"I can't do it," I yell, quivering, across the massive gap that lies between me (standing on a platform some 50ft up a tree) and the twitching biceps of the French ski team's strength and conditioning coach, Pete McKnight. He yells something positive back, as he has done for the past few days, each time I've said "can't" or "won't". He's relentlessly encouraging, extremely knowledgeable and charming. What's more, for a precious six days, non-athletes such as me can get the benefit of his expertise on Adventures in the Alps' fitness week, which, he says, is "designed to give people a taster of different types of training in a beautiful environment, empowering them to take control of their own fitness programmes when they get home".
Variety, beauty and empowerment? Sounds perfect. So here I am, in the lake and mountains of Annecy in France. Perhaps better known for winter-sports resorts such as La Clusaz, Le Grand Bornand and Manigod, it's the ideal spring or summer base for active travellers – a 45-minute drive from Geneva and with some of the most majestic and varied scenery I've ever seen.
This afternoon's challenge is more mental than physical (granted, scrambling up netting and hauling up rope-ladders isn't quite as relaxing as sunbathing, but if you want that, the lake has several grass beaches). I'm attempting the Forest Rope Course at Parcours Adventure in Taillores (think Go-Ape on steroids) and still shivering at the thought of this leap, the "Tarzan" zip wire.
"Just jump!" McKnight's voice booms through the trees and, not wishing to disappoint, I appear, grinning, a few seconds later on the other side. I don't have time to congratulate myself – there's a longer zip-wire still to come – but after two hours of balancing and jumping (at all times safely harnessed in), I feel refreshed, as if emerging from a long and lovely meditation.
It's not the first time this week either. The same thing happened this morning when McKnight dragged a portable squat rack out of his van and set it up outside our beautiful chalet, Domaine du Paron, so I could practise my Olympic lifts with a tip-top coach while looking out over Lake Annecy from 1,200m. And yesterday, during a group run through the forest. And the day before, when hill sprints left me struggling for breath. It even happened on our first day's gentle cycle from Doussard to Annecy town.
I should be exhausted by now, but the Alpine air, astounding views and our thrice-daily locally sourced meals stave off fatigue. What little muscle soreness does arise is swiftly pummelled away by a visiting, local masseuse.
Fitness Week doesn't include anything higher than the Cliffhanger Course at Parc Adventure. However, Adventures in the Alps founder, Pip Watkins, will happily organise paragliding, white-water rafting or the chance to try your hand at Via Ferrata, a series of climbing routes, first developed by the Italian army in the First World War to aid the transit of troops across the Dolomites.
With such a huge amount going on I'm slightly surprised that the streets of Annecy aren't awash with buffed-up tourists. People are cottoning on though: Lake Annecy Ski Resorts claims an increase in spring and summer visitors over the past three years. Since Watkins established Adventures in the Alps three years ago, it was shifted from athletes' training camps to offering pilates, yoga and walking weeks as well as the tougher trail runs and Alpine cycling. With her convivial, can-do attitude, she's forever pushing the philosophy that exercise can and should be fun.
Even on McKnight's Fitness Week, there's still an opt-in, opt-out attitude. So, if you fancy the hot tub instead of hill sprints, nobody will judge you (not too much, anyway). The weather helps things along a lot – last year in more than 16 weeks of training camps not one full day was lost to rain – so activities can include anything from open-water swimming to canyoning, kayaking, mountain biking and running on a cinder track at Faverge. Perhaps "just jump" should be the company motto.
Geneva is served by easyJet (0843 104 5000; easyJet.com) from Bristol, Edinburgh, Gatwick, Luton and Manchester; British Airways (0844 493 0787; ba.com) from Heathrow; Jet2 (0871 226 1737; jet2.com) from Leeds-Bradford; and Swiss (0845 601 0956; swiss.com) from London City and Heathrow.
The next "Fitness and Adventure Week", is from 7-14 September (020-7193 7660; adventuresinthealps.com), for £1,000pp including six nights' full-board with personal training, spa use and local transport, but not flights.