For the three Singaporeans who finished the North Pole Marathon, the event was more than just a race.

It was an adventure with extreme weather conditions, sudden changes in flight plans and injuries.

Last week, they gave The Sunday Times more details of the eventful lead-up to the race, which they completed on April 17.

Ms Gloria Lau, 64, who covered only 28km in last year's race, ran the full 42.2km distance this year and finished in 11hr 30min.

She was the oldest of the 11 female runners and became the first Singaporean woman to finish the full North Pole Marathon.

Mr Ong Tze Boon, 47, group executive chairman at environmental design solutions firm Ong & Ong and son of late president Ong Teng Cheong, finished the race in 6hr 40min.

His cousin Ong Yu-Phing, 47, an IT director, finished in 9hr 4min .

The race was scheduled to start on April 9, but there were cracks on the runway - an ice sheet in the Arctic Ocean - so the Singapore runners' flight from Svalbard in Norway was delayed until April 14.

A second plane carrying the rest of the marathon runners was also forced to turn back just 15 minutes before it was due to land when another crack appeared .

"The greatest thing plaguing my mind in this whole event was the stress over the second group not being able to arrive," said Ms Lau.

"With all those runway cracks and repairs, we thought we would be stranded (in the Arctic Ocean) indefinitely, not even being able to do an official run."

Mr Ong Yu-Phing added: "The delays, the crack that appeared less than 5m from our tent within five hours of arriving in the North Pole camp - and that crack delayed our race by another 24 hours and extended our stay there - all these really made it an adventure and not just a marathon."

The race finally began after all 47 runners arrived, in temperatures of around minus 35 deg C.

Photos on the event's Facebook page show runners with snow on their eyebrows, eyelashes and beards. Many of them had goggles but some of these fogged up in the cold and could not be used.

Mr Ong suffered mild hypothermia about five hours into the run, and spent about half an hour warming up in a tent before continuing.

He also injured his right knee when he slipped after running for about 20km, and had to walk for most of the second half of the race.

The terrain was also challenging. While the first 32km had mainly hard packed ice, making it an easier surface to run on, the last 10km required runners to run on soft ice.

Ms Lau said: "I had severe calf muscle cramps. It is quite difficult to distinguish the depths of snow, even when trudging through slowly. I could hardly walk for a couple of days after that."

All the Singaporean participants ran for charity. Ms Lau, who runs a property development business, had said people can tell her which charity they want to donate to, and she will match the amount dollar for dollar. She declined to say how much she raised.

The Ong cousins hope to raise funds for five mental health charities, including the Singapore Association for Mental Health. They have raised about $200,000.

This includes $25,000 from their firm's philanthropic arm, Ong Foundation, and $8,000 from personal donations from the cousins and Ong & Ong staff.

Ms Lau added: "Everything culminating to finishing this race is just a massive, euphoric wave of pride and relief that I did it."