What is it? Indoor climbing over relatively small heights, with no ropes. If you fall while bouldering, you really fall.

How much does it cost? I went to Arch climbing wall in London’s Bermondsey, which is a tenner a go or £50 per month. Prices at other bouldering centres will vary.

What does it promise? An aerobic workout, an anaerobic workout, increased strength, flexibility, stamina, balance and coordination. Also, to a much lesser extent, you get to look like Tom Cruise at the start of Mission: Impossible 2.

What’s it actually like? Immediately intimidating. Boulderers are lean and sinewy types, and to see them dangling from ridiculous overhangs by their fingertips is enough to fill you with dread. But an induction is all you need to shake your nerves. You’ll be taught how bouldering works (each wall is dotted with multicoloured handholds, but you need to pick one colour and stick to it), the best practice (try to maintain three points of contact with the wall at all times), the lingo (each move is called a problem) and how the shoes should feel (uncomfortably tight). You’ll then start climbing up the easiest routes, before quickly progressing to smaller grips spaced so inconveniently you feel like you’re playing a game of vertical Twister. If you keep it up, presumably that’s when the sinew comes.

Best and worst bits Complete a tricky set of problems and you’ll feel the most incredible wave of satisfaction. When you go bouldering, your brain is kept so busy you don’t notice how hard you work. Until the next morning, when you do.

Is it worth it? If you like problem-solving and sore feet, absolutely.