Growing up, she avoided athletic activities. ‘‘I wasn’t very sporty,’’ she says. ‘‘I didn’t partake in sport when I was a kid, and I think I missed out.’’

After she had children, the former engineer – now a teacher at Montmorency Secondary College – decided to hit the gym to shed unwanted kilos.

‘‘I felt like I needed to get a bit fitter, as I’d put on a lot of weight since university and work,’’ she says.

Once she joined the Eltham Leisure Centre, she started taking spin classes, running on the treadmill and swimming.

Zerbe also wanted to teach healthy habits to her children – six-year-old daughter Corine and three-year-old son Ryan.

‘‘I wanted to set an example. I could see how other people went the other way after having children. But I wanted to keep my kids fit and be able to keep up with them.’’

In 2009, she competed in a mini-triathlon consisting of a 250-metre swim, a 10-kilometre bike ride and a two-kilometre run.

She came third last, but managed to finish while several other competitors had to be plucked from choppy waters.

‘‘I was terrible, but it made me want to get better, because it was such a poor effort.’’

Now, Zerbe exercises four or five times a week and has competed in five triathlons.

When BNW spoke to Zerbe last week, she was preparing for her toughest triathlon yet – the Omara Cycles Women’s Triathlon, comprising a 400-metre swim, a 16-kilometre bike ride and a four-kilometre run.

Zerbe entered the event, held last Sunday, for a cause.

Last year, her best friend Nerida was diagnosed with ovarian cancer, a rare but aggressive cancer. ‘‘It was such an awful shock. She is just 34, and she has a husband and a one-year-old son,’’ says Zerbe. ‘‘We were bridesmaids at each other’s weddings.’’