It's more than ten years since I drove to Mooroopna in country Victoria and artlessly pummelled a blonde girl called Storm Brainwood. And even then I wasn't young. I was in fact three years older than my boxing age, which at the time was listed as 30. One of the officials had told me to, 'turn that second three into a zero, darl,' when I filled out the paper work, which bought me a little extra time. When I eventually stopped competing most people knew I was closer to 40 than 30. But they turned a blind eye.

My husband Peter remembers standing in the crowd that night; a sea of flannel shirts, beanies and stonewash stretch jeans and hearing a man say to his mate as we entered the ring, 'Yeah, I reckon I'd root either of 'em.'

These days I'd be flattered to hear such an objectification since I'm now approaching that age when women become invisible.

From that first foray into the ring in Mooroopna I believed my time in competitive boxing would be short and hopefully sweet. Instead it has been like a long-term relationship with another human being, shifting and adjusting as the years pass, swinging from obsession to revulsion and back depending on the circumstances. I've accepted now that I am pretty much shackled to the sport for life.

By the time I went on my inaugural boxing pilgrimage to New York in 2007 I thought I was over the hill well and truly as far as fighting was concerned. In the boxing world anyone nudging 30 is almost ready for the scrap heap. People like to say it's a young man's sport. There are some notable exceptions like Bernard 'The Executioner' Hopkins, who at 43 is still competitive at the elite professional level. And Muhammad Ali's one-time nemesis George Foreman returned to a weak heavyweight division in the 1980s at the age of 40 and won the world championship at 45. His opponents were drawn from the sport's massive pool of journeymen plodders, but still, he kept it up respectably until the brink of his 50th birthday.

Usually, though, boxing and aging don't marry well. But if there is one group in society more anxious about aging than boxers, it is women. So what happens if you fall into both camps? Do you worry more about frown lines or reflexes? I now find myself in the unique position of contemplating such questions because I was reborn as a competitive boxer in America last year when I was 45 years old. I fought in the masters division of USA Boxing, an over 35-age category that isn't available here. Amateur boxing has an international cut-off age of 34 but in the US the masters are a growing force.

In May last year I registered with Gleason Gym in Brooklyn and had five fights across the country in as many weeks and came home undefeated – the National Golden Gloves champion, the Georgia Games champion and the Ringside World champion. I seemed to have hit some kind of sweet spot in which experience and fitness were perfectly synchronised. I entered the ring each time with a serenity I'd never known before.

And to my surprise there were enough middle-aged women in the US willing to take their chances with me, which was astounding considering that even when I was 'young' in Australia I couldn't find enough opponents. And, more incredibly, many of these women were competing for the first time.

It's impossible to be dismissive about such a step. These women were defying expectations on so many fronts, in and out of the sport, it was startling. It takes a rare kind of chutzpah to step through those ropes for the first time and to do it at an age when people expect you to be fanning your hot flushes takes extra nerve and resolve.

Older athletes are nothing new. But while they've been a common enough sight in marathons, cycling and other track and field events for many years now, a boxing ring has generally been considered among the worst possible places on earth in which to grow old. Being entrenched in the sport, I always hear stories of former greats succumbing to the march of time. Age is often invoked in boxing as the sole cause of someone's downfall. 'How old is he now?' You hear it all the time. So really ageing as a woman boxer should be a double blow for me. But somehow it has been the opposite. My skills are improving with time and now I have extra time, unlimited time, actually, because there is no cut off age in the masters. I feel younger than my non-boxing cohort, untroubled that male eyes skim past me, enriched by the new and uncomplicated friendships I have with young men in the gym and enjoying the authority that comes with a few wrinkles.

It was on a Gleason's show where I first saw women masters in action and it was there that it dawned on me. If they can do it, so can I. And I eventually set off on my journey nearly two years ago.

