Kiwi wins gruelling Antarctic marathon

From the icicles in his beard, it was clear this was no ordinary marathon.

All around, high-level climate change scientists and hardy Antarctic support workers were battling it out, fighting their way up a remote snow road on McMurdo Sound.

The scene was part of one of the hardest marathons on earth, held every year near New Zealand's Scott Base and US McMurdo Station. 

The gruelling race runs the usual length of 42.5 kilometres, pitting runners against freezing temperatures and difficult terrain.

This year, 56 scientists and support crew from both countries lined up for a tilt at the title, choosing to make the journey either on foot, cross-country skis or specially equipped 'fat bikes' that can handle the snow.

The race is held every year on Sunday, the one day of the week where staff have a day off from science.

New Zealand runner and survival trainer John Tyler described the trek as a "mental battle", saying one of the hardest elements is running in a straight line for hours on end.

There's no scenery other than snow and ice in every direction, and the terrain is so flat that runners can see the finish line from the moment they begin. 

They're forced to watch it far in the distance and can soon lose track how far they have to go.

From the start, it was clear Tyler had a chance for the title and the Kiwi, who has won every other race held at the base this season, was soon pitted against US glaciologist Max Stevens.

The two ran side by side for the entire race and Stevens, a surprise entry who had just returned from glacier work in the South Pole, put the Kiwi through his paces, running a 1 hour 36 minute half. Soon it was down to the very last kilometre.

Tyler would not be denied and made one last push, taking out the race with just 4 seconds to spare in a dramatic finish of 3 hours and 25 minutes.

Speaking through those icicles in his beard, Stevens praised his opponent for pushing through the pain.

"I thought I had him in the last while of just slowly picking up the pace, but he hung on."

Tyler, who collapsed over the line from exhaustion, returned the compliment.

"He led the charge the whole way, so definitely wouldn't have been across the line without him pulling me along."

The McMurdo Marathon living up to its reputation as one of the hardest on earth.