Paul Forster's heart is so strong that sometimes medical professionals double check to see if he is okay.
Years of uphill mountain running have contributed to a resting pulse rate that could suggest the Levin mountain runner needed medication.
But the 60 year old, who was last month crowned New Zealand champion in his age grade, was so fit that his base heart rate was extremely low, sometimes ambling along at 32 beats per minute.
"I did have a 28 once but that was a fluke. I am always conscious of it. What I tend to do is if I am over-tired and it is in the high 30s I try and have an easy day," he said.
When he was competing or training, a monitor showed his rate could climb as high as 160 beats per minute. He tried to maintain an average of between 140-155 beats.
"As you go further you can sustain a higher level of pulse. I work hard at it...once I get into a rhythm I try and maintain an optimum aerobic pace and sustain it," he said.
"When a nurse measured my pulse one day she said she was going to give me medication, but I just have a low resting pulse rate."
His success at the Wainuiomata event last month heralded a remarkable comeback from injury. In 2012 he was dismounting from his bike when it slide in loose gravel and he fell, hitting the ground hard.
"I had my foot in the pedal and couldn't get it out and the wheel went from under me. I couldn't get up and had to have an ambulance pick me up.
He required surgery on both hips. The most recent was just 18 months ago, leaving him unable to train or compete as he recovered.
"That's why this medal means so much. It's been 10 years since the last one and I didn't know in the early stages if I could achieve what I used to achieve," he said.
"I just love running up hills," he said, and his training attested to it. One month he clocked up 4km of altitude climbing.
His sport has taken him all over the world. Originally based in Wellington, he had represented New Zealand in uphill running at events in Italy, Austria and Germany when he was in his 20s and 30s - six world events in total.
He was still good enough at 42 to make the New Zealand senior men's team.
Forster said Kohitere Hill to the east of Levin was a perfect training ground and had good gradient of "about 10 or 11 per cent", and he used it as part of an 18km training circuit.
He said his injury was hard on his partner at the time too, as they were booked to fly to Australia the next day and had their holiday plans axed.
Now, whenever they plan for a vacation, he moved carefully in the weeks prior.