In my experience, there is a shortcut to most things in life. Exams can be crammed for, interviews bluffed and deadlines renegotiated. I even blagged my driving licence on my third attempt, by convincing the instructor he would rather watch me perform a three-point turn than a parallel park. Can the same be said about marathon running? Might there be an easy way to haul oneself through 26.2 miles without enduring the months of hardship – blisters, sore muscles, early morning runs and exhaustion?

The short answer is: not quite. Preparing for an endurance event such as the London Marathon, which I am running on Sunday, does take a certain level of dedication and determination, the two key elements I felt I was lacking. Oh, and fitness. But after a little frantic digging I discovered some corners could be cut: conventional marathon training advice generally advocates 16 to 22 weeks of heavy mileage, running five or six times a week, and loading up on carbohydrates to pump your muscles full of extra energy to expend during the race itself. I have boldly flaunted this method, repeatedly tried-and-tested by millions of marathon runners. Instead, I have been focusing on short, high-intensity workouts to build core and upper-body strength, combined with a long run each weekend.

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Marathons are bad for you

I want to shirk the running through general laziness, but the fitness expert I find to back this plan has a more sensible reason for cutting back. "Running for an hour every day puts your body under so much stress that it begins to break down," says Mike Weeks. He should know: though his interest in fitness was kicked off by a passion for rock-climbing, in 2006 he and his partner, Bean Sopwith, undertook the challenge of dragging Jack Osbourne around the Marathon des Sables, a seven-day, seven-marathon race across the Sahara. Weeks ran three marathons a week in training and saw his connective tissue and muscle density drop away.

"You'd have to put a gun to my head to make me run for more than a couple of hours," he says. "So many people think running the marathon will make them healthy, and it's quite the opposite. Many people leave it to the last minute and then think: 'Shit. I've got to start cramming in.' Their body is just annihilated in the training."

Weeks has a good track record in rehabilitating worn out Ironmen. "They want us to train them harder but we get most of them to stop doing any exercise apart from strength training for 10 or 12 weeks. Usually most of them are so weak it's unbelievable to think they are athletes in their prime."

The training plan

I first hit upon the idea of running the marathon in mid-January. I head out for a 12-mile run, out of shape and wearing old trainers, and come back with my first running injury. A large swollen pillow of fluid has ballooned under my left knee, and I can barely straighten my leg, never mind continue with the running programme I had found on the internet, which would have me running six days a week. Weeks takes one look at me and decides I should spend my first weekend of training lying in bed eating jelly – the secret weapon of all injury-free athletes, apparently.

Over the next two weeks I get started on some light exercise – a few three-mile jogs, some interspersed with a few minutes of running at an increased tempo (known in the business as fartleks), and some gruelling sessions with Weeks of lunges, sit-ups and press-ups (girl press-ups, with my knees on the floor), some weight-lifting and lots of bobbing around on a Swiss ball. After two weeks I am ready to start running slightly longer distances, and kick off with seven miles. Before the run, I do a session of circuits, the idea being to cram some high-intensity training into 20 minutes or half an hour, thus avoiding too many long and dull runs.

A further two weeks and countless bowls of jelly later, I start training proper: three days on, followed by a rest day. The sessions are between 30 and 50 minutes each, and involve such joys as going for walks with a 5lb dumb-bell in each hand, doing lifts and raises as I go and getting lots of amused looks from passers-by. I also get to play with the TRX suspension kit, innocent-looking nylon straps that we attach to a tree in the park. Doing push- and pull- and sit-up-style exercises while gripping the straps forces muscles you don't know you have to spring into action to maintain your balance. Still a weakling, I pull something in my side, and even eating hurts a bit for the following week.

Diet and equipment

Finding it painful to eat throws up new challenges, as Weeks has decreed I eat every two hours, following a strict diet of 40 per cent protein, 30 per cent fat and 30 per cent carbohydrate, determined by a lengthy questionnaire. His suggested snacks include a rye cracker smeared with a thick layer of butter followed by an even thicker layer of pâté. If I want to drink wine, I should eat some cheese beforehand.

Smoothies (health drinks, surely?) he labels as: "Junk. Very well-marketed bottles of insulin and cortisol-raising sugar." Apparently my hormonal system is in tatters and my adrenals fatigued, which means that where most people rely on adrenaline once they begin to tire (ie, after running 10 miles or so), I have few extra resources to fall back on. So he directs me to a company called Solgar, and demands I take a cocktail of their herbal supplements and vitamins. I have never taken a vitamin before and am cynical when it comes to loading up on capsules and pills instead of just eating well, but three or four weeks after taking an omega-3 fatty acids supplement, my hips, knees and neck have stopped clicking every time I move.

