Rocky 50k Fat Ass Run

Rocky 50k Fat Ass Run is an ultra held in Philadelphia, Pennsylvania, on December 5, 2026, with a single distance, 50 km (about 31.1 miles), starting at 7:00 AM. The early start gives you the full winter daylight window to work with, which matters at a distance that will keep most runners out for five hours or more.

Stepping up from the marathon to 50K is less about speed than about time on your feet and a fueling plan you have actually tested. Build over 14 to 16 weeks with a weekly long run reaching four to five hours, and use back-to-back weekend runs to teach your legs to work when tired. Plan to eat something every 30 to 45 minutes from the first hour, not once you feel empty. Run the opening 10 km slower than feels natural; on a December ultra, the finish is decided in the last two hours.