Modern life has made us all so ill that we have been compelled to invent its polar opposite, “wellness”. It is not enough just to be well, there is an additional demand to be seen to be well. Wellness is complicated and needs time, money and access to special food, travel and social media. By chance in middle age, I discovered a cheaper, simpler and more enjoyable alternative: I took up boxing.

Boxing is cheap, unpretentious, sociable and has transformative powers. On the outside I am an ordinary 56-year-old woman, but on the inside, after six years’ boxing training, I have surpassed notions of “wellness”. I can also skip for England and throw a great jab.

Such was my enthusiasm for boxing that I felt compelled to keep a boxing diary, initially as a training aid. Inevitably, the diary got stuffed with notes and reflections detailing the camaraderie and the high and low dramas of the amateur boxing gym (there were many) and evolved into my book, The Boxing Diaries. I never meant to take up boxing or write a book, so how and why did I become smitten?

I found the ethos surprisingly non-macho and inclusive. Boxers were nice, self-effacing, thoughtful and dedicated

At 50, after an intense period of work and study, I knew that I was trapped in a gentle, terminal decline. Despite intermittent bouts of hill-walking and cycling, I found myself facing down middle-aged spread and knew it was time to fight back.

I was working as a school laboratory technician and not earning much, so pursuing fitness on the cheap was the main driver. I Googled “cheap gyms” in my local town near the Yorkshire Dales and found a youth club that appeared to have a gym open to the public. I went along one October night in 2013, expecting svelte people in Lycra, deep carpets and fancy coffee machines, but things turned out to be so much better: I had stumbled on a traditional boxing gym, running youth and adult boxing sessions for a mere £2.

Crucially, allcomers were welcome. On that first night the Scouse coach, whom I’ll call Gerard, asked: “How fit d’yer think yer are, love?”

“Not bad for my age,” I lied.

“‘I’ll ask yer again in six weeks,” came the swift reply. I joined the adult sessions for a punishing three-times-a-week regimen of hopping, skipping, jumping and punching the boxing bags and focus pads. Our small group of boxers was accompanied by Gerard’s faithful and excitable dog, who ran around the gym with us.

The first six weeks were very tough indeed. I discovered what it was like to really hurt after training, as I tried and failed to execute even the simplest manoeuvres. Nothing happened quickly, but over that short period I fell in love with the sport. I found that I was a serial grafter, determinedly in for the long haul, even though I had the grace of a sack of potatoes. I would never give up even when it was sensible to do so – a generous trait inherited from both sides of my family.

The training was tiring, but also exhilarating. I took the advice of a physiotherapist and did a couple of yoga and Pilates sessions per week (and still do) to build and maintain inner strength and flexibility. It was a joy to discover that in the gym no one cared how you looked, what clothes you wore, where you came from or even who you were, just as long as you gave it your all, were interested in boxing and were never late. It was that simple. I was hooked.

I found the ethos surprisingly non-macho and inclusive. Boxers were nice, self-effacing, thoughtful and dedicated. Occasionally macho men passed through our gym. We put up with their bluff and bluster but had heard it all before. They usually claimed that they had boxed for Britain and that some external force had cut short their burgeoning careers. Some expected to learn to box or skip from zero in eight weeks flat and were severely disappointed when they couldn’t. Radio 3 listeners and professors were generally the worst – they had a sense of entitlement and could never box, making them impossible opponents. They gave unwanted advice about how you could improve your jab. Most of them had no discipline whatsoever and melted away as we funnelled down to a determined core of regular grafters.

Appearances could be deceptive: there were largish men and women who could move like the wind round the ring; there were boxers who were willowy and light who could throw immensely powerful punches conjured out of nowhere; there were those with paunches who claimed never to have boxed, but had lightning-quick reactions; and some, like me, had reasonable fitness and power but moved like a slug. However, there were definite improvements. After six months I found I could skip quite well and do a few fancy rope tricks. After a year, I could throw a decent jab and right-hand punch.

We then came under the tutelage of a Welsh ex-army championship boxer and football referee, whom I’ll call Dai. Dai was our own local hero – an extremely reliable and disciplined coach who turned up week after week, year in, year out, without any remuneration, to put us through our paces. Dai’s speciality was the boxers’ brutal fitness circuit known as “the Board of Death” which, like a bitter medicine, we came to both love and hate. After 18 months of training I gained enough confidence to try some simple sparring in the boxing ring. I took the precaution of having some basic medical checks before getting in the ring, something I strongly advise, whether it is a club rule or not. I also bought my own good quality headgear and gum-shield.

It was an odd feeling getting into the ring for the first time, a bit like going to war, when someone starts shooting at you from over the parapet. I would not recommend it to anyone without a reasonable level of fitness, as the rates of energy burn defy description. There were few women in my club, so I was nearly always boxing men. However, as my fitness increased, I found I could tire them out, by throwing my strong jab and making them – not me – run around the ring.

Being punched in the head is a very bad idea and so I did everything possible to avoid it, learning some basic defences before attempting to spar. Mostly I didn’t do too well, but thoroughly enjoyed myself. Over the years, I got a couple of black eyes and broke a tooth, but my injuries were not serious and few and far between.

Success for me was defined as defending myself over three two-minute rounds and getting a few sweet shots through. Boxing is never about uncontrolled aggression or anger, only about outwitting your opponent – and therein lay the satisfaction. I think that certain friends and family members found this hard to grasp, as they could only visualise boxing as a 12-round professional bout with Joe Frazier. Consequently, they saw my lurch towards the sport as odd and slightly dangerous. My brother-in-law blamed it on a mid-life crisis that would surely pass.

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Others questioned how I managed to shoehorn two or three sessions of training into a busy week. It doesn’t sound like much, but with a reasonably long commute and antisocial working hours, a degree of discipline was required. Even with my small commitment, getting enough rest was important and sometimes problematic. I am certain that this would have been virtually impossible had I been a parent or carer. Along the way, I came across too many who longed for the opportunity to take up regular sport, but were too exhausted, lacking in time, money or support to do so: this has to change.

Boxing is described by many as both a science and an art. When executed well, it feels like a dance with many challenging technical aspects. It is also very sociable. Participating means joining a global brotherhood or sisterhood melded by years of discipline. At the amateur, non-competitive level it is relatively safe, if properly supervised by trained coaches. It also feels like a natural activity – something missing from life that has been restored. Evolutionary biology bears this out, as those with proportionately shorter legs (like me) are supposedly adapted for fighting as they have a low centre of gravity.

I am still boxing at 56 and it is a challenge I am not ready to give up. I recently crashed and wrote off my car. Thankfully no one was seriously injured, but I nursed badly bruised ribs for about a month. The very worst thing was missing 10 training sessions. But it was all that core strength that saved me from being properly broken.

The Boxing Diaries (£9.99) by Marion Dunn is published by Saraband on 23 January. Order it from guardianbookshop.com for £8.79