After a while, it started to look like boxing was an elixir of youth, an anti-aging formula more powerful than human growth hormones and injectable collagen. I met female veterans who were retired but still active in the gym in their late 40s and looking incredible. Women like Bonnie 'The Cobra' Canino, still sparring with unlimited reserves of energy and sledge-hammer punching power. I met an active fighter and super human creature called Alicia 'Slick' Ashley, a world champion bantamweight in her 40s who made fighting look like a skip in the park and turned women half her age into stumbling fools. I met the Guinness Book of World Record listed oldest world champion female fighter Terri 'The Boss' Moss who at 43 had the complexion of a 30-year-old and the metabolism of a 12-year-old boy. Novice or veteran, they were remarkable women. But the novices perhaps more so. What an extraordinary way to play out the narrative of female ageing in this society. The standard options are to sink into a torpor over what you have lost, lamenting some illusory power that came with your attractiveness to men. Or else you can reclaim that lost allure with plastic surgery and turn yourself into a Cougar. Or just vanish. Become a soccer mom and retreat to the sidelines. What defiance, then, to transgress the conventions of both gender and age and remake yourself as a warrior, demanding attention and standing alone. Here was a group of women heading in a new direction entirely, finding means of exerting power and expressing themselves, that seemed to be more sustaining than whatever might be gained from the ability to make men to drool. In the era of the middle aged sexual predator, the 'glam-ma' here now were some genuinely courageous individuals who, as women, didn't want to go over the same old ground, didn't want to bat eyelash extensions at busboys or buy enhanced cleavage. My admiration for them was high.

Boxing can be painful. It's tough getting hit in the face, having a bleeding nose, black eyes, sore jaws, a cricked neck. And there's much more pain in the early days, when your defensive skills are undeveloped, when lessons learned are sharp and cruel. It's hard when you're young but maybe older women are tougher. And in boxing people often discover that they are more resilient than they gave themselves credit for. You take a step closer to yourself, your fears and weaknesses. Could it be that these women liked what they saw inside and worried less about what they saw on the outside? I'd like to think so.

Despite the brutality of learning to box, I would guess some non-boxing women are willing to suffer much more pain in order to defy, merely the appearance of age. From watching episodes of Extreme Makeover I've concluded that they endure many more invasive and horrific forms of pain than even a top line boxer would consider tolerable.

The most popular cosmetic surgery procedures are botox injections and liposuction – the reconfiguring of body fat, sending plumpness to the face and taking it away from everywhere else.

I could be wrong but I suspect also that those who would willingly submit to being hacked into with a scalpel might also recoil from the violence of boxing. But how can some of the cosmetic surgical procedures not be considered violent? Removing flesh, inserting foreign bodies, risking infection, bleeding and possible death. I think at the moment I would rather endure the less invasive pain I have come to know, keep the frown lines and crows feet and carry on fighting.

Staying fit enough to box has ensured that at least my body, if not my face, is defying time. I'm actually in better shape than I was in my 20s. The best shape of my life, in fact. No liposuction for me. As well as boxing, I run three or four times a week and lift weights. I have a body mass index of 23.3 and a resting heart rate of 52 and am in the 95th percentile of fitness for my age. I know this because I needed to get medical clearance to fight.

That first female masters bout I saw in New York was between 52-year-old Maureen Reineger and 46-year-old Leila Ferioli.

It was Maureen's second fight. Her first had been against a Detroit woman, another debutante, who had been a year older. I'm pretty certain that a 53-year-old female novice boxer is not something the world would have contemplated a decade ago. Even today it seems somewhat unbelievable.

What will the medical profession make of this trend I wonder? The official medical objection to boxing has usually been a moral since they have little quantitative medical research on the sport itself on which to base their opposition. I often wonder how their likely objections will sit against the increasing number of procedures performed on women of a certain age; tummy tuck, lipo, brow lift, breast implant. Name your poison ladies. Maybe it's just HRT and some anti-depressants.

Personally I'll vote for the moral purity of pugilism over the snake-oil salesmanship of makeovers masquerading as medicine. There is no deception in boxing, at the very least. What you see is what you get.

Maureen Reineger, by day a manager for New York City transit authority, had a theory. She said that in older women, although oestrogen levels declined, it gave testosterone a chance to come bursting to the fore, which is just what you need in a boxing ring. As a theory, it might not be medically sound, but as a glass half-full philosophy, it was good enough for me.

