OSJ大地沢50K 2026

The OSJ Daichizawa 50K is a small summer trail race held at Machida Nature Factory in Machida, Tokyo. OSJ Shonan Club House organizes it as a grassroots event, offering 50K and 25K distances with the same 7-hour-30-minute time limit for both. The field is small for a trail race, typically between 30 and 49 participants, and is open to adults aged 18 and over. The course follows a 4.1 km trail loop around Odo Greenery and the Sakai River headwaters; the 25K race completes this loop six times. One runner measured the 25K at 26.3 km with 2,194 m of elevation gain, describing it as: climb, descend, no flat ground. In very hot weather, the 50K route was shortened to 31 km to ensure some runners could finish. Access is also straightforward: participants take a bus from Aihara Station to Machida Nature Factory, then walk over a kilometer to the start, where the small field can converse before the race.