The 28-year-old told BBC Sport she had performed 10 sessions of up to 90 minutes each at the physiology department of St Mary's University, with two more remaining. The method in this madness is to avoid wilting in Friday's women's marathon at the World Championships in Doha, which is scheduled to begin a minute before midnight.

Doha's furnace-like daytime conditions - which regularly top 40C - meant organisers had little choice but to start the women's and men's races as late as possible. However, the Hampshire athlete still expects 60% humidity and for temperatures to range from 33-36C, which is why she made use of the services provided by the London university.

"The lab monitored my heart-rate, body temperature and sweat-rate, and based on those values we worked out if I was adapting to the heat - it's so far, so good," Purdue said before heading to Great Britain's training camp in Dubai.

"After the first session I thought I'd never be able to do this, but I quite like it now."

Coached by Australian Nic Bideau, the former European cross-country champion is currently in rude health after a torrid 2018. Injury forced her to withdraw from the London Marathon, then she suffered cramp in a race at the European Championships and that was topped off by a virus which effectively ended her year.

In contrast, 2019 saw her become the third fastest British female marathon runner, win the London half marathon and follow that up with a fifth place at the Great North Run, where she knocked a minute off her personal best.

Unsurprisingly, Purdue sounded ebullient.

"I came off two big build-ups, but didn't run the marathons, so it's not such a shock that I got into good shape again," she added.

"I'm glad it's gone better for me this season - looking back on what happened it's worked out pretty well."

The Briton is optimistic of finishing higher than the 13th she managed two years ago in London, and Doha's marathon course might aid her in her mission.

"It's six 7km loops of the Doha Corniche," she said. "It's flat so it could be quite a fast course, although if it wasn't so hot then it'd be a rapid course.

"The good thing is I love doing loads of loops. Anybody who know me from training camps knows I like loops."

Dundee-born Eilish McColgan competed at the 2012 and 2016 Olympics

The events inside the refurbished Khalifa Stadium have also been scheduled later to factor in the weather. Unlike previous World Championships, there are no morning sessions, with the competition starting after 16:00 local time, at the earliest.

Purdue's team-mate Eilish McColgan, who will be competing in the 5,000m and 10,000m, is not worried about the heat affecting the athletes because of the air-conditioning system that will operate inside the venue. This was implemented at the Doha Diamond League event in May.

The Scot, whose mother Liz - the 1991 10,000m world champion - coaches children in Doha, told BBC Sport: "People shouldn't freak about it too much. The temperature will probably be regulated from the low to mid 20Cs. We were running in 30C during the recent British Championships in Birmingham.

"That's why a lot of the athletes have been preparing in high altitude in Switzerland or France because they realise the stadium will be air conditioned.

"I was speaking to Qatari high jumper Mutaz Barshim who said he found it quite cold because there were constant jets of air. Of course, for us running we won't feel that."

McColgan, 28, also passed on advice to those planning to train outside the stadium: "I've been running in public parks because the roads are chaos.

"You also have to make sure you're covered appropriately in order to respect the culture and religion. I make sure I wear longer shorts or three-quarter length leggings, and I'll always wear a T-shirt."

Purdue will line-up for the women's marathon at 21:59 BST on Friday and McColgan begins her campaign with the 10,000m final on Saturday at 19:10 BST.