⏵ Course guide · Halloween timed race, Turtle River State Park
END-TRAILS turns Turtle River State Park near Arvilla, North Dakota into a Halloween-themed timed lap race: pick a 6, 12, or 24 hour solo format, run a Skeleton Army relay with a team of up to four, or take on the single-lap Imp. I will walk you through the formats first, then give you a pacing and fueling plan built for a race measured in hours, not miles. There are free calculators along the way to dial in your own numbers.
These facts come from the official END Racing event page. Check the current year details before you commit. Race logistics can change year to year.
END-TRAILS is a timed lap race on windy singletrack with some fast, flat double track and gentle undulations, plus roughly 100 yards of pavement. The goal in every solo and relay format is the same: cover as much ground as possible before your clock runs out.
The 6-hour race runs 8am to 2pm, the 12-hour runs 8am to 8pm, and the 24-hour runs 8pm the evening before straight through to 8pm the next day. That last format means every 24-hour solo runner is out for a full overnight stretch, so headlamp management and a real sleep-deprivation plan matter as much as pace.
Teams of up to four can enter the Skeleton Army 12-Hour or 24-Hour relay, splitting the same time window across multiple runners instead of one person covering it solo. This is a genuinely approachable way to experience a 24-hour format without asking one runner to be on their feet the entire time.
If you want to experience the course without committing to a multi-hour format, the Imp is a single lap of roughly 10K starting at 2:30pm, on the same windy singletrack and double track terrain as the longer races.
The site's own benchmark treats roughly 50 miles in 12 hours as a genuinely hardcore target, which is a useful anchor for setting your own realistic goal rather than an arbitrary distance you picked in advance.
Set a lap pace you can hold for the entire window rather than banking early miles you will regret later. The windy singletrack sections in particular reward a controlled, sustainable effort over aggressive early laps.
Split your plan into a daylight strategy and an overnight strategy. Pace conservatively through the first several hours so you have genuine flexibility to slow down, fuel more deliberately, and manage alertness once darkness and fatigue both stack up against you.
⏵ Free tools to plan your effort
How you fuel END-TRAILS depends heavily on whether you are out for 6 hours in daylight or 24 hours spanning a full overnight stretch.
For the 6 and 12 hour formats, and for relay legs, aim for roughly 60 to 90 grams of carbohydrate per hour while moving and sodium in the 300 to 700 mg per liter range, adjusted for late-October North Dakota temperatures that can swing cold, especially once the sun drops on the 12-hour format.
Once you are running through the night, appetite and gut tolerance often shift, so plan a mix of real food alongside gels and drink mix, and expect to want warmer options as temperatures drop overnight. Caffeine timing also becomes a real lever for staying alert through the darkest hours.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight and your chosen format with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.
⏵ Train for it with Summit Line
Get a training plan built around YOUR fitness and the sustained, repeatable time-on-feet your chosen format demands. Summit Line reads your real training, builds the durability a 6, 12, or 24 hour effort asks for, and rehearses your fueling so race day is something you execute, not guess at.
END-TRAILS, short for Extreme North Dakota's Terrifying Run Amongst Innumerable Lost Souls, is a Halloween-themed timed lap race at Turtle River State Park near Arvilla, North Dakota. Solo runners choose a 6, 12, or 24 hour format, teams of up to four can run the Skeleton Army 12 or 24 hour relay, and there is also a single-lap Imp race of roughly 10K for those who want a shorter taste of the course.
The official race page lists the next edition for October 2026 but does not publish an exact day as of this writing. Check the official END-TRAILS page or the END Racing contact page for the confirmed date, and register early since the field is capped at 100 total runners across all formats.
Instead of a fixed distance, you get a fixed amount of time and the goal is to cover as much of the windy singletrack and flat double track loop as possible before the clock runs out. The 12-hour formats run 8am to 8pm, the 24-hour formats run 8pm the evening before to 8pm the next day, and the 6-hour race runs 8am to 2pm. The Imp is different, a single timed lap of roughly 10K starting at 2:30pm.
The course itself is not extreme, windy singletrack with some fast flat double track and gentle undulations rather than a mountain profile, and the site's own scoring benchmark treats around 50 miles in 12 hours as "a pretty hardcore" target, which gives you a sense of realistic effort levels. The real challenge in the 24-hour formats is sustained effort through the night, since the 24-hour race starts at 8pm and runs straight through until 8pm the next evening.
The 6-hour solo format and the Skeleton Army relay formats are approachable entry points: the relay in particular lets a team split the load across up to four people, so no single runner has to cover the full time window alone. The 24-hour solo format is a serious undertaking better suited to someone who has already run overnight or completed a shorter timed race first.
Fueling depends heavily on which format you pick. For the 6 and 12 hour formats, treat it like a standard timed ultra effort: roughly 60 to 90 grams of carbohydrate per hour while moving and sodium in the 300 to 700 mg per liter range, adjusted for late-October North Dakota temperatures. For the 24-hour solo format, plan for an overnight fueling strategy too, since you will be eating and drinking through the cold hours as well as daylight ones. Build your own numbers with the free ultra fueling calculator.
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<a href="https://runsummitline.com/guides/end-trails">The END-TRAILS course guide</a><iframe src="https://runsummitline.com/embed/race/end-trails" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="END-TRAILS course guide by Summit Line"></iframe>This guide is independent and for planning only. The date, formats, and course details come from the official END Racing site and can change year to year, so confirm the current specifics before you register or run. The fueling and pacing advice is general and not medical advice.
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