"They said, ‘You old git, what are you doing that for?’"
The 48-year-old will step into the ring this weekend with Chace Martin (31).
However, Mr Jarvis does not think his extra years on the planet will be a disadvantage.
"Not really. I think if the fitness is there then age doesn’t make really that much difference. If it wasn’t, I’d be slightly more worried about it."
Mr Martin, who is from Rotorua, agreed and described his opponent as stronger than him.
He has lived in Queenstown for two and a-half years and signed up as a challenge to get fit.
Prior to Thriller he was not a gym junkie and his exercise regime amounted to the odd walk or hike.
Mr Jarvis started going to the gym a couple of years ago to get fit enough to enter.
The pair have a healthy respect for each other and have trained and sparred side by side. They are two of 18 competing in the event after a 14-week training camp led by head coach Steve Orr.
Training is tough and Mr Orr said the competitors had improved dramatically since starting out.
"There’s a very diverse ability across the group — people progress at different rates, have plateaus. Some break through, some don’t.
"We taught them footwork but then got them sparring really early so they got used to the contact. A lot of them were very gun-shy.
"We keep everything simple, basic. It’s not how we’d teach people who’ve got longer to learn but we’ve found this is the best way to get people to a level where they can have a good contest."
Mr Jarvis, who is originally from England but lived in Arrowtown for 18 years, is not nervous about the fight.
"You are getting in there and doing a sport. It is not like we are going in to kill each other."
The 2017 Thriller event is being held at Queenstown Events Centre, on Saturday and doors open at 6pm.
It is a fundraiser for Branches Charitable Trust.
This year, it will feature, for the first time, an amateur bout between New Zealand’s number one and two light welterweight fighters Richie Hadlow and Sam Burdett-Clark, who comes from Queenstown.
The last time the two met, Hadlow was the victor.
