Getting fighting fit in San Francisco's virtual reality gym

The big difference? You attack the enemy by working out. Black Box VR is an immersive virtual reality gym where you perform exercises and battle it out in a video game against monsters.

As if it wasn't already the most Silicon Valley thing you've ever heard, the gym is across the street from Twitter's HQ on Market Street in San Francisco.

Once inside, a specialist helps you get set up with armbands and a VR helmet. Then, it's time for the AI. The 'gym' part of Black Box VR takes place in a private booth with two cable pulls.

The machine is capable of delivering 120lb (about 55kg) of resistance, and you perform chest presses, squats and rows to battle enemies.

The battle itself is where the AI shines, and where you forget that you're working out. The simplest description is that, in a Colosseum-like arena, you have to destroy your opponent's crystal before they destroy yours. You can unleash attacks by either performing the corresponding exercise or by deploying your forces to attack the enemy. You deploy forces by performing a set of punches and karate chops as fast as you can. The better your form, the faster and stronger your