When I watched Maureen fight her three rounds against Leila in Brooklyn in the fall of 2008, my immediate thought was that these were typical novices, fighting mostly on adrenalin and fitness. Their skills were rudimentary. Maureen was a southpaw, which also made the whole thing look slightly more messy than it otherwise would have. I'm not being disparaging here. My own debut in Shepparton was like a spaghetti western.

I remarked at the time to my friend that the women 'looked kind of old' before they put on their head guards and stepped into the ring. I'd seen both women training at Gleason's but hadn't paid much attention to them since the place was swarming with younger and more talented female boxers.

A few days after the fight I spoke to Maureen. She struck me as an intense, somewhat awkward person and it didn't surprise me to hear that she lived in Long Island alone. Fair haired and tall, she wore tight black training gear. She was being trained by two Puerto Rican larrikins Melissa Hernandez and Belinda Laracuente both elite professional fighters in their 20s, young enough to be her daughters. I watched her hit the bag with more raw energy than refined skill, sometimes both hands coming out at once in her drive to work it. She looked slightly uncomfortable but nonetheless determined.

Later we went to a café nearby to talk about boxing.

Maureen had a soft voice that was hard to hear over the swelling dinner-time clatter. There seemed something a little brittle about her. She was 2-0 as a boxer but she had an almost prim manner.

'I started out with a boxing workout,' she said. 'But I always wanted to spar and I always wanted to fight. I never wanted to do the work out just to get in great shape.'

'I like the idea of the combat aspects of it and the contact and just the power of being in the ring and just being in there by yourself. It's like your totally in control of yourself, making decisions,' she said.

I asked her what she thought about starting so late. She explained that when she was younger there were no women boxing.

'But I don't let things like age stop me. I've been in excellent health and I've always been active. I don't have a lot of wear on my body. I guess if I had been active in sports as a teenager or in college or on a soccer team I probably would have more wear and tear. And I don't have a husband and kids so it wasn't like a lot of energy was going towards that. I was married but it didn't work out. That was a long time ago when I got divorced.'

Having boxed now for nearly 15 years, I was reminded by Maureen of those early feelings, that first blush of love for the sweet science, some aspects of which I now take for granted. I remembered why I had been so infatuated in those early years.

'Boxing has given me a lot of confidence and a lot of composure,' she said. 'It gives you this unique feeling that you can get through all sorts of difficulties and not just physical but mental. It teaches you to focus, I could go on and on. People at work have mentioned it. Just with my confidence and forthrightness. I walk the walk. I'm not afraid to speak my mind, although I'm diplomatic. I was always like that but I was reticent about voicing my opinion on something. I don't have a problem giving an opinion or saying something now and if somebody is offended by it? Now it's like whatever, this is how I am.'

Maybe this was an ideal time in a woman's life to be boxing after all. A time when she wants some authentic existential answers. This is how I am. Don't we all want to be able to say that, and also to know it at some deep level?

I asked Maureen what lay ahead.

'I want to continue to fight,' she said, 'I love training and I want to push myself more and more. I want to keep winning, it's always great to have a win.'

Boxing has never ceased to be full of surprises for me. The people who gravitate towards its hot core, inside the ropes, under those lights, willing to put, as Terri Moss said, 'not just your ass but your ego on the line'. They are never how you expect them to be outside the ring – the strong are often not particularly muscular, the ferocious are often shy and the tough can appear fragile (think of Mike Tyson's squeaky, lisping voice).

But people are trying to make something real of themselves by boxing. They want to know something true and pure about who they are. They are willing to walk around with their skin off to some degree. You can see their hearts beating. They don't want to paper over the cracks with illusion and fakery.

There are plenty of grey-haired men in boxing gyms and I suspect I will be part of a new wave of elderly females also donning gloves and stiffly whacking that heavy bag, shuffling around, talking about all the great fights, exaggerating my triumphs and glossing over my defeats. And maybe yes, I will look my age. But I sure as hell won't feel it.