ice bath
© Graeme Robertson/The Guardian
‘Inside every human is an endurance athlete.’
I drop into an outdoor freezer full of water and ice, with no clothes on, in December. My body starts to buck, breath unable to leave my lungs. It feels as if I'm going into cardiac arrest.

I suspect that this one-to-one session with Tony Riddle, ultra-athlete and natural lifestyle coach, will be my ruin. When he greets me, too early in the morning, he is disconcertingly hale, with the focused gaze of a Viking approaching shore. Worse, he is wearing a pair of those amphibious foot-gloves. You know, the ones with individual toe sheaths that make you think a gorilla is walking towards you on its hands.

"Inside every human is an endurance athlete," is one of his remarks on meeting, which is a) too inspiring for a Tuesday morning, and b) not true. Beneath my feckless exterior is an even lazier core slob, only kept at bay with strategic food bribes and inconvenient council tax demands.

Riddle's "rewilding" philosophy is about reconnecting humans to natural behaviours - particularly ways of moving that modern lifestyles have estranged us from. We were not designed to sit for 10 hours a day, he explains. Electric lighting confuses our sleep cycles. Urban architecture encourages bad posture. The artificial repetitions of the gym encourage strain and uneven musculature. He winces when he sees my trainers, which is rich. Why are most shoes narrower at the front than the heel? he asks. A foot's natural shape is the opposite - toes are meant to spread, and grip the ground: we have more than 100 muscles down there. Thick-soled, cushioned running shoes cause these to atrophy, and deprive us of sensory feetback. I mean back feet. I mean feedback. Sorry, I've been sitting for a while.

I thought the session might involve gently foraging for nuts; actually, Riddle's thesis is that naturally developed bodies have incredible abilities. There's much focus on feet - "the basis of your superstructure". I stand on one leg, flailing, confirming my body has less balance than my bank account. Yet I find revelations, too. We practice the Wim Hof breathing technique, and I'm astonished to learn I can hold my breath - after exhaling - for a full minute.

Next, we move to straight-arm pullups, and I'm a little confused by these attempts to raise my body toward a metal bar, without bending at the elbow. Surely an anatomical impossibility, at best a physical riddle? Oh, my God, I think, arms shaking, his name is Toe Knee Riddle? Like a superhero alias. A few weeks ago, Riddle ran the length of the country barefoot, to raise money for charity, despite being born with underdeveloped lower limbs and spending years in braces. Needless to say, he pulls himself toward the bar using just his back muscles, until he is almost horizontal.

There are also simpler ideas for living naturally in the modern world: squatting at your office desk; "surfing" inside train carriages, which involves avoiding handrails and using micro-adjustments of your feet to balance; removing chairs from your home.

But the extreme ideas are fascinating. "Cold immersion is so under-rated," Riddle announces. I, however, don't think it's under-rated enough. He believes ice baths have benefits for cellular response, digestion and the immune system. I believe it will make my organs shut down. The disagreement is academic - I check my bag, realise I've forgotten my swimming trunks. Riddle looks at me in a way that seems to say: "That was a subconscious choice, to avoid the ice bath." He has a spare pair, he laughs, slapping me on the back.

And this is how I found myself climbing into a freezer of water, worrying about having a heart attack. "Breathe," Riddle compels me. Exhaling will calm my nervous system, he says. And it does. I stop shivering. I spend two minutes submerged in the ice, surprisingly calm. My body adapts, capable of more than I thought. When I step out, I feel superhuman.

You know what? I do recommend this. Rewilding chimes with me. It's not macho and it emphasises play. I would sooner climb a tree than up my reps in the gym. I like running the low walls in my neighbourhood, and prefer a dance around the kitchen to any fitness fad. A morning of getting back to nature has left me feeling vital and empowered. I wonder what six months of this could do.