Equipment-wise, Weeks directs me to Profeet, where I spend a pretty tedious hour running and watching videos of myself running, and looking at high-tech graphics of my "bilateral anterior distal knee pain". Profeet makes a special pair of insoles moulded to my feet to even out the pressure.

The traditional approach

I turn to Andy Dixon, editor of the marathon geek's bible Runner's World magazine to compare notes. Dixon, 35, joined the magazine last year, and like me is running his first marathon on Sunday. He says there is no failsafe way to train. "Listen to your body," he advises. "If you've got feet like lead, there's no point trying to force it." He does advise taking on a lot of carbohydrates in the three or four days leading up to the marathon. "The lifestyle changes of training for the marathon," he says, "will counteract any damage you do during the race itself."

The final furlong

Ten weeks after signing up to Weeks' training schedule, certain benefits are quite startling. I sleep so soundly that even if I only get four or five hours, I wake feeling refreshed. Eating regularly and keeping my blood sugar steady has done wonders for my concentration and work efficiency. Previous training for half marathons has given me tired and sore legs; this time they haven't felt worn out at all. The one sticking point, which I challenge him on repeatedly, is Weeks' insistence I pump iron and pig out on protein: I fear I will end up looking like a champion shot-putter. Whingeing gets me nowhere, though, as his only concern is getting me marathon-fit in the least painful way possible. To be honest, being able to do chin-ups is kind of cool.

Two weeks before the event I do my final long training session: 35 minutes of hard circuits and an 18-mile run. Weeks estimates, in my opinion somewhat generously, that the circuits are the equivalent of an 8-mile run – at his pace, maybe. I do not think I can move one more inch after the 18 miles and collapse on my doorstep for a good 10 minutes. Still, I ran it in two hours and 45 minutes. The London Marathon's director, David Bedford, laughs when I explain my training plan to him. "I assume you don't think you're going to be able to run the whole way?" he says, rather uncharitably. He revises this opinion when he hears I have run 18 miles. "In truth, [weight training] is better than doing nothing, but if you'd spent that time running you would be in better shape than you are." I disagree. This Sunday, we'll find out who's right.

Sophie Morris is running the marathon for VSO. You can visit her sponsorship page at www.justgiving.com/sophierunslondon and check up on how she did on her Ethics Girl blog

Marathon training the easy way

Mike Weeks is not against running, provided you are in good shape and keep it to 30- or 40-minute runs, a few times a week. Here are his top training tips:

1. Check that your body is ready to undertake some serious training. Is your breathing OK? Are you drinking enough water? Are you sleeping well? Make sure your diet suits you.

2. Sign yourself up for circuits a couple of times a week. If you lack motivation, see if your gym offers circuit classes.

3. Kettle bell workouts. These funny-looking weights are one of the secrets of Eastern Bloc strongmen. Studies show regular lifting can improve the performance of running, sprinting and pull-ups.

4. Find a friend and do some full-body, functional sports, such as martial arts or climbing.

5. Work up a sweat doing 25-minute fartlek runs.

6. Yoga. Fringe benefits include adding years to your life and feeling happy all day.

7. Buy yourself a bike and go mountain biking, or for a gentler countryside outing.

8. If you live in a city, escape it with a long hike.

Contact Mike Weeks at 020-7341 0825, www.thebodyalchemist.com

Getting ready for race day

David Bedford, 58, is the race director of the London Marathon and a former 10,000m world record holder and Olympiad. He ran in the first London Marathon in 1981 after a heavy night of drinking, a curry in the early hours and just an hour of sleep. He doesn't recommend this approach, saying "the second half of the marathon was probably the worst experience of my life". Here are his tips for beginners.

"It is too late now to do any additions to your training. It is very much more about managing what happens on the day. Keep your alcohol content low and try to get extra sleep, because on Saturday night you will be nervous and excited and will have difficulty sleeping.

"The key is not to start too fast. Be realistic about what time you think you can do for the full marathon and go through to halfway at a slower pace, to make sure you get there feeling good about the experience. Then you can speed up if you've got it. If not, you've got more chance of maintaining your speed and getting to the finish line."