Races
Sean O'Brien
Malibu. Sean O'Brien hundred k. Backbone Trail. Twelve thousand feet above the Pacific.
62 mi+415 ft-418 ft17 hours810 ft to 864 fttech 5/10Checkpoints per race bookBackbone TrailMalibuWSER qualifierFebruary
Distance62 mi
Gain+415 ft
Loss-418 ft
Altitude810 ft to 864 ft
Technicality5/10
Air45°F to 85°F
- Start820 ft
- High864 ft
- Low810 ft
- Finish817 ft
Field, 2026 · 12-year samplescraped
Starters86
Finish rate98%
Median14:52
Sub-2484
Geometryderived
Steepest drop46 ft-0.4% over 2.2 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. +415 ft gain and -418 ft loss. Surfaces skew 90% trail / 10% fire road. Backbone Trail exposed ridges above Malibu. High point near 864 ft. Low near 810 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 415 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