Just how tough are London's toughest exercise classes? We found out

Nothing good lasts one hour. It’s too short for a date, too long for a dentist’s appointment, and definitely too much time to be spent flat-out sprinting. That’s the crux of Barry’s Bootcamp, which touts itself as the ‘best workout in the world’ and has a cult of celebrity fans. It involves an hour of hopping between treadmills and weights, with pretty much no breaks. I’m already nearly falling over and wiping out the much fitter people on treadmills next to me after the first 15 minutes. By the time I hit the floor to do burpees, I’m slipping and sliding in my own sweat like Bambi on ice, covered in olive oil. Early on in the class, the guy on the treadmill next to me is screaming and I don’t understand why. At 30 minutes in, I’m screaming too, and for the next half an hour I only stop screaming when I think I’m going to faint. Afterwards, my Fitbit tells me that my heart rate was over 100 beats a minute higher than normal.

It’s a staggeringly demanding workout, and definitely not an enjoyable way to spend an hour.

Heart rate: 174bpm

How tough is it? I spend the rest of the day at home, shivering in a blanket.

Various locations. £22. Packages available.

They couldn’t call it ‘squirrels’ or ‘kittens’, could they? Still, ‘bears’ is a pretty accurate name for the growling, gruelling circuit session I’m in for in this Oxford Circus basement, one of a vast number of F45 franchises in the capital. The famously full-on Australian fitness craze has spread rapidly around the world and is gloriously hard work. I’m begging for mercy by my second circuit (of 18). For 45 minutes, we dart around the room doing plyo push-ups, box jumps and side lunges, all dictated by the high-tech screens on the walls. There are no mirrors in an F45, so my only barometer is the people around me, all of whom seem to be struggling a lot less. Still, if Barry’s was hell (flashing red lights, endless suffering), then this is heaven. It’s all white walls, high-fives and, thanks to the handy timers, there’s a nice bright light at the end of the tunnel. Hallelujah!

Heart rate: 128 bpm

How tough is it? I try to do an Insta Story after the class, but my hands are shaking so much that I give up.

Various locations. £25.

It’s day three, and I’m moving like a zombie in a low-budget horror movie. I never want to hear the word ‘squat’ again, but 1Rebel, the go-to boutique gym for fashionable fitness types, has other ideas. ‘Reshape’ claims to hold a candle to Barry’s, and on the surface it’s pretty similar: a split between treadmill sprints and weights exercises. Here, though, the weights bit is basically all core and abs, a crushing blow for a soft-bellied man like myself. And I’m stationed next to Tiago, the sadistic ‘master trainer’ who’s set on making me reach my personal best. As the class hurtles to its end, we switch our treadmills into ‘dynamic mode’, powering them solely with our own momentum. I zoom to 18kmph and prematurely celebrate. Then I stagger down to 15kmph, 10kmph, 5kmph, and collapse on the floor.

Heart rate: 156 bpm

How tough is it? At one point, the photographer has to get me a towel. I’m sweating so much I can’t open my eyes.

Various locations. £22. Packages available.

By my last day, basic tasks are impossible: I’m struggling with the climb to my front door, and I live on the ground floor. What better way to finish me off, then, than a class that is 100 percent climbing? Housed at Anthony Joshua’s swanky BXR, Climb to the Beat puts you on a high-tech ‘versaclimber’ and forces you to, well, climb to the beat – non-stop, for 45 minutes. By the time I really start to struggle, I wince through the pain to see the time on my machine: 4.33. This is going to be hard.  It’s like spending almost an hour simultaneously riding, and being pummelled by, an out-of-control pneumatic drill. Every time I try to stop, the instructor Liberty makes sure I carry on. The only time I do stop, during my second-last sprint, it’s because I’ve been sick in my mouth.

Heart rate: 148 bpm

How tough is it? Like going 12 rounds in the ring with AJ, if he was only punching me in the thighs. 

£15 for members, £30 for non-members. Packages available.

F45 makes me tremble the most. After 1Rebel, I can’t walk. BXR quite literally makes me sick. But nothing reaches the pure crimson-faced agony I experience on day one at Barry’s Bootcamp. The Fitbit stats don’t lie, and neither does my bruised ego or my aching quads. Barry’s really is the toughest exercise class in London.

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