Call it the revenge of the middle-class, middle-aged women.

A recent report found that women aged between 40 and 50 are doing more exercise than women half their age. According to a UK study by Vitality, one in four women approaching perimenopausal age are doing exercise almost every day. By contrast, a fifth of those aged between 20 and 29 do anywhere near that.

At The Method, a new fitness studio in west London, this rings true. “Some of the women who come here are completely out of shape,” says its CEO, Katie Henderson. “Perhaps they just had a baby, or are trying out exercise for the first time, but they’re not always your typical gym bunnies – and a great deal of them are in their 50s and 60s.”

The exercise studio is small, hot and bathed in a pink light. Standing at the front, an instructor called Julius shouts the word “mobility” at a class of six women. It’s not the first time the 45-year-old former dancer has used this word to motivate. Mobility is a key tenet of yoga, barre and pilates – and Julius’s other job is teaching pilates to The Lion King cast to prevent injury.

But among the high-end gymwear and rose-coloured weights, the word is unexpected. Fitness classes are generally seen as being for the young and lithe – not the middle-aged and immobile. “It is about fitness, yes,” he says. “But it’s also about keeping up bone density, about building strength and about not getting hurt.”

Across all ages, fitness is big business in the UK. From budget gyms such as PureGym and The Gym Group to pricier, class-focused clubs Barry’s, SoulCycle and Frame, the entire industry is expected to reach £2.8bn this year.

The Method is one of a new line of smaller specialised gyms – New York and LA are leading the way – attracting older women.

There is no one method at The Method; rather the barre, pilates and yoga-based classes lean towards dance and having a good time, Henderson says. “But they are also geared towards all ages.”

Pvolve, a pilates-inspired fitness regime, is more about strength and conditioning. In effect an at-home, low-impact resistance workout, it launched five years ago, but since recently placing Jennifer Aniston front and centre of its campaign, it has blown up in the US and is gradually making its way to the UK.

Using a numbered mat, a resistance band and exercise ball, it looks somewhere between Twister and a tax return. But it is marketed at the time-poor, and those who can’t quite bear the idea of going down the gym for “fear of judgment around physical ability or body image”. Capitalising on the success of the post-pandemic “workout-from-home”, classes are run online, the tantalising carrot being the menopausal-yet-honed body of Aniston, 56, who has claimed “this changed her life”.

Josh Davies, a personal trainer who trains the cast of Bridgerton, thinks the motivation for working out is changing. “Five years ago it was about looking lean, but we’ve moved past aesthetics and I’d go as far as to call it a complete switch in mindset,” he says.

Strength training is a “huge focus, particularly of premenopausal, middle-aged women. It’s not something people talked about until recently.”

Most of his clients are over 40. But, while reformer is punishing, and yoga borders on philosophical, he thinks strength conditioning is as much about injury prevention as anything else, “particularly when clients already exercise – or have either just returned to it after having a baby or haven’t done it in a while”. Studies have shown that while strength-training-focused classes can help slow muscle mass and strength deterioration, older adults improve with a trainer.

Late last year, Jane Fonda launched a four-part series of workouts for Supernatural, Meta Quest’s virtual reality (VR) fitness platform, which focuses on strength training. “When you’re younger, working out is a choice,” she told Women’s Health. “When you’re older, working out is an absolute necessity.”

Exercise among the middle-aged has undergone a loose rebranding in the past few years. The NHS guidelines now recommend strengthening activities twice a week for adults up to the age of 64. Ranging from pushing a wheelbarrow to weights and pilates, solid advice about exercise has historically been difficult to separate from the pressure to diet or look slim, says Davies.

The generational shift is partly about time, but – like many classes – are “also because people can’t afford a personal trainer under the age of 40,” he says. Classes at the Method also cost about £35 each. But when you reach a certain age, he says, mobility is the new priority.