McCartney told NZME she had considered retiring when faced with the uncertainties of where a revamped approach to the sport would lead to.
After enduring so much pain that she would often pull out of jumps, and then failing to qualify for Tokyo last year, she took an unprecedented three months off and her team had a major re-think.
"We stripped it back and asked is it worth continuing…what can actually be done with what I've got?" she said.
"We found it was less medical than we thought in the past…there have been chronic injuries and medical issues, I'm not the robust teenager anymore and we just didn't move fast enough to the changes.
"The main thing is there's no reason to think it is over…there are ways to do it differently which is exciting. I want to give it a real crack again.
"It's going to take time, you have to alter neural pathways, but I'm already able to do a lot more than I could last year."
Biomechanics expert Matt Dallow is the main new recruit to her team, with Jeremy McColl still her head pole vault mentor.
She has put a lot more emphasis on mental skills, partly to ensure she enjoys the new ride even if it doesn't go as planned.
And after years of being based solely at the Millennium Centre, McCartney has done her track work at Trusts Arena in Waitakere and gym work in Dallow's garage, although she will soon return to the North Shore venue as her vaulting work kicks back in.
When asked if she contemplated retirement, McCartney said: "Yes absolutely...I don't know if I can commit, what it is going to do to me.
"The new regime is a big path to go down. What convinced me most was there was no reason to think this was unsalvageable.
"That's what made me want to go again. Not giving it another go would have left me with a lot of regrets.
"I might not get back to being an Olympic medallist again, so it has to be enjoyable what I'm doing it, I have to have a reason for doing it now. We're working really hard on all aspects."
She loves to study and has used the break to increase her degree work which includes majoring in environmental science, but McCartney didn't want to rest on her bronze medal success.
"The way I didn't qualify for Tokyo (Olympics) would have been a very hard spot to depart on," she said.
"I've been offered a really good second way of doing things. It made sense to go again and throw everything at it, which is what we are doing.
"It's really been a really exciting change. This is all with the idea of getting to be at the Paris Olympics, and also being at my absolute best.
"This is the most confident I have been about getting to Paris and not just turning up, but being strong, fit and better than I've been."
McCartney said it had been very tough not picking up a pole vault and competing. She intends returning to the domestic competitions around December
