The F45 workout schedule looks madly exciting; its website is like an ice-cream counter, tons of different classes with zingy names – Brooklyn, Panthers, Hollywood, Romans. Plus, they all have groovy graphics and you think, “This sounds exactly me. I would like to improve my combat prowess while working on my core strength. I want an infamous, 1,000-calorie-burning cardio workout.” They’re on to something, goddamn them. The idea is quite simple – all the workouts a person could do, boiled into 45 minutes, fancied up with themes – and through some combination of variety and enthusiasm, they lull you into thinking it’s actually something you want to do.

I rejected everything that required a partner (Wingman, which is paired resistance; and 22, which is paired cardio, because I am not here to make friends). Foxtrot is an EPIC (their capitals) cardio workout with two intensity levels: a 45-second set and a 20-second one. The idea is that you are more measured in the longer burst, then go flat out on the shorter one.

Picture the scene: you need to do 10 Russian twists (sitting on the floor with your legs up and your back almost straight, putting an imaginary ball to one side, then to the other) and 10 mountain climbers (in a sort of push-up position, then you make a climb-style motion with your legs). It reminds me a little of British Military Fitness: these exercises feel classic, as though they were devised by the Canadian air force around the time they invented planes. The truly distinctive thing about them is how much easier they look when other people are doing them. The very idea that, after 45 seconds, I would start over and do it more vigorously was fanciful. For the 20-second slot, I was pretending.

Jumping jacks, lateral dips, all manner of evil crunching; the main obstacle you’re working with here – hefting about, buckling under the weight of – is your own body. I will say one thing for the short burst; at least it stops. The relief of a thing, stopping, occurs more than once a minute. But then it starts again, so you know, swings and roundabouts.

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Circuits are good for the short-of-concentration-span, but this wasn’t varied enough in arduousness. Some of it needs to be easy. I’d like a nice, gentle bicycle (lying on your back kicking your legs in a horizontal Miss Marple fashion, not a literal bicycle) every once in a while, maybe once every four minutes. Yet this has been crafted with such concerted instrumentalism – not a second wasted, results you could put on a billboard – there were people in the class who’d have probably complained if the nausea had let up.

I’m reminded of the economist Ha-Joon Chang’s critique of productivity: not everything has to be efficient. If someone played a minuet seven times faster, could we call that better? I can’t be sure, but I would have been happier with a foxtrot twice as long and half as hard.

What I learned

It’s meant to be quasi-social, hence the paired sessions. On Saturdays, there is a DJ.

• Go to f45training.com to find your nearest studio