The fitness world is full of inspiring stuff; people, stories, ideas. But never has something moved me quite as much as the This Girl Can campaign which launched this week, which shows real women exercising - while kicking ass and having a ball in the process.

There's no alienating 'Go hard or go home' type messaging, with perfect-looking bodies parading around in designer Lycra. And this isn't about telling women they 'should' be working out, in order to lose weight, or whatever.

This is about women who exercise for themselves, for the love of it, and for the countless rewards they get from it - and to hell with worrying about how wobbly their thighs are when they jog, or whether they're always the slow one at the back of the aerobics class getting the steps wrong, or that they'll probably never do more than 20 lengths in the pool.

Because exercise really is for everybody. Never train for a triathlon? Doesn't matter. Not bothered about personal bests? Who cares. Don't have an 'ideal' swimsuit body? So what - you can still get your sweat on and get those endorphins pumping - just like the women in the campaign are doing.

There's Victoria, a 29-year-old A&E nurse, whose spin classes give her just the boost she needs to cope with a stressful night shift; 31-year-old Kelly, who pops on a workout DVD or some music at home, so that being a single mum doesn't have to stop her from exercising, and Grace, who loves nothing more than getting outdoors on her bike - it's exhilarating, relaxing, and no gym membership fees required - the fact she's (in her own words!) a bit slow, really does not matter.

"We did a lot of research beforehand, and while we developed the campaign," says Jennie Price, CEO of Sport England who are leading This Girl Can. "We've known for a long time that the gender gap between men and women in the UK is very stubborn in sports participation - it's around two million. But what I'm very cheered by is that 75% of women want to be more active, which we discovered through our research."

Of course, time limitations, childcare and cost are all factors in stopping us exercising as much as we'd perhaps like to; but Sport England found that the biggest barrier women admitted to is fear of judgement.

"If you're a bit uncomfortable with your body - and lots of women are, even if they don't really need to be - you have this dialogue in your head, that says, 'I'm not really good enough for this, I'm not fit enough to be in that gym, I can't put those Lycra trousers on because my thighs are enormous' - whether they are or not is irrelevant; you think they are, so you don't go.

"One of the things we're trying to get across in this campaign is that if you feel like that, you're not alone - but there is a way to think about exercise and fitness and sport where that doesn't get in the way. It's absolutely fine to do this, whatever you look like and however you feel!"

The campaign's currently due to run until March, with TV and cinema ads and posters; the first TV ad aired on ITV on Monday evening, during Coronation Street.

It's stirring stuff; partly due to the upbeat music, but mostly because the ads really capture what they set out to capture, that every woman - yes even you who gets palpitations at the thought of wearing a swimsuit, or you who thought you were scarred for life after coming last in every race at school - can enjoy exercise.

A year in the making, the women featured were street-cast from leisure centres, Zumba classes and parks across the country. The team spoke to 100 ladies to find the ones with exactly the right stories and who embodied the campaign's message.

And Price is keen to point out that this message is entirely based on research, from their survey results and feedback from focus groups. "It wouldn't be quite as strong if we'd just dreamt it up," she notes.

The timing, of course, is important - we all know there's an obesity epidemic going on, many of us are failing to meet the recommended minimum guidelines for physical activity, and lifestyle related diseases like Type 2 diabetes are creeping up and up, threatening our health and draining the NHS.

But, this campaign is not about scaremongering, or guilt-tripping.

"We're trying really hard not to preach. I think we all know we should be eating healthily and need to be a healthy weight and that sort of thing, but sports as a healthy route is one that doesn't always feel open to us," says Price.

"And I think there is also something about empowering women to be what they are and who they are, and that's why we've chosen to feature women who aren't actresses and models, and also to tell a bit of their story. So it's not just that you see them having a great time in the advert - you also meet Julie in the Zumba class, and hear how she felt really inhibited when she first went and how she has a really touching work life as a nurse, but this is how she de-stresses. When you see that side of the story too, then you start to think... 'I could do this too'."

Other barriers, like cost and family commitments, are acknowledged, but the message digs deeper. "I wouldn't want people to think we don't take the practical barriers seriously too," says Price, "and we invest lots of resources in tackling those, and there are ample women, particularly those who have jobs and children, for who time is always going to be an issue.

"But I think we can put on free sessions and offer creches and give people a really wide range of fitness choices, yet if in your head you're still thinking, 'There's no way I'm going to take my clothes off and put on a sports kit', then none of that is going to make a difference, and I think that's fundamental."

Price admits that she cried when she first saw the final edits. "I've been working for a very long time; I'm 55, and this is the thing I've done at work that I am proudest of. It's already making a connection with people, because it really reflects what it feels like to overcome something, and to feel, 'No - exercise is great!'. And it is joyous. I think it's something that's been missing, particularly for women, in sports and exercise, so I just really hope other people like it."

It is what's been missing, and I felt emotional when I saw it too. And something tells me I won't be the only one...

:: To find out more, visit www.thisgirlcan.co.uk