She's the person to befriend if you've got a moat to cross or a fortress to breach. Her career prospects are rising as fast as she does when planting her pole in the vicinity of foam mats.
McCartney cites rhythm as the most important factor to co-ordinate a quick run-up with leverage gained from using the longest pole possible.
"A lot of the effort between my coach Jeremy McColl and I goes into technical training, whether it's the run-up, the plant, swinging back or pushing and turning," explains McCartney, who was a recipient of a New Zealand Herald Future Stars of Sport award this year.
"Each needs precise work. Speed's important in transferring your energy into the air, but if you don't have rhythm, you can overstride and run under the bar."
Rio will be just the fifth time women's pole vault has featured at the Olympics. The only other New Zealand woman to be selected in the discipline was Melina Hamilton at Athens 11 years ago.
McCartney remains, to some degree, a pioneer in a sport requiring the finesse of a gymnast and power of a sprinter. She was a useful high jumper at high school before being introduced to pole vaulting at North Harbour Bays club nights.
She credits McColl, who coaches a vaulting development squad at the Millennium Institute on Auckland's North Shore, for a lot of her success.
"He puts so much effort into research. He tries to fix problems straight away or finds someone we should look at to nail [on video] a different part of the technique."
McColl has been known to personally pay for carbon fibre poles to keep his athletes internationally competitive and even built a downhill runway at the Millennium Institute to allow athletes to train at higher volume.
"The main advantage is vaulters can run off a shorter run-up and reach the same velocity [as off a full run up] to get through three to four times the amount of work," he told the Athletics New Zealand website last year.
"On the flat, a vaulter would be limited to, say, eight-12 jumps, but on the downhill runway they can have 30-plus jumps in a session."
Pole vault ranks alongside high jump and long jump as field events which captivate the most at an athletics meet.
Competitors seek inspiration from the crowd, like Russian gold medallist Yelena Isinbayeva who hid under a towel for much of the Beijing Olympics competition. She emerged each time a jump was required and, to a packed Bird's Nest's delight, eventually broke the world record.
McCartney has worked on her mental skills to cope with such dramas.
"I'm at the stage where I'm confident about going out and doing it," she says. "I had a bit of a struggle this year but overcame many boundaries due to the support around me.
"Sometimes difficulties can be hard to pinpoint and that's when you start to play mind games. A bigger pole can feel different in your hand, or you can feel further away from the mat.
"I'm lucky I've never had any major injuries. A guy I train with has snapped the pole a few times this year and ripped open his hand, causing all sorts of problems."
Studying for a Bachelor of Science in physiology also helps the first-year student adjust to the demands.
"I love the medical sciences and I hope to go down that path one day. A lot of what I learn is relevant at training. It's like a practical after class."
