It occurred to me, as I battled a stitch through a pine forest while a man with a body like a chest of drawers urged me to “Compete or complete!”, that some people’s idea of a holiday simply beggars belief.

Even more bewilderingly, I thought through variable levels of consciousness, not only had the other “guests” on this arduous slog cheerfully volunteered to suffer this, they’d actually asked for it to be made harder. That’s right: when some people book a holiday, their biggest concern is whether it’s going to hurt enough.

In:spa was set up in 2003 to offer week-long health holidays to the make-me-perfect generation, serving up an improving regime of yoga, running, hiking, kayaking and virtuous dining. Then, last year, a few regular clients offered feedback. The holidays were very nice, but they wished they could be just that little bit more sapping. Shattering, even.

The Intense Week was born: longer runs, harder circuits, more shouting, flatter tums and firmer buns. There was no option but to sign up, fly out to the Ibizan interior and find out - just how hard can a holiday be?

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Our location was Es Cucons, a casa rural half an hour’s drive northwest of all the usual action, with pine-covered hills spilling a sense-perking aroma into the Corona valley. The perfect location to set about achieving a heightened sense of wellbeing.

My personal fitness itinerary was waiting in my room, in response to a pre-departure questionnaire that ascertained how shop-soiled my physique was and what my aspirations for the week were. I must have ticked the wrong box, because my first appointment was a pre-dawn run.

My watch glowed angrily that it was 7am. Seventeen expectant bodies and minds had assembled for a four-mile circuit of the valley, visible to each other only via neon flashes on expensive running kit. I felt a tad underdressed in my tennis trainers.

“Let’s go,” said James, a 6ft 6in leviathan with an oak jaw. “But I haven’t been to Starbucks yet,” I replied, trying to inject humour into a seriously unfunny situation. “Hard yard, less lard,” said John, an equally impressive human specimen. Both were personal trainers to persons whose names they were not allowed to divulge, but this week they were ours, and we were theirs to do with as they saw fit. And they certainly did see fit.

I took off like a 10-year-old at sports day. Three-quarters of the way round (the morning sun was lasering a hole through the back of my head by now), I wished I hadn’t. I remembered Kathryn, our host, saying at our briefing that this week was about “going at your own pace” and keeping your personal goal in mind. I told the marathon runner I’d foolishly tried to keep up with to go right ahead. She declined, saying she was taking it easy, as she’d just had a baby.

At base camp, we were all ready to drown in one of the promised smoothies when Doug, the third man mountain in the training team, called us back for a group “stretch-off”. A few of us were feeling stretched enough, but we had to be introduced to our muscles’ real names and told how to treat them so they didn’t turn against us. My rectus femoris and gastronemius were already livid, and it wasn’t even 8am on the first day. But they were about to get a boost – the first breakfast.

Nutrition is a big part of these trips: balancing your blood sugar, taking in antioxidants, getting rid of the 4pm slump, that kind of thing. My presumption that the food would be scarce and leafy was naive: it was salmon, scrambled eggs, linseeds, sunflower seeds, pumpkin seeds, more seeds, pumpernickel, pineapple, porridge, kiwi, melon, muesli and, of course, the smoothies. After some lemon and ginger tea, to wash all those seeds out of our teeth, we were ready for coffee.

Except that there isn’t any. No coffee, no tea, no salt, no sugar, no alcohol - five little things we struggle to contemplate life without. The abstention we’d signed up for suddenly dawned on us. Discussions broke out about who’d crack first, and who had secret stashes. I kept shtoom about the Monster Munch in my bag.

That afternoon James and John “beasted” us around a circuit they called the Axis of Evil. “If you don’t use it, you lose it ... Strengthen and lengthen,” they bellowed – but this was tongue-in-cheek sergeant-major stuff, and we were allowed to go at a pace that didn’t make us sick. After all, we were on holiday.

I wasn’t prepared for my first massage. Maria, Amazonian in stature and with goalkeeper’s hands, performed deep cellular cleansing. Little went untouched; not even my eyebrows escaped her rigorous attention. When she pulled my toes, they sounded like corks popping. I was left feeling like Morph must’ve felt after his first animation. Subsequent massages were less severe and, at one point, induced near-coma. When you’ve had peace rubbed into your bones, you just want to keep it there, so I tried some meditation under a muslin-roofed gazebo.

Yoga came later, on a plateau overlooking a valley of almond groves – exercise with a view. I’d say, on imbalance, that standing on one leg, praying, in the wind, isn’t for tall, skinny blokes. I was like a big plant with an inadequate root system. Yoga is hard work, and girls are better at it than boys – their hip flexors actually flex. As the week wore on, though, it began to take me to places I’d never been, physically, and it felt good.

In fact, apart from having our wineglasses filled with water each evening, a lot of this trip felt good. We ate proper food, we did real, meaningful exercise, and the group dynamic made it virtually unthinkable to abandon our quest of bringing together body, mind and spirit. By the back end of most holidays, I’m imploring myself to cut down on the booze and food, but, as this experience drew to a close, I felt the strange luxury of entertaining the opposite viewpoint. I’d earned a few vices – but craved even more virtue. It felt, we all agreed, as if the incentive to stay in touch with our bodies’ needs had been irrevocably implanted. And the Monster Munch stayed in the bag.

Simon Spilsbury travelled as a guest of In:spa (0845 458 0723, www.inspa.co.uk), which has two “intense” retreats in Ibiza next year (April 23–30 and October 9–16). Prices start at £2,295pp, which includes seven nights’ accommodation, transfers, all meals and drinks, physical activities, a one-on-one nutrition consultation, a personal training session, yoga classes and three deep-tissue massages. Flights are extra: airlines serving Ibiza include British Airways (0870 850 9850, www.ba.com) and EasyJet (www.easyjet.com). In:spa also offers intense retreats in Seville and Agadir, as well as classic and yoga retreats in Marrakesh, Andalusia, Ibiza and Tuscany

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