Shortly afterwards a friend started vaulting and Eliza, too, took the plunge. Aged 13 at the time the North Shore-based enjoyed her first ever session coached by Jeremy McColl - the man who has guided her every step of her pole vault adventure.
Initially working on basic drills, it was only after several sessions did she bend the pole for the first time. The experience came as a surprise.
"It was a shocking feeling, because you feel out on control," she comments.
Yet the Aucklander was not discouraged and three months after taking up the event, Eliza overcome intense nerves to successfully clear 2.40m on her competitive debut at Mt Smart Stadium.
Less than a year after taking up the sport she vaulted 3.40m to take the 2011 Australian Junior Championships. The following year she grabbed the New Zealand Secondary Schools' Championships in Dunedin with a best of 3.85m.
Competing as a rep level netballer for North Harbour she faced some big choices. Her coach had spoken of targeting the 2013 World Youth Championships in Ukraine and after some deliberation she opted to quit netball to focus on her growing passion for athletics.
"I thought I had more opportunity with athletics than netball," she says. "There was a clear pathway in athletics. It was a hard decision, but it made sense at the time."
In 2013 she continued to make rapid progress. At the Auckland Schools Championships she leapt a PB of 4.11m and qualified for the IAAF World Youth Championships in Donetsk - a competition which was to prove pivotal in her career development.
In Ukraine she finished fourth with a best vault of 4.05m, but was enriched by of her first global championships experience.
"I definitely learned some things about how to compete in a big event," she says. "I remember during warm up people were pushing and shoving on the runway to get as many warm up jumps as possible. I know I didn't get as many warm-ups as I typically would, but the World Youths taught me many little tricks about how to compete in a big competition overseas."
Her 2014 campaign was bedevilled by injury and illness as a combination of glandular fever and shin splints derailed much of her domestic season. Eliza missed out on her goal of qualifying for the Commonwealth Games in Glasgow, yet having already achieved the qualification mark for the World Junior Championships in Eugene, Oregon she still had a goal to work towards.
Her coach switched her programme around and replaced running (which she was unable to do nursing shin splints) with cycling and indoor rowing to maintain her fitness levels. She received fantastic support from her physio and the Devonport-based athlete made it to Eugene.
There she shrugged off the distractions of a challenging build up to vault a PB of 4.45m to take the bronze medal. It proved a critical moment for Eliza.
"It was huge for me (winning bronze) and from that point in my life a whole new world opened up," she says. "It wasn't the smoothest competition, but I really kept pushing for that medal. I didn't want to finish fourth again."
Possessing a steely determination and resilience Eliza clearly has many of the attributes of a champion. However, she has faced her struggles and like many of us needs occasional help and support.
That was nowhere more apparent than in 2015 when she suffered a "mental block" for some months which prevented the teenager from taking off from the runway.
The issue sometimes termed "the yips" is not an uncommon problem among vaulters and although she says it is difficult to pinpoint why the issue suddenly surfaced, it was unquestionably "a really tough" period of her career.
"When you can't take off it is really hard because you can't compete," she says. "I always knew at some point I would be fine, but it was tough. "
In an effort to overcome the issues which dogged her during the first half of 2015 Eliza and Jeremy, adopted a back-to-basics approach. She stripped her vaulting right back to adopt a shortened run up and more importantly tried to adopt a more "fun" approach to vaulting.
Still struggling two weeks out from the World University Games in Gwangju, Eliza had her 'Eureka' moment in training just prior to the biennial student sporting festival.
"When I got to Korea and I started training at the same venue as my pole vault rivals, a real competitive streak came out in me," she says. "It was like a lightbulb had come on. I suddenly had a whole new mindset and I was absolutely fine from that point."
She went on to collect a confidence-boosting silver medal at the World University Games and ended 2015 on a high by taking the World Junior record courtesy a 4.64m clearance in Auckland.
The 2016 campaign has gone in her understated words "pretty well." She began the year setting three outdoor national records culminating with a stunning 4.80m clearance - and Oceania record - at the New Zealand Track & Field Championships in Dunedin.
She then made her debut on the global championship stage at the World Indoor Championships in Portland and placed a magnificent fifth to clear 4.70m.
"I had only qualified two weeks earlier and I was so excited to be there," she says. "I was a little bit star struck but I was happy to soak up the atmosphere of being on the international stage and took it as a good opportunity to learn and have a go. I only take good memories from that competition."
Yet sport like life never runs perfectly smoothly. In the countdown to Rio she picked up niggling hamstring and achilles injuries. A couple of weeks out from her Olympic debut she was forced to take a full week out from vaulting.
"I wasn't really sure how I was going to go in Rio," she admits.
Yet as history has taught us the down-to-earth and vivacious teenager went well in Rio. Very well. She kept her composure in the intense crucible of Olympic competition to win a magnificent and unexpected bronze by matching her lifetime best of 4.80m.
Her life has changed out of all recognition since her Olympic success. Overnight she has become one of New Zealand's most recognisable and marketable athletes.
So how does she feel about being Eliza McCartney Olympic bronze medallist?
"The funny thing is my coach and I have talked for the last couple of years about wanting to focus on Tokyo 2020 and the aim was to win a medal there. That has always been the plan. It is really funny to think I am an Olympic medallist, because it is beyond what I thought I could do in the time frame we had set."
With the support of her tight-knit and talented team coupled with her quietly determined character, Eliza has achieved so much so young and the sport of athletics has given her so much.
"Athletics has given me a pathway," she says. "I always wanted to go to uni and pursue an academic career then I got into sport and without realising it sport has taken over. It is funny how it has worked out. I only started pole vaulting because I wanted to try it, but if I am lucky I can carry on vaulting internationally for the next ten years."
