christopher Wehan
Women9:38:17Courtney Dauwalter
The cruxBackbone Trail exposed ridges above Malibu (near mile 40)
Course DNA
The Course
Sean O'Brien runs 100 km through California. +21,552 ft gain and -21,552 ft loss. Surfaces skew 90% trail / 10% fire road. Backbone Trail exposed ridges above Malibu. High point near 2,408 ft. Low near 72 ft. February temps run 45°F to 85°F. The course rewards patience early and punishes rushed descents after mile 31.
The Work
Train for 21,552 feet of climbing across 100 km. Back-to-back long runs on trail. Practice power-hiking grades above 15 percent. 17 hours total means limited margin: rehearse fueling every 45 to 60 minutes and downhill eccentric work weekly. Technicality 5/10. Build a block that simulates the crux near mile 40.
Kit
February in California: plan for 45°F to 85°F. Mandatory shell if rain is in forecast. Headlamp with spare batteries if 17 hours pushes past dark. Poles help on sustained climbs above mile 16. Vest capacity for 2 liters minimum. Shoes matched to 90% trail: lugs for mud, rock plate if the course turns technical after mile 31.
Race Day
Hold effort through mile 16. The field often splits on the first big climb after mile 31. Backbone Trail exposed ridges above Malibu near mile 40 is where time is won or lost. Walk the steep pinches. Run the flats and gentle downhills. Crew at major aids: socks, calories, ice if hot. Transitions under 5 minutes when possible. Final third is 21 miles of fatigue management. Finish with reserve for the last descent.
Results
Sean O'Brien finish lines.
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Sources (3)
- Field stats (2026): https://ultrasignup.com/results_event.aspx?did=125436
- Course record (M): https://ultrasignup.com/results_event.aspx?did=38282
- Course record (F): https://ultrasignup.com/results_event.aspx?did=46885