Scotty Hawker third in Ultra Trail du Mont Blanc

Ultra Trail du Mont Blanc is one of the toughest ultra marathons in the world, and it was a race Scotty Hawker almost didn't finish.

From 10km into the 171km race on August 31, the part-time Katoomba resident was struggling with sciatic and hamstring pain. He thought he'd pull out at the 81km checkpoint, but after encouragement from a friend, eventually his walk turned to a jog and he was back in the race.

"Holding my daughter Sienna's hand as we ran across the finish line together in third place at UTMB was the most unbelievable experience," Hawker said.

"Having thousands of people cheering me on and giving high fives in the final few kilometres leading into town was amazing. To cap off what was a crazy race early on and finish so strong felt so amazing."

The brutal race has 10,000m of vertical gain and 10,000m of vertical descent and includes several mountain passes. Starting at 6pm, runners only had a few hours of daylight before the added difficulties of running at night.

"It's so important to stay focused through the night, eat well and drink well. Basically for me it's trying to survive the night as best as possible so when the new day comes I'm ready to race," Hawker said.

He aimed to take in about 65g of carbohydrates per hour - mostly sushi rice balls with avocado, mashed potato balls, tortilla wraps with avocado and marmite, bananas, and then a mix of energy gels, sports drinks and chews.

It was the athlete's fourth UTMB, and he completed the race in 21 hours 48 minutes 4 seconds, behind winner Pau Capell, from Spain in 20:19:07 and Frenchman Xavier Thevenard, 21:07:56.