What is it? Walking between two points along a suspended line of webbing. It’s tightrope walking, essentially, but apparently easier.

How much does it cost? If you’ve got trees to anchor your line to, you can get a 15m kit for £45. If not, you can buy a self-contained unit called a Slack Rack for about £250. Or, if you’re really lucky, you’ll find it at your gym.

What does it promise? Improved balance and core strength, which will in turn improve your posture. It’s also meditative: if your mind wanders from the task at hand to thinking about your tea or a funny picture of a cat you saw on Facebook, you’ll almost definitely fall off.

What’s it actually like? The internet is full of spectacular slacklining images, of people doing handstands on their slacklines, people doing the splits, people slacklining their way across colossal canyons. I did not do any of this. I just tried walking across a Slack Rack five inches off the ground in a south London gym. And that was enough. My sense of balance is so legendarily bad that I managed to fall off the slackline before I’d even put both feet on it. Gradually, with lots of hints from my trainer – slow down, concentrate, engage your core, stretch your arms out and use your upper body as a counterweight – I got a little better. But not by much. I don’t know how slackliners do it. Is it magic?

Best and worst bit Theoretically, slacklining is a huge amount of fun. Realistically, though, it’s just maddeningly hard.

Is it worth it? If you like being reminded of your basic frailties in the most frustrating way imaginable, be my guest.