It was the promise of a skipped training session during school holidays which kick-started an Auckland trainer's fast-growing initiative, which he now hopes will help tackle two of the country's biggest problems: men's mental health and inactive kids.
Matt Giordani began the Father and Son Movement, run out of Boxing Alley gym in Auckland, when one of his clients called to say he couldn't make it into his usual weekly session.
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"He said, 'Sorry mate, it's school holidays so I can't train today,' and I said 'Nah, that's ok, bring him on down," Giordani recounted to Newshub.
"[The father said,] 'He's only 11, he can just sit in the corner with the iPad,' but I said, 'We'll get some gloves on him.'
"Well as soon as he put the gloves on, the first thing this kid did was turn around and give his dad a wallop in the guts."
The double training session was a success - Giordani's client gave him a call that night to tell him the pair had not stopped talking about how much fun they'd had that day.
It became a regular fixture in the diary, the only allocated hour Giordani's client says he gets with his son each week.
The Father and Son Movement was born.
Giordani, a father of two, says he's seen firsthand how much fitness and family time are needed after his own battles with depression.
"The thing that pulled me through was spending quality time with my kids."
He wants other parents to have the same support.
"This is allocated time with the vehicle being fitness… they're running, doing star jumps."
There's some sparring, but Giordani says he wants to make it clear there's no 'fighting' - the kids won't end up in some punch-up in the ring.
The youngest participant is four, the oldest 15. And despite the Cat Stevens-esque name, it's not just for boys - Giordani says his daughter Arabella would probably have something to say about it if it was. Daughters and mothers are welcome.
"They're just having so much fun, and the dads all have a massive smile on their face. The kids get something that they want - they get to hang out with mum and dad... They don't need expensive gifts, they don't need expensive devices… all they really want is just to hang out with us."
The NZ Mental Health Organisation says there's a growing body of evidence to show that physical exercise can be effective for people with mild to moderate depression.
"A number of studies have shown that physical activity can prevent or reduce mental health problems, mainly depression and anxiety," the organisation claims on its website.
"Studies also indicate that young people who are physically active are less likely to suffer from mental health problems. "
More information about the Father and Son Movement can be found on Facebook.