When Caitriona Jennings of Ireland set a new women’s 100-mile world record at the 2025 Tunnel Hill 100 Mile with a time of 12:37:04, it was her first time running the distance. She broke Camille Herron’s old mark of 12:42:40, which she set at Tunnel Hill in 2017.
We caught up with Jennings two days after her run. She’d already flown home to Ireland on an overnight flight, taken a quick nap at home, and was back to work in the office on Monday morning. In her first interview with iRunFar, Jennings talked about her background in running, her decision to try the 100-mile distance after a decade of running 50k to 90k events, how she paced her effort and stayed positive when things started to hurt, and what it was like to cross the line with a new world record in hand.
Jennings also talks about what it was like to share the course with Anne Flower, who set a new women’s 50-mile world record at the Tunnel Hill 50 Mile, and Courtney Olsen, who set a new women’s 100k American record. You can learn more about Anne’s run in our post-race interview with her.
Caitriona Jennings with a new women’s 100-mile world record. Photo: Micki Colson/Colson Photography
[Editor’s Note: The following interview has been lightly edited for clarity.]
iRunFar: It’s two days after your world record run at the 2025 Tunnel Hill 100 Mile. First off, congratulations! That’s a massive run. How are you feeling? How was your flight back home to Ireland?
Caitriona Jennings: I’m feeling surprisingly well. Immediately after the race, I was so tired and my legs were really shot. I was struggling to walk, but I’m actually moving around okay today. My flight overnight was nice, and then I managed to do a 30-minute cycle into the office this morning. So, I think that helped just get the blood flow a bit and no pounding or any sort of impact on the legs. That was nice, and I think it’s helped a lot.
iRunFar: Did you at least get premium seating on the flight?
Jennings: No, but it was an empty flight, so I got four economy seats, so I was able to lie down, which was amazing. I had a whole row to myself.
iRunFar: Amazing. Starting off, this is the first time iRunFar has done an interview with you. I’d love to hear more about you as a person, as a runner. You’re the 50k, 50-mile, and 100k Irish record holder. You’ve been top 10 at the Comrades Marathon four times. I believe you’ve come to the U.S. to race a handful of times since 2017. How would you describe yourself as a runner and as a human?
Jennings: So I guess athletics and sport have been a huge part of my life since I was very young. I started off as a triathlete and represented Ireland at a junior level. About halfway through my university degree, and when I moved to Dublin to start my professional job, I just really focused on the running side of things because it was just more time efficient and I really enjoyed the run probably more than the other two disciplines.
Then I represented Ireland in a couple of world championship events. I was in the World Championships Half Marathon in 2010 and then the Olympics in London in the marathon in 2012. Then following that, about three or four years later, I kind of started dipping my toe into the ultra world. I think I did my first 50k World Championships in 2015 in Qatar, and that’s where the ultra journey started. I kind of got hooked.
I used to, at the start, say that I much prefer the marathon, that it was always the distance that I loved the most. I was quite passionate about marathon, and I felt that was my discipline. So when I was transitioning to ultra, I had to shift my mindset a little bit, but now that I’m fully absorbed in it right now, I’m really really enjoying it. I like how there’s more skills in ultra, in that you need to use your mental preparation I’d say as much as your physical preparation. Every race always just produces something completely different, and you just don’t know what to expect. You really have to think on your feet and adapt along the way, so I really enjoyed that part of it as well.
iRunFar: This was your first time racing 100 miles. What was the motivation to step it up to that distance?
Jennings: I had just finished Comrades in June, and I hadn’t really a plan for the second half of the year because I typically like to just focus on one race, and not for too far ahead, and Comrades this year was my “A” race. So when I sat down after Comrades with my coach Terry McConnon, I just decided I wanted a new challenge and something that was really going to push me and maybe question even whether I had the ability to do it. And I thought the 100-mile distance was a nice distance. It intrigued me how I would go. I suppose the unknown of how I was going to go from the 100 kilometers up to the 100 miles was kind of exciting. It was a little bit exciting, a little bit terrifying. But I just decided, “Yeah, let’s do this and see how it goes.” And if it goes terribly, then at least I’ll know. I don’t do it again, but if it goes, it would be great.
I chose Tunnel Hill because I knew from just reading about it that it’s a really good course for fast times and I thought I may as well make it as easy for myself as I can by choosing a good course and a flat course for my first 100 miles.
iRunFar: You said you wanted to move up to the 100-mile distance, but was there any motivation to race the Tunnel Hill 50 Mile?
Jennings: I would have liked to, but for some reason I think at the point in time when I decided to run the 100, I needed to challenge myself in a different way because it’s not that I was getting sick of training, but I felt that training was becoming a little bit too competitive, too repetitive, and I needed something to challenge me to just push me outside of my comfort zone and to excite me again. I was still enjoying racing, but I wanted something to just shake it up a little bit.
iRunFar: How did your training change compared to what you’ve been doing?
Jennings: I increased my weekly mileage, and I also increased my two long runs at the weekend. They were the two key changes. I suppose when you’re training for 100 kilometers, your long run, it obviously needs to be long, but I really felt that I needed to be running for probably cumulatively between six and eight hours on the weekend between Saturday and Sunday so that I was getting that repetitive pounding in my legs. And then also just adding in additional sessions during the week where I could find the time, whether it be a run or a gym session or something, just to make sure that I had the time and the feet and that I knew that my legs would be strong to get me through on the day.
iRunFar: Going into Tunnel Hill, was a world record always in mind? Was that the goal?
