When it comes to pushing his body to the extreme, one Tauranga man is an expert.
New Zealand Army trainer Staff Sergeant Alex McKenzie is a running machine and is preparing to run 200km in 24 hours, with only a five-minute break each hour.
Mr McKenzie will attempt to set the Guinness World Record for the longest grass track ultra-marathon - a record that does not exist at present.
He will race in the Relay for Life campaign next month, held for the first time in Norfolk Island. He will run 500 laps on a grass track that is being created especially for the endurance race.
While most people complete this endurance race in teams of 10 to 15 people, Mr McKenzie will tackle the challenge as a solo competitor.
"It's hard, it's very hard ... and there have been times when I've thought of quitting [in the middle of a race] but I bite my lip and find my focus again," Mr McKenzie said.
Running for 24 hours is nothing new for the endurance athlete - he has completed 200km endurance runs many times before.
Some of his feats include running around Mount Taranaki, from Palmerston North to Wellington, and from Tauranga to the Waiouru Army base, about a 250km journey.
Mr McKenzie also ran for 24 hours on a treadmill last year, raising money for KidsCan. He has also completed two Relay for Life endurance races, one in Wellington and another in Tauranga.
Mr McKenzie said he would overcome many obstacles during his 24-hour run. One of these is the need to eat - Mr McKenzie's favourite treats are crunched-up segments of Vegemite sandwiches, chocolate-covered coffee beans, jelly beans, baby potatoes and marshmallows, which he lets dissolve in his mouth.
He needs these sugary treats as he will lose about 5kg in the 24-hour run.
Another obstacle he will face is constant exhaustion and the desire to sleep, which Mr McKenzie said could be agonising.
"Your ability to stay awake is tough when you're only having short breaks, then your body starts to break down and sometimes it feels like it's too much.
"And when your body is screaming at you to stop, you need the mental focus to keep going."
Mr McKenzie attributes his mental strength to his Army training.
"It's part of the secret, being strong mentally as well as physically ... and having a great support crew."
To prepare for his 24-hour run, Mr McKenzie has been lifting heavy tyres, running up the Mount carrying heavy equipment and completing beep tests with respiratory gear on.
He runs five days a week and rests for two days. Mr McKenzie was inspired to become an endurance athlete when his 13-year-old nephew, Wayne Cherry, was diagnosed with cancer two years ago. He said it was a feeling of helplessness for Wayne that spurred him into using his running ability to help raise funds in fighting the disease.
"[Wayne is] my driving force, he's such an inspiration," Mr McKenzie said.
"When I think of all the lumbar punctures he's had and all of the treatment he goes through, what I do is so small in comparison."
The Norfolk Island race is supporting the New South Wales Cancer Society, as the island is part of Australia.
Mr McKenzie is running the race in preparation for the New Zealand Championships Ultra-Marathon Race in Auckland in October.
From Auckland, Mr McKenzie is hoping to qualify for the World Ultra-Marathon Race, held in Switzerland next year.
Mr McKenzie has only been endurance running for about four years and said it was something he never thought he would get into.
"My first long run was about 60km then the next one was 160km.
"Then I ran around Mount Taranaki and that just blew me away, I thought it was absolutely stupid because it's bloody huge," he said.
Mr McKenzie said he would continue running endurance races as long as he could.
"I'm going to make the most of my talent and continue using it to help other people," he said.
Mr McKenzie and his support team are looking for a sponsor to go on their team shirts. If you are interested or would like to make a donation, visit Smith Sport Shoes, corner Elizabeth and Grey Sts, Tauranga.