I've always had a rather unhealthy relationship with exercise. The more I've abused my body with life's little pleasures, the more I've tried to sweat it out with sporadic bursts of activity. My die was cast by my friend's late dad, who was a PE teacher at our school. Vic maintained a rigorous daily workout in his garden gym well into his 80s, but he also enjoyed sucking down his B&H cigarettes and his Burton ales. Although he regretted his lifelong love affair with the weed, he always said his aim was to "stay fit enough to enjoy my vices".

Which is why I'm on a Wildfitness course on the Isle of Wight. Because it's January, because I have a big birthday approaching and because I can't stand gyms.

I will never have anything approaching the constitution or discipline that old Vic had even in his 80s. I sense it is now or never for me and a healthier lifestyle. The fags have to go and the beer intake has to be reduced. But I know it isn't going to happen if I join a gym, as they've always left me feeling like a battery chicken on a treadmill.

I spend enough time cooped up indoors. What I need is a sustainable, free-range regime like Vic's with his battered old dumb bells and his weather-worn bench and the distressed punch bag hanging outside his back door. All I need is a kickstart.

Wildfitness appeared to fit the bill. Its website promised a fun training programme in the great outdoors coupled with a healthy diet and plenty of rest and recuperation that should leave me feeling re-energised and buzzing with "raw energy". The idea behind the holidays, dreamed up by Tara Wood in 2001, is to debunk outdated fitness methods, such as indoor exercise machines, and to re-engage with nature and the evolutionary principles that kept us lean and fit for thousands of years.

It taps into the movement towards a reconnection with nature that has gathered momentum over the past decade with activities such as foraging, camping, wild swimming and barefoot running. "Humans spent 200,000 years as hunter-gatherers adapting to life on the savannah. We were tall, strong, lean, fast, agile and fertile, yet we didn't need supplements or equipment to keep us fit and healthy. Nature provided everything we needed," according to Wildfitness's blurb.

And that is how I come to find myself doing bunny hops across the springy, sodden turf of the southwest downs within an hour of arriving on the Isle of Wight. "Really?" I think as the fitness instructor Paul Ranson suggests we move on to a series of animal exercises after completing a gentle run up to the top of the downs. Bunny hops followed by a great lolloping bear crawl, a leopard stalking close to the ground and then an angry bouncing chimpanzee? All around us open fields roll out to the sea, and all I want to do is race down them. Paul, sensing my unease, coaxes me through the sequence. I do it, of course, all five minutes of it, and all through gritted teeth – because it is bloody exhausting.

As I soon discover, these animal exercises are merely a playful warm-up to more strenuous activity. But they are engaging muscle groups that my body had long since forgotten it had, and I am already beginning to regret my scepticism at what I assumed to be primary school PE exercises.

The Wildfitness programme is new this year to the Isle of Wight – its home camp is in Kenya, and there are other bases in Crete and Spain – and is being run by two irrepressible sisters who grew up on the island, Ro and Netta Pakenham-Walsh. They have mapped out an adventure playground after a lifetime of discovery along the beaches and the downs of the island. They source most of the ingredients for the meals from their parents' garden, including the honey from their hives. And they have secured the most magnificent of bases for what might otherwise pass as a somewhat abstemious, luxe-free break – NorthCourt Manor, a Jacobean pile set in 15 acres of gardens in which many of the activities take place.

Over the next two days, in the shadow of its imposing walls, I attempt to remine some of the iron in my soul by completing circuits within its grounds and using its natural features as an outdoor gym. One of these sees me running up a bank on all fours, crawling across a lawn, hopping up a series of steps, jumping from a tree stump, hanging from a branch, throwing and running to retrieve a big rock, crawling under foliage, weaving through a bamboo plantation before running with a log. Not just one circuit, but to be repeated for 15 minutes.

Preceding this was a dawn 5km run-cum-walk along the chalky cliffs overlooking Freshwater Bay, tracing a route from the Needles and peaking at Tennyson's monument. I have to confess to retching at the halfway point to the monument – a regrettable discharge of the light brigade. But that only served to sharpen my appetite for a breakfast of home-grown raspberries and yogurt and poached pears with honey, followed by a couple of Aga-fried eggs.

There was also boxing training in the music room – we used to fight when we were hunter-gatherers of course – that included skipping (of sorts on my part), plank presses, squats and burpees before a session pounding the pads. If it sounds exhausting, it really was. The programme is graded for all levels of fitness, and Paul and Ro are exceptionally encouraging and enthusiastic coaches. Even though it often felt like murder at the time, and my body was crying out for mercy, as soon as I caught my breath and stopped sweating I felt more relaxed and re-energised than I had for years.

Obviously science and machines have helped extend our life expectancy somewhat beyond that of our hunter-gatherer ancestors – not to mention the noticeable lack of threat from sabre-toothed tigers pacing the savannahs of our isles. Even so, I left a little righteous and a lot inspired. So much so that when I returned home I raced for the wilds of Tooting Common for the first time in years. And I aim to keep on going. After maybe one final fag. Just kidding. I hope.

Essentials

The first UK Wildfitness three-day break is 12-15 April, with prices from £650 for a standard shared room (020 3286 4886; wildfitness.com). Andy Pietrasik travelled to the Isle of Wight with Wightlink (0871 376 1000; wightlink.co.uk) on its 40-minute Portsmouth-Fishbourne crossing, one of three routes. A super-saver fare (for a car and four people) costs from £47 for up to four nights away