The Next Loop Endurance Series | Cliff Cave Park 2026

The race.

The Next Loop Endurance Series at Cliff Cave Park in St. Louis features a 3.1-mile trail loop that participants run repeatedly, starting each new loop on the hour. Runners decide after each completed loop whether to continue or stop, with no penalties for stopping and no DNF designations—only completed loops are scored. Ten loops total 50K; nine loops equal a marathon distance; four loops comprise a half marathon. An aid station is available each hour at the central base area, and results are officially timed and ranked by loops completed and combined time. The event accommodates runners of all levels, from those completing a single 5K to ultramarathon-distance participants.