OSJ KOUMI100 takes place on Sun, Oct 11, 2026 in Koumi, Japan. The main route is 165 km.
- Date
- Sun, Oct 11, 2026
- Start
- Koumi 🇯🇵
- Distance
- 165 km
- Level
- Open to all
OSJ KOUMI100 is a grueling 100-mile trail race held in Koumi, Nagano Prefecture, consisting of five 33km loops around Matsubarako Lake and Inago-yu.
Official event pageWhat this race demands
OSJ KOUMI100 demands absolute metabolic resilience and immense structural durability to complete five grueling 33km trail loops totaling 100 miles.
Ultra-Distance Endurance
Covering a 100-mile distance requires sustained cardiovascular output and extreme muscular endurance over many hours of continuous movement.
Loop-Based Pacing
The five 33km loop structure around Matsubarako Lake and Inago-yu demands strict pacing discipline to prevent early fatigue on repetitive terrain.
Structural Durability
Sustaining locomotion across multiple trail loops tests joint and connective tissue resilience against repetitive impact.
To sustain energy across a 100-mile trail race lasting well beyond standard endurance limits, athletes should target 60 to 90 grams of carbohydrates per hour.
Your road to race day
Race day at OSJ KOUMI100 is 7 weeks away. This is how a coach divides that time. The first phase starts now.
01Build1 week · Aug 24, 2026 – Aug 30, 2026
Progressive overload: training load climbs in waves, with harder weeks stacked on the base and planned recovery weeks that let the gains land.
02Peak3 weeks · Aug 31, 2026 – Sep 20, 2026
The hardest weeks of the plan: race-specific intensity at nearly full training load, sharpening exactly what this race asks for.
03Taper2 weeks · Sep 21, 2026 – Oct 4, 2026
Volume drops while intensity stays: short, sharp efforts keep the legs awake as fatigue drains away.
04Race week1 week · Oct 5, 2026 – Oct 11, 2026
Openers, rest and logistics. The work is done; the job now is arriving fresh.
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