If, as influencers like to say, life happens outside your comfort zone, I had already done a lot of living before most people had left for work on Wednesday morning.

As a new recruit to Lagree Pilates, the high-intensity workout beloved by Jennifer Aniston and Rihanna, not to mention former First Lady Michelle Obama, I was ready - though not quite raring - to go at 7am.

My trepidation, which set in as I made my way to Chelsea where MAD Lagree Fitness Studio, the capital’s only Lagree studio, is located, was fuelled not just by the fact I hadn't exercised in weeks but by the embarrassing memory of my first (and last) Reformer Pilates class.

Thanks to my poor coordination, I had spent the entire class at least two moves behind everyone else.

Now, Lagree wasn't Reformer but something altogether different, I had been told, but on entering the brightly lit studio filled with 'megaformer' machines, I found it hard to imagine what the difference might be. 

Monique Rubins testing her lunging before the 7am class at Chelsea's MAD Lagree Fitness studio started. She was given a tall, lamp-like prop to help her balance

Ten feet long and four feet wide, with a rolling carriage between two fixed platforms and four cables attached, the megaformer looked a little too familiar. 

Fortunately, just as I was mulling making a quick exit, Nour, one of MAD's 10 Lagree instructors appeared - and her enthusiasm for the LA-born (of course!) fitness phenomenon was irresistible. 

Let's start with the benefits. Lagree, created by French practitioner Sebastien Lagree, involves repeating a series of slow and controlled movements, which, unlike Pilates, are designed to work multiple muscle groups at once, while focusing on the core.

As a result, your body doesn't just burn energy when you're moving, but it continues to do so when you've stopped. Good news!

More simply, from building strength to activating slow twitch muscle fibres - the ones used by long-distance runners - Lagree is a one-stop shop for sporting success. Great!

What really did it for me, though, was the fact that it would be brief (classes usually run for 50 minutes). Excellent!

Chat over, it was time to get going. With each of us standing on one of the stationary platforms at the end of our megaformer, Nour started us off with some shoulder rolls and gentle stretching while she explained how to change the springs for greater intensity. 

Then, after she wished us good luck - motivating for some, anxiety-inducing for others - the pace picked up and the 80s hits started playing. 

The plank, which challenges your entire body,  was a recurring movement throughout the class

The MAD Lagree Fitness in Chelsea is the only licensed Lagree studio in London 

With Whitney Houston's 'How Will I Know' blaring, we were told to get into a plank with our elbows on the front platform and then slowly draw the moving carriage in before pushing it back out again. 

Encouraged to move as slowly as possible, it wasn't long before the burn set in and my whole body was trembling. To put a positive spin on it, I had 'accessed those Lagree shakes'. 

But whilst I had been buoyed by the fact that the class would be quick, I soon realised that brevity also had its downsides in this context, namely, that there would be no breaks between exercises. 

After a series of core exercises, the focus shifted to the lower body. As someone who finds lunging on firm ground challenging, lunging with the back foot on a moving carriage wasn't going to be pretty.

Luckily, Nour was on hand with a tall, lamp-like prop which I could hold onto for stability as I pushed back into my lunge. 

By the time we got to the upper body the Eurythmics were playing and, not least thanks to our instructor's inexhaustible enthusiasm ('Nice work!' and 'You've got this team!' turned out to be very welcome refrains), I was completely absorbed in the workout. 

Bicep curls using the cables attached to the megaformer were one of the highlights of the class. Told to press the cables back to activate the back muscles, I could feel the front of my body opening up, releasing tension and supporting good posture. 

And then it was back to the plank. Told to 'hold it to the finish line', I held firm as Nour counted us down from 10 before collapsing onto my megaformer. 

Bicep curls using the cables attached to the megaformer helped  activate the back muscles, opening up the front of the body to release tension and support good posture 

By the end of the class, Monique had mastered lunging while keeping her balance

The class finished as it had started, with some stretching, as well as a loud, well-deserved round of applause.  

Sure, I had taken some (unauthorised) breaks, and I had certainly taken advantage of opportunities to 'shake it out', but I could feel in every part of my body that I had worked hard - and I'd had fun!

If I needed any further proof that I had reaped some benefit, that came the following day - and the days after that - when the burning in my thighs made it difficult for me to walk normally and I had a hard time getting up from a chair. 

But, as far as I'm concerned, that's what you'd hope for from 50 minutes of planking, pulsing, lunging and more.

With a drop-in class priced at £35 Lagree isn't cheap, but you really do get the super-efficient, full-body workout that's promised. 

Would I go back? Absolutely. I just better not leave it too long!

• To find out more about MAD Lagree fitness studio, visit: https://letsgomad.com/