An in-form Welsh runner will run in the British capital on April 26 and it will be his third marathon in 20 weeks.
When Dan Osborn-Nash achieved a great marathon PB of 2:11:49 in Seville on February 23, it was a great reward for years of increasing mileage and the intelligent application of sports science.
The 31-year-old has a PhD in exercise physiology, co-hosts a podcast called The Physiology of Endurance Running, and says he “loves numbers,” although when it comes to races longer than 26.2 miles the statistics only take you so far.
“I have heart rate limits up to about 25km and then I run as hard as I can until the end,” he says. “I prepare myself knowing I’m going to have a good day, but then at a certain point I ignore the clock and the data and just run hard!
“I don’t care what my heart rate is at 35km into a marathon! It’s going to be high and it’s going to hurt, but I have to run as fast as I can.”
His knowledge of sports science, as well as patiently increasing his weekly mileage to his current level of 125 miles, has allowed him to significantly reduce his marathon PB.
In 2016 he ran 2:27:43 in Manchester but by 2018 he had improved to 2:18:53 in Brighton. Further improvements followed before clocking 2:13:02 in Valencia in 2024 and then 2:14:03 in the same Spanish city in December last year. Then just 10 weeks later, 2:11:53 in Seville this year before, I now have a shot at London despite again only having 10 weeks between races.
“I do a laboratory test before each marathon and before Valencia (2025) the numbers were the best and the training was the best of all,” he explains.
“I ran 4 x 4 miles in under 20 minutes (per 4M rep) with a steady 5:20 mile, so I did 20 miles at 5:05 mile pace feeling good, so I thought ‘I’m going to run 2:10-11 in Valencia,’ but I ran 2:14 and got sick the next day,” he adds, suggesting he would possibly get sick on race day.
He added: “With 10 weeks in Seville, I thought: ‘I don’t need to be in better shape, just the same shape.'”
However, minor disaster struck with a peroneal tendon injury halfway through his preparation for Seville, leading to a week of rest and then a week of low mileage with cross training in order to get back to training.
“So before Seville I hadn’t done any big sessions and I had no idea how I was going to race,” he says. “The plan was to go out at a 2:15 pace and build it up. I ran 3:10 for the first mile and felt pretty good. I have heart rate data for all my marathons, so I know what I should run for each part of the race.
“I ended up running with Alex Milne who came sixth at Comrades last year and ran 2:14 in the marathon and I’ve been on GB 50km teams with him twice so I know him really well and we ended up running the whole way together.”
Without a pacemaker, the pair helped each other (Milne even lent Osborn-Nash his drink bottle) and reached the halfway mark in just 66 minutes and then closed with a faster second half.
“We were focused but also in control. Halfway through I thought we could get a 2:11 here or even a 2:10 if things go dreamy.”
Resistance is not a big problem for Osborn-Nash. In 2019 he broke the British 50km record in Romania with 2:49:01. He also has confidence in what the numbers tell him.
“I’ve run 12 to 14 marathons and for the last 10 I’ve never exploded and I’ve executed pretty much every time,” he says. “I’ve gone about a minute faster every year since I ran 2:18 at Brighton in 2019, so I feel like I know what works for me. But you can probably set limits when you look at the numbers all the time.”
Osborn-Nash was born in New Zealand but moved to the UK at an early stage and grew up on Bodmin Moor in Cornwall, racing for East Cornwall Harriers and Newquay & Par AC, although he now represents Pontypridd Roadents.
He studied biomedical sciences at Cardiff University, but didn’t really like it. However, a placement year at Cardiff Met in their physiology laboratories was more fun and interesting, leading me to undertake a PhD partly funded by Welsh Athletics.
With university funding running out, he now works one day a week for Welsh Athletics and supports the All In Run Club performance training programme, run by former British 100km champion Lee Grantham, specializing in physiological testing and pacing strategy.
“I have the ideal running setup since I work from home most days,” he says. “I drop my son off at school and go for a run and then I go for a run again, pick him up and work a little at night.”
He lives near Newport and says the running terrain is ideal, as you can find long, flat trails along canals or lots of hills if you want.
“I came to Cardiff Uni in 2012 and never left,” he says. “I live here, married a Welsh girl and have a four-year-old son who was born in Cwmbran. My wife also runs as we met at an athletics club at university.”
In this way, it would be a dream to participate in the Commonwealth Games this year in Glasgow if it were not for the fact that the reduced Games of 2026 do not have races outside the stadiums.
Instead, he’s focusing on cutting his PB a little further in London this spring.
“Nowadays I recover very well from marathons,” he says. “Super shoes have an effect. I’ve been running high mileage for 15 years. I’ve done about 12 marathons, so I know I can run the next day even though I’ll be a little sore. Then 10 days later I’ll be as fit as I was before the marathon.”
In 2020, he cheekily tweeted at London Marathon organizers to suggest he could get a spot on the elite starting line, and it worked. But now it’s fast enough to automatically deserve it.
Of his limited preparation first to Seville and now London, he says: “It’s probably not the best idea for most people, as there is not enough time to improve and prepare. With the slightest setback, you can also lose a good part of your training block. But if everything goes perfectly, you can jump from one marathon to another.
“By the time I get to London I’ll have done three marathons in 20 weeks and it’s definitely unconventional, but with the super shoes and not blowing up in my previous marathons, that makes it possible. The key is not to rush through the build up even though I have another marathon in 10 weeks. It’s important to recover from the marathon before you start training for the next one, otherwise you’ll end up tired before you even start a training block.”
On London, he adds: “The field looks incredible and I thought how many times will I be able to be part of a field like this? The depth of the British riders is also incredible.”
Given your obsession with numbers, has your gradual increase in mileage been perfectly planned over the last decade? “Not exactly!” admits. “It’s been more organic and more random. The marathon is pretty simple in the sense that if you want to improve you just need to keep running a little harder and a little more intensity.”
He is also very happy to be able to continue training himself for the foreseeable future. “I’ve spent my life looking at data and then telling people how to train, so I think have To train myself!? If someone told me what to do, I think I would end up disagreeing with them!
“I share my program with people to get some suggestions, but then it’s my wife Jemima who tells me if I’m doing too much, if I look too exhausted and if I need to back off a little.”
Marathon Progression
2016 2:27:43 Manchester Marathon
2018 2:22:55 Brighton Marathon
2019 2:18:53 Brighton Marathon
2021 2:29:12 London Marathon
2022 2:15:34 Manchester Marathon
2023 2:15:22 Valencia Marathon
2024 2:13:02 Valencia Marathon
2025 2:14:03 Valencia Marathon
2026 2:11:53 Seville Marathon
