What is it? A high-intensity, low-impact group workout performed on hydraulic machines, designed to lower your chance of injury.

How much does it cost? Membership starts at £99 a month.

What does it promise? A high-rep workout that burns fat ridiculously quickly. According to one review, Speedflex gives you “The world’s best bum”. Alan Shearer is a Speedflex fanatic, although I haven’t ever noticed his bum, because I’m constantly distracted by his horrible dress sense and boring voice.

What’s it actually like? In a word, terrific. The 45-minute class is mainly spent continuously performing a small set of movements – military presses, clean and jerks, bent-over rows, etc – on the hydraulic machines. But because the machines respond to the amount of force exerted on them, you can make the class as hard as you want it to be. Better yet, your heart rate is splashed across screens all around the studio, so you always have a visual reminder of when to work harder (if you drop below 85% of your maximum heart rate) and when to ease off (if you get close to 100%, stop being able to feel your arms, and keep making involuntary “nurgh” noises). Add to this excellent instructors, a sense of camaraderie and – importantly – very good showers, and Speedflex becomes something quite special.

Best and worst bit It’s a bit pricey, and there are only four Speedflex centres in the country. That said, I managed to burn a whopping 995 calories during a single class, which can only speak to how preposterously effective it is.

Is it worth it? If you see me in the street, check out my magnificent bum and decide for yourself.