Jennings: I would say it was my A goal. I thought I would really love to give it a shot. I had no idea whether or not it was possible. So I kind of had an A goal, a B goal, and a C goal, because I figured that you’re going to be on a course for so long, that if A goal isn’t going, I didn’t want it to be just a write off. I wanted to still enjoy the day and enjoy the experience and try and make my first 100 mile at least somewhat fun so it wouldn’t put me off completely. The Irish record for the women was 16:38, so that was my C goal. The Irish record for men was 13:18. So I thought that’d be nice to get the best man’s record in Ireland. And then A goal was the world record. So, kind of depending on how things went on the day, I felt if I achieved one of those, I’d be happy.
iRunFar: Your pacing for the first 80 miles was essentially unchanged, like you were nailing that pace. Was that a predetermined “I want to try to run this pace” or was that just by feel?
Jennings: No, I actually wanted to run slower. I intended to go out slower but I just couldn’t slow myself down. I was trying so hard to be patient, to be disciplined, and to be as relaxed as I could, but it was an unnatural feeling for me at that point of the race to run so slowly. So I had to run a little bit faster just to feel comfortable and get into the rhythm and hold that pace. And also, just looking at my heart rate during the race, it was still quite low. It was low zone three, and I was very comfortable that I wasn’t burning any reserves at that level of running. So I just decided, “I feel really comfortable on this pace. I feel more comfortable in this pace than I do on my goal pace. So I’ll just stick with this and see how it goes and see if I can hold it.” And then maybe allow for some attrition. I just got into a really nice rhythm and held it well. The course does lend itself to even pacing as well because it’s a nice flat course, which obviously helps.
iRunFar: How did you feel throughout the various parts of the course? Were there any high points or low points, or points when you felt things were maybe going downhill for a bit?
Jennings: Yeah. I mean, I really enjoyed the first maybe hour or two, where there were a lot of 50-mile racers around me. I was watching, I was really looking forward to the turnaround where I could see the lead men for the 50 mile and the lead women for the 50 mile and the lead women for the marathon. Courtney Olsen was running the 50 mile [Editor’s note: Olsen raced the 100k and received an intermediate 50-mile split time], and I was really excited to see how she was going. Also, Allison Mercer was running the marathon, and both actually set course records. Courtney obviously set the American record for the 100k, which was amazing and brilliant for me to actually observe on the course.
When I was getting all this information — I saw a little bit of it, but my husband, who was crewing me, was also giving me information about how the girls were running — and that really gave me a huge lift as I was running through. So that was probably the first 50 miles, and then the course on the next out-and-back, just after 50 miles, was really lonely. There were very few people on the course at that point, and that was getting to the point where it was new territory for me as well, because I’d never run more than 60 miles.
It got hot during that time of the day, too. I kind of started going, “Okay … mmm,” but at the same time, I was confident that I was still feeling good. And I just kept reminding myself, “Yes, okay, this is where it’s going to start hurting, but you’re still feeling good.” And that was fine until I came back to Vienna, which was the point where you made your last out-and-back until to the finish. And I think that was probably then where I really knew this was kind of the make-or-break time, the next 24 miles. I was still on pace, I still had a buffer, but I was like, “Right, this is where it’s going to either I’m going to make it or break it.” But I had a really positive mindset. I think I had no expectation. I had no pressure. It was all going to just be a positive. So I feel like that all helped, and it helped me to keep a very positive mindset even when it did start getting a bit tougher in that last 24 miles.
iRunFar: Was there a point where you felt confident that you’d get the record?
Jennings: Honestly, I was getting more confident the closer I got to the finish line, but I knew that anything could happen, and I wasn’t sure. It was all so much of an unknown. I didn’t know if maybe my legs would just go on me, and maybe I’d start cramping. There were just so many unknowns that I was never confident that I was going to actually definitively get it until the last checkpoint, 2.8 miles from the finish. And I was like, “I think I can probably get it now.” But you really just need to cross the finish line to secure it in that situation. That’s why I was just so happy to finish, to get over the line and just have it done and in the bank.
iRunFar: What was that crossing that finish line, knowing that you’d gotten the record?
Jennings: I was emotional. I have to say, I don’t know if it was the tiredness from just being on your feet all day or what, but I felt it slightly overwhelming. Just that sense of “I did it” was quite emotional.
iRunFar: And what was it like to break a record set by Camille Herron, who’s such a legend of our sport? What does that feel like?
Jennings: Incredible, to be honest. I have so much admiration for her. I think she’s set so many records across so many different races and distances throughout the ultra world. And they’ve stood for quite a while. I really felt honored to take that record. And I feel like she has really just upped the game for everyone, because she’s shown everyone else what’s possible. And when you see it, you can start making it more achievable for yourself. So, I mean, absolutely kudos to her. And I wouldn’t be surprised if she’s back out there very soon to take it back again, which would be fun.
iRunFar: My last question. I never want to phrase this question as “What’s next?” especially because you’re two days out from doing this, but how do you think this win and this record is going to change your outlook on running going into the future?
Jennings: I think it’s really opened my mind to distances above 100k. I was very much of the mindset that anything over 100k was crazy. I think it’s a completely different type of experience and race. I don’t know if I could do it too often because I do think that you need to be incredibly well-prepared for it, and you need everything to go right for it to go well on the day. But, I think I will definitely look to see, I might challenge myself in different types of races that I wouldn’t have previously thought of doing. And maybe just trying to have more fun with it and challenging myself.
I really felt like I enjoyed the build-up to this race because it was different, because it was new, and I’d like to kind of keep that going and see where that brings me.
iRunFar: Congratulations on your world record. It was amazing to watch such a well-executed race, and I hope you recover well.
Jennings: Thanks so much.
Caitriona stopping the watch on her new women’s 100-mile world record. Photo: Micki Colson/Colson Photography
