On July 29, 2000, Mr Chisholm, then aged 27, suffered a stroke while playing a game of rugby for the Kaikorai Rugby Club in Dunedin.
After a series of seizures he was diagnosed with locked-in syndrome, leaving his body unresponsive but all cognitive functions intact.
Despite the bleakness the prospect of a life locked-in posed, Mr Chisholm has gone on to get married, have three children and win 12 national bodybuilding championships.
"I probably would have given up fighting by now without [my family]," he said.
On the 25th anniversary of the day that changed the trajectory of his life forever, Mr Chisholm was at the gym, where he would be any other Tuesday.
He has been attending the SkyFit24 gym in Dunedin for about 23 years, and has competed in bodybuilding championships for 12 straight years.
He took home 11 wins and it got to the point where the competition asked him to stop taking part because he "kept winning".
"Well, they didn't ask me to not compete, but they kind of stopped inviting me along," he said.
He said the only year he lost was to a man who still had much of his pre-accident muscle tone.
Five days a week, Mr Chisholm is in the gym doing stretches and exercises to keep muscle tone, gain movement and to stop his body from going into a foetal position.
People often wheeled in on their first day and, sometimes, they were eventually up and walking out of the gym.
Mr Chisholm personally fundraised, via community grants and with the support of the New Zealand Rugby Foundation, to operate Iron Warriors as he saw the benefit for those impacted by life's physical and mental challenges.
He still loves rugby and on most Saturdays Mr Chisholm can be found with his lifelong friend and former team-mate Norcombe Barker attending the Kaikorai "Demons" premier games.
His friend and SkyFit24 Dunedin owner Phil Chaney said Mr Chisholm was someone anyone would be very privileged to know.
"I first met Nick years ago and he's come such a long way — where do you even start? Where he is now compared to where he was back then is ... chalk and cheese."
He said Mr Chisholm was "basically like jelly" when he first came through the gym doors 23 years ago, but these days he was able to walk assisted on the treadmill.
"His strength that he's got is incredible — for someone who doesn't walk and move, he's a real inspiration to show what you can do with hard work and determination."
Mr Chaney said Mr Chisholm’s family was "amazing, his wife Nicola is incredible and he’s got three kids ... I've seen him go through a lot ... but he’s always positive".
He believed Mr Chisholm would be at his gym until he could no longer come.
"He's part of the furniture here," he said.
