Fat Ox Endurance Runs

Event Overview

Course & Terrain

Flat concrete loop at Estrella Mountain Regional Park with central aid and personal support space.

Key course features to know before comparing this race:

• The Estrella Mountain foothills as a backdrop to every lap
• One aid station and a timing mat on every 0.988-mile lap
• A change of direction every six hours

The course is a paved walking path, nine feet wide according to USATF, looping the turf picnic area of Estrella Mountain Regional Park with the Estrella foothills behind it. It gains only about 6 ft per lap. Cones and flagging mark the route, and runners must stay outside them on the curves; cutting a curve means disqualification, though a few dirt stretches on the outside are fair game. Runners go clockwise at the start and reverse direction every six hours, at 2:00 PM, 8:00 PM, 2:00 AM and 8:00 AM. The path has no lighting, so a headlamp or flashlight is needed after dark. The 100-mile race starts 312 meters along the course.

The organizer’s guidance for race weekend in Goodyear is highs around 70–75°F and lows around 50–55°F, in what is usually a dry month in Phoenix; it still recommends layers and being ready for rain. Sunset is at 5:24 PM and sunrise around 7:08 AM, so night laps last nearly 14 hours. The 2024 championship ran under clear skies with cool to warm temperatures, according to TrailRunner.

Entry & Logistics

Why This Race Matters

Fat Ox began as an “ultra-experiment” for Nathan Coury’s college thesis on fat oxidation. Aravaipa Running first held it on November 20, 2010, as a 50K on the 500-meter dirt track at Nardini Manor in Buckeye, with Jamil Coury as race director, and it grew there into a 48-hour fixed-time festival. In 2023 it moved to a USATF-certified 0.988-mile concrete loop at Estrella Mountain Regional Park in Goodyear and began hosting the USATF 24-Hour Championships, which return on November 21, 2026. Philip Sebastiani (142.71 miles) and Janelle Stark (137.57) won the 2024 titles with the current course records. In 2025 Joelle Fenton won the 48-hour outright with 195.1 miles. The 2020 edition was cancelled.

Historical benchmark notes in the directory record (verify current records with the linked official sources):

• 48-hour men: Jerry Hughes, 228.2 miles, 2022 (set on the former Nardini Manor track)
• 48-hour women: Joelle Fenton, 195.1 miles, 2025 (first overall)
• 24-hour men: Philip Sebastiani, 142.71 miles, 2024 (USATF Championship)
• 24-hour women: Janelle Stark, 137.57 miles, 2024 (USATF Championship)
• 100-mile men: Hayden Burdge, 18:24:15, 2025
• 100-mile women: Kelly Cockrell, 18:54:05, 2025 (second overall)
• 12-hour: Georgia Porter, 75.1 miles, and Avinoam Maier, 73.6 miles, both 2025
• 6-hour: Eddy Healey, 42.4 miles, and Jaime Dawes, 40.5 miles, both 2025
• Ed Rousseau, 85, set pending US age-group records for ages 85–89 in the 100K, 12 hours and 24 hours at the 2024 USATF Championship (TrailRunner)

Preparing for a Race Like Fat Ox Endurance Runs

The 48-hour race guide covers the format as a whole. These guides go deeper:

• 48-hour races explained: Rules, pacing, sleep decisions, fueling and crew support.
• How to train for a 48-hour race: Durable movement, sleep planning, foot care and fueling practice.
• Sleep strategy for multiday races: An individual sleep plan with safe locations and clear stop criteria.
• Second-night survival guide: Sleep, crew checks and caffeine decisions for the second night.

Best Fit

• First-time ultrarunners and first 100-milers who want aid every mile and a generous time limit
• US runners chasing a national 24-hour title or automatic selection for the 2027 World Championship (145 miles for men, 130 for women)
• Runners trying their first 48-hour race on flat pavement with crew access every lap

Planning Notes

• Start conservatively and use flexible process checkpoints for effort, walking, food, fluid, alertness, and symptoms instead of forcing one hourly distance target.
• Prepare several rest options before race week. Stop for sleep or assessment if alertness, coordination, or safe decision-making deteriorates.
• Prepare for sleep decisions, weather swings, and aid-station discipline. The distance is only one part of a multi-day fixed-distance race.
• Repetitive surfaces can expose fit, friction, and loading problems. Check in when symptoms or conditions change, and use only footwear already tested for the course.
• The directory marks this as having comparatively simpler logistics. That editorial label is not a safety rating; verify cutoffs, terrain, support, crew access, and withdrawal procedures.
• The path is unlit; bring a headlamp or flashlight for nearly 14 hours of darkness.
• Cutting the inside of a curve is grounds for disqualification.
• Pacers are not allowed, so the long night laps are run alone.
• Races start on time and late arrivals cannot make up the missed time.

Event FAQs

Related Preparation

• Browse the curated 24-hour race calendar
• Browse Arizona Ultramarathons
• Compare this race in the full 2026 calendar
• Browse the 24-hour race calendar
• Browse the 48-hour race calendar
• Open the 48-Hour format guide
• Compare all race formats
• Use the timed-race pace calculator
• Plan checkpoint arrivals and cutoff buffers
• Print a pace band for your goal time
• Estimate race calories and plan fueling
• Build a crew and drop-bag plan
• Build a race-specific gear checklist