The Ultra-Trail du Mont-Blanc is one of the world’s toughest footraces, covering three countries, 166 kilometres and nearly 10,000 metres of elevation – all in one go.

This year, among the 2300 competitors set to take part in the ultimate feat of endurance will be Tanya Carroll, a Sydney mum and Head of Sponsorship and Marketing Services at Coca-Cola Amatil.

While Tanya has experience in ultramarathon running she said she never planned on competing in a race over 100km.

“I’d always thought ‘no, what’s the point of doing that?’ but it’s like the Tour de France for cycling, that’s what it is for ultra running.”

Like the cycling Tour, cheering spectators line the side of the road whether it’s four in the morning or four in the afternoon.

“Apparently the atmosphere is electric,” said Tanya. “People from the towns will come out at 3 o’clock in the morning ringing cowbells.”

Another drawcard is the spectacular landscape of the European Alps. “The scenery looks absolutely amazing, so I figured that’s something that will get me through some extra kilometres,” said Tanya. “Hopefully I’m lucid enough to enjoy it towards the end!”

Runners who want to compete in the gruelling event have to qualify by completing a certain number of ultra marathon races, before entering into a lottery system.

“Everyone I knew had missed out multiple times,” said Tanya. “So I thought, ‘oh yeah, I’ll throw my name in the hat’, and then fortunately - or unfortunately - I got in the first time. All my friends missed out again!”

With her spot secured and flights booked, Tanya has spent the last seven months clocking up between 80km and 130km a week in training. “Pretty much all of it is hill work,” said Tanya. “I usually do four 10km runs during the week, and 40km on a Saturday and 20km on a Sunday.”

While the fastest runners will finish the race in 20 hours, the rest of the field can take up to 46 hours to reach the finishing line. Considering half the starters drop out of the race, Tanya’s goal is simply to complete the course.

“Last year only 140 females finished and 100 of them finished in the last six hours, so [my goal] truly is just to finish,” she said. “It will be a huge accomplishment if I do manage the drag myself across the line.”

Cards with motivational messages – “I didn’t train for 7 months to pull out now!” – and breaking the race down into smaller sections are some of the strategies that Tanya will rely on to keep on going during the toughest times.

“I tell myself I could pull out at the next checkpoint, so really my race is only the next five or 10km - even though I know that I won’t pull out,” she said.

Tanya’s sister and 14-year-old son Joel will be stationed at one of those checkpoints to egg her on, while her two other children, Matisse, seven, and Jesse, five, will be at home in Sydney eagerly awaiting news of their mum’s fate.

After the race, Tanya looks forward to a holiday in Italy, and “never having to run up another hill again.”

“I keep saying to everyone that then I’m going into semi-retirement with running but it’s quite addictive,” she admitted.