Modern running history is written with heroic feats. On the weekend of November 8, 2025, the ultradistance world witnessed one of those feats when Irish athlete Caitriona Jennings won the Tunnel Hill 100 Mile in Illinois with a time of 12 hours, 37 minutes and 4 seconds, pulverising the women’s 100‑mile world record set by Camille Herron in 2017.
Caitriona Jennings’ 100‑mile world record
Jennings, from Donegal, Ireland, and aged 45, arrived in Illinois with an impressive résumé: she holds the Irish national records for 50 km (3:16:33) and 100 km (7:43:01), won the 2022 European 50 km title and has finished in the top ten of the demanding Comrades Marathon several times. She also ran the London 2012 marathon in 2:36. However, she had never tackled a 161 km race.
The Tunnel Hill 100 Mile is run on a 50‑mile (80.5 km) course that runners complete twice. The route is a compact gravel trail on a disused railway and is renowned for its speed. The race is certified by USATF and the IAU; in fact, several world records have been set on this course. Jennings held an almost metronomic pace, averaging 7:34 min/mile (4:42 min/km) with minimal variation until kilometre 120, and finished fourth overall, nearly four hours ahead of the next woman.
The silver medal on the day also went to a woman: American Anne Flower broke the 50‑mile world record, stopping the clock at 5:18:57. Flower, an emergency physician, has won races like Leadville 100, Silver Rush 50 and Javelina 100 K in the last two years. In the men’s competition, Phil Young claimed victory in 12:03:27, followed by Reese Slobodianuk (12:05:38) and Rob King (12:16:09).
Who is Caitriona Jennings
In addition to her national titles, Jennings is known for her ability to stay strong in the face of great challenges. This year she set the Irish 50 km record with 3:16:33 and continues to hold the country’s best 100 km mark. Her victory in Illinois not only confirms her versatility but shows that age is no barrier in ultrarunning: at 45, she has achieved a performance that until recently seemed unattainable.
Why Tunnel Hill is the ideal course for records
The Tunnel Hill 100 takes place on the Tunnel Hill State Trail, an unpaved track built on a former railway line. Its flat profile and compact gravel surface reduce impact and allow runners to maintain a steady rhythm. The route consists of a double out‑and‑back with a short passage through an old railway tunnel. It is sanctioned by USATF and the IAU, and some consider it both a road and a trail race because of its surface. This design, combined with well-organised aid stations, means many athletes go
there in search of personal bests.
Anne Flower’s 50‑mile record and other marks
Anne Flower’s performance at the Tunnel Hill 50 Mile deserves its own section: her time of 5:18:57 improved the previous world best by more than twelve minutes. The American averaged around 3:58 min/km and proved that speed also plays a role in extreme distances. This double women’s record joins other historic achievements on the same circuit and reopens the debate about the limits of human endurance.
How to prepare for an ultramarathon: training and nutrition strategies
Ultramarathons require more than thousands of kilometres: they demand careful planning of nutrition, hydration and physiological adaptation. The International Society of Sports Nutrition has an official position statement on nutrition in ultramarathons that summarises the science‑based guidelines:
- Moderate‑ to high‑carbohydrate diet. Around 60 % of daily calories (5–8 g/kg · day) should come from carbohydrates to avoid glycogen depletion. Limiting intake before low‑intensity sessions can improve fat oxidation, but reducing it too much compromises performance during hard efforts.
- Adequate protein for recovery. It is recommended to consume about 1.6 g of protein per kg of body weight per day, increasing up to 2.5 g/kg/day in demanding training periods.
- Caloric intake during the race. To mitigate the energy deficit, athletes should consume 150‑400 kcal/h, prioritising energy‑dense foods that provide 30‑50 g of carbohydrates per hour and 5‑10 g of protein.
- Hydration and electrolytes. Drink 450‑750 ml/h (150‑250 ml every 20 min) and supplement with sodium (>575 mg/L) to reduce the risk of hyponatraemia. Fluid needs increase in hot conditions.
- Train the gut. Practising fueling strategies in training and opting for low‑FODMAP diets helps minimise gastrointestinal problems during the race.
- Caffeine and supplements. Strategic use of caffeine in the second half of the race can improve performance, especially in events involving sleep deprivation.
In addition to nutrition, combine strength training to prevent injuries, include long runs on terrain similar to your race and plan your recovery periods. Running ultramarathons is a months‑long process, not a matter of weeks; listen to your body and, if possible, work with a specialised coach.
Upcoming ultramarathons in Spain and Europe
If after reading about Jennings’ feat you feel like pinning on a bib for a long‑distance event, here are some highlights on the 2026 calendar. Dates and routes may change, so check their official websites for more details:
- TransGranCanaria Classic (Gran Canaria, February 2026) — The island will host another edition of the TransGranCanaria with its flagship 126 km race and other distances.
- Ultra Penedès (Catalonia, March 2026) — A route through vineyards and mountains of 80–100 km.
- Ultra Sierra Nevada (Granada, April 2026) — A 100 km race along the trails of the Sierra Nevada.
- Transvulcania by UTMB (La Palma, May 2026) — One of the most emblematic races on the global calendar, with a volcanic 74 km route.
Each of these races offers alternative distances and often sells out months in advance. Start planning early to arrive well prepared.
Conclusions: the future of ultrarunning
Caitriona Jennings’ record marks a before and after for women’s ultrarunning. Her performance proves that experience and good planning can triumph over youth, and that ultramarathons are a terrain where barriers remain to be broken. If you’re a runner inspired by these achievements, maybe it’s time to set more ambitious goals. Plan wisely, nourish your body properly and let SnapRace accompany you every kilometre.