In-form Welsh runner races in the British capital on April 26 and it will be his third marathon in 20 weeks.
When Dan Osborn-Nash stormed to a big marathon PB of 2:11:49 in Seville on February 23, it was a rich reward for years of increasingly high mileage and the intelligent application of sports science.
The 31-year-old has a PhD in exercise physiology, he co-hosts a podcast called The Physiology of Endurance Running and he says he “loves the numbers”, although when it comes to racing over 26.2 miles the stats only take him so far.
“I have heart rate limits up to about 25km and then I run as hard as I can to the finish,” he says “I set myself up so I know I’m going to have a good day but then at a certain point I ignore the watch and the data and just run hard!
“I don’t care what my heart rate is 35km into a marathon! It’s going to be high and I’m going to be hurting but I have to just run as fast as I can.”
His sports science knowledge in addition to patiently nudging up his weekly mileage to its current 125 miles level has seen him knock chunks off 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 he clocked 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 now having a crack at London despite once again having only 10 weeks between races.
“I do a lab test before every marathon and before Valencia (2025) the numbers were the best they’d ever been and the training was the best it’d ever been,” he explains.
“I ran 4 x 4 miles in under 20 minutes (for each 4M rep) with a mile steady in 5:20 so I did 20 miles in 5:05 mile pace by myself 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 that he was possibly coming down with illness on race day.
He added: “With 10 weeks to Seville, I thought ‘I don’t need to be fitter, just the same shape’.”
A minor disaster struck, though, with a peroneal tendon injury halfway through his build-up to Seville, which led to a week off running and then a low-mileage week with cross training to ease back into training.
“So before Seville I’d done no big sessions and had no idea how I was going to run,” he says. “The plan was to go out at 2:15 pace and build into it. I ran 3:10 for the first kilometre and it felt pretty good. I’ve got heart rate data for all my marathons so I know what I should be running for each part of the race.
“I ended up running with Alex Milne, who came sixth in Comrades last year and has run 2:14 for the marathon and I’ve been in GB 50km teams with him twice so I know him really well and we ended up running the whole way together.”
With no pacemakers, the pair helped each other – with Milne even lending Osborn-Nash his drinks bottle – and they went through halfway in just outside 66 minutes and then closed with a quicker second half.
“We were focused but also in control. At halfway I thought we can get a 2:11 here or even 2:10 if things go dreamy.”
Endurance isn’t a big issue 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 12-14 marathons now and for the last 10 I have never blown up and pretty much executed every time,” he says. “I’ve got about a minute quicker every year since running 2:18 in Brighton in 2019 so I feel I know what works for me. But you can probably put limits on yourself when you’re looking at the numbers the whole 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, running for East Cornwall Harriers and Newquay & Par AC, although he now represents Pontypridd Roadents.
He studied biomedical science at Cardiff University but didn’t really enjoy it. A placement year at Cardiff Met in their physiology labs was more enjoyable and interesting, though, leading to a PhD part-funded by Welsh Athletics.
With funding from the universities drying up, he now works for Welsh Athletics one day a week and also does coaching for the All In running club that is run by former British 100km champion Lee Grantham.
“I have the dream set-up for my running as I work from home most days,” he says. “I drop my son off at school and go for a run and then go for another run later, pick him up and do some work in the evening.”
He is based near Newport and says the running terrain is ideal as he can find long flat trails along canal paths or plenty of hills if he likes.
“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 a running club at uni.”
In such form, it would be a dream to run in the Commonwealth Games this year in Glasgow if it weren’t for the fact the scaled-down 2026 Games does not have any out-of-stadium races.
Instead, he is focusing on trimming a bit more off his PB in London this spring.
“I bounce back from marathons so well these days,” he says. “The super shoes have an effect. I’ve been running high mileage for 15 years. I’ve done something like 12 marathons so I know I can run the next day although I’ll be a bit sore. Then 10 days later I’ll be about as fit as I was before the marathon.”
In 2020 he cheekily tweeted London Marathon organisers to suggest he could get a place on the elite start line – and it worked. But now he is fast enough to deserve one automatically.
On his limited build up to firstly Seville and now London, he says: “It’s probably not the best idea for most people as there isn’t enough time for you to improve and prepare. With the slightest hiccup you can lose a fair bit of your training block too. But if things go perfectly you can leapfrog from one marathon to another.
“By the time London comes around I will have done three marathons in 20 weeks and it’s definitely unconventional but with the super shoes and because I didn’t blow up in my previous marathons it makes it possible. The key is not to rush during 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 end up being tired before you even start a training block.”
On London, he adds: “The field looks amazing and I thought how many times will I be able to be part of a field like this? The depth of the British runners is amazing as well.”
Given his obsession with numbers, has his gradual increase in mileage been perfectly planned over the past decade? “Not really!” he admits. “It’s been more organic and more random. The marathon is pretty simple in that if you want to get better you just need to keep doing a little bit more running and a bit more intensity.”
He is also quite happy to continue coaching himself for the foreseeable future. “I’ve spent my life looking at data and then telling people how to train so I think I have to coach myself!? If someone told me what to do, I think I’d just end up disagreeing with them!
“I share my programme with people to get some suggestions but then it’s my wife Jemima who tells me if I’m doing too much, look too knackered and need to back off a bit.”
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
