AFTER facing Arctic conditions and blistering heat to run on all seven continents of the world you might think there were few feats left to tackle.

But ultra-runner Shona Thomson has completed her greatest challenge yet - racing 26 miles along the frozen River Tuul Gol in Outer Mongolia.

Despite numerous setbacks during her training, the ambitious Scot conquered a marathon on a route no one had ever stepped foot on before.

Shona said: "It can be easy to overthink challenges such as these but at the end of the day it is only an extremely cold run in Outer Mongolia.

"There are so many new variables for your body to cope with from the jet-lag to the food to staying in Gers with local nomads to the bitter cold.

"It is impossible to predict what will happen on the day or how your body will react to the cold.

"In some ways, these types of marathons are less pressure than conventional marathons as it is very hard to target a time when you're running in minus 40 degrees Celsius on ice.

"For me, the main competition is the conditions: the risk of frostbite, hypothermia and the local wolves."

The route was so precarious that runners had to be protected from local bears by husky dogs, which ran alongside them.

Extreme cold also posed particular problems.

Shona said: "We were supported by huskies patrolling the course to ward off the wolves and bears in the area.

"Water turned to ice in minutes so staying hydrated was a real challenge.My gels became increasingly hard to swallow as they began to freeze.

"I also used up a few more than I normally would as my body worked to keep warm and deal with the underfoot terrain.

"I took a wrong turn at one point - as did several other runners - and headed out onto the vast plains. I felt the complete isolation and remoteness of the area.

"I’m not sure how much further I ended up running but I didn't mind as the landscape was just so breathtaking."

Shona, from Craigmaddie, added: "The temperature outside was minus 40 degrees Celsius, the winds are bracing, the ground hard with ice, yet the sun shines, reflecting off snow-capped mountains and sparkling on the frozen river.

"It is bleak but it is beautiful. This was the backdrop of our 26.2 mile run along the frozen river Tuul and winter wonderland of wooded trails.

"It's much harder to breathe in such temperatures and there is always a danger of hypothermia and frostbite.

"I kept at a steady pace so that I could safely monitor my body, plus I was under under orders not to get my heart rate up due to my iron levels.

"My breathe froze on my balaclava and formed a frozen armour against my face. My eyes watered, creating crystal visors on my eyelashes.

"At times, I thought I was passing through Dante’s ninth circle of hell, frozen in the ice lake of Cocytus, as I became progressively encased in ice."

Shona added: "After several hours out in the Mongolian wilderness, I made it to the finishing point, at a local Nomad’s Ger. I was a bit bruised from taking a few tumbles on the ice.

"Probably the greatest damage was to my earlobes as I stupidly forgot to remove my earrings. They got quite severe frostbite which began to blister, bleed and turn black.

"However, the medics were top class and got me on antibiotics straight away."

Organised by expedition leaders, Sand-baggers, the Genghis Khan Ice Marathon was being run for the first time.

The team of nine included experience polar runner Dr Andrew Murray, from Edinburgh, who went on to run 100 kms through the Mongolian wilderness just 24 hours later.

Shona was competing in order to raise funds for Riding for the Disabled (RDA) and the Scottish Association of Mental Health (SAMH).

For Shona, who is an investment banker, the two charities were the spur to keep her going when the race felt particularly tough.

She also rode a Mongolian pony to help raise awareness of RDA.

Shona said: "I think first and foremost it is about the team and support network. To undertake a run like this is not so much about ability, it's about mental attitude.

"Most importantly, it’s about having a sense of perspective.

"It is only a day of running in the extreme cold, which is nothing when you think about the challenges faced by the ill and disabled on a daily basis, like those for whom we are fundraising."

Anyone who would like to donate can make a gift at uk.virginmoneygiving.com/team/GhengisKhanIceMarathon

Or to find out about taking part in next year's event, see visit www.sand-baggers.com