I tried the Megaformer Pilates workout, loved by Kim Kardashian and Michelle Obama. It targeted my thighs in a whole new way.

The Megaformer class, in affluent West London, took place in a dark studio illuminated by red lights. I work out most days, but my thighs were burning.

• The Megaformer, beloved by endless celebrities, is like a souped-up Pilates reformer.
• It provides high-intensity, low-impact workouts using spring-based resistance.
• I tried a Megaformer workout class and was really tough, even as a fitness reporter.

To me, the word "Megaformer" conjures up images of a monster robot toy made for children, advertised in a booming man's voice.

But this isn't child's play.

A Megaformer is a fitness machine akin to a Pilates reformer, but souped up. Created by trainer to the stars Sebastien Lagree and patented in 2006, the Megaformer uses spring-based resistance to challenge the body with plenty of time under tension.

The list of Lagree's celebrity fans is long, including, reportedly, Jennifer Aniston, Meghan Markle, Kate Hudson, Jennifer Lopez, Michelle Obama, and Kim Kardashian. The workouts started in the US but are now available in the UK, where the industry of boutique fitness studios is booming.

The global boutique fitness studio market is currently valued at $55.16 billion and is expected to reach $79.66 billion in 2029, according to Research and Markets. In big UK cities, at least, demand for luxurious ways to workout is staying strong despite the cost of living crisis.

I'm a health and fitness reporter, and I exercise most days a week doing both a mix of strength and cardio workouts, but the Megaformer was tough. While I've done reformer pilates before and used to do lots of barre classes, I haven't done any low-impact high-intensity workouts like Pilates for a couple of years since I moved out of London.

The burn was real and my inner thighs felt it in the days afterward, and, seeing as I don't normally do Pilates-style workouts, the class reminded me how important it is to vary your training for overall fitness.

The gym was luxurious but minimalist, with club-style studios

There are a couple of fitness studios in London offering Megaformer workout classes now, both at £35 ($45). I went to Studio Fix in Kensington — an affluent area that has no shortage of bougie boutique gyms — where the gym's other classes cost £25 ($32).

The entrance has a minimalist, modern, and industrial interior (think exposed pipes on the ceiling) with gold and chrome accents.

I checked in for my class at the reception and glanced at the protein shake menu. £7.50 ($9.50) each... Perhaps a luxury I could go without.

The changing room had Dyson hair dryers and straighteners, deodorant, dry shampoo, hair spray, and hair ties, as well as Aesop toiletries.

Unlike the other light, bright studios in the gym, the Megaformer studio is decked out in mirrors and red lights with no windows, creating a club-style atmosphere.

The machines look pretty daunting: They're huge, with various handles and straps and a moving "carriage" with different markings that slides forward and back.

I got there early so the class instructor, Andrea, could talk me and the other newbies through the basics. She told me and my five classmates (glossy, slim women in their 30s and 40s) we might find it hard on our first attempt. And she was not wrong.

It's all about time under tension

The class started with some core work and at first, it felt pretty manageable. But that core work went on, and on, and as it did, my abs fast began to burn and fatigue. There were pikes, planks, and lots of pulses.

Megaformer workouts feature a lot of small movements as well as bigger ones with a larger range of motion, and you're meant to do each movement super slowly (think four seconds down in a lunge and four back up) to maximize time under tension. It sounds easy. It was not.

As Lagree himself previously told me, moving slowly means you can't employ momentum to lift a weight.

"You will get a better response from working out because you will activate more muscle fibers. When you're just using explosive movements, you're only activating mostly the fast-twitch muscle fibers, which are responsible for building bulk."

Andrea shouted instructions and demonstrated each movement throughout the class, which meant I didn't feel clueless. I welcomed any breaks she took to demonstrate each movement first, otherwise there'd have been zero rest.

After the core section was over, we moved on to the lower body and performed a range of exercises on one side using the straps and cables before repeating on the other. We never had to do any one exercise for too long, but it was still plenty long enough to burn. Many of the exercises looked easy, but were surprisingly painful — in a good way: my muscles were burning and began to shake as I worked them in ways I wasn't used to.

The final section of the workout was upper body. It was also the easiest and the shortest, and I'd have liked it to be longer.

The class was too expensive for me to do regularly

The class went by quickly. Afterward I felt proud of myself and my body felt good from the stretching and mobility.

That afternoon and the days following, the body part where I really felt sore was the inner thighs, which reminded me that I mustn't neglect them in my own training.

It was also a good reminder of the importance of variety in exercise. You can be squatting twice your bodyweight but unable to pulse in a lunge on a Megaformer for 15 seconds if you never do it.

I wouldn't do solely Megaformer classes, as it's important to do heavier strength training and cardio too, but it would be a good addition to my workout regime if my budget allowed.

When I asked Studio Fix founder Najeeb Abunahl why the Megaformer workouts cost more than others at the studio, he told me it has to do with the licensing agreement they have with Sebastian Lagree to use and train on Megaformers.

"We also bring a Master Trainer from Europe to certify all of our instructors in the Lagree method," Abunahl said.

Unfortunately for me, the price tag is just too high. But if I had cash to splash, I'd go back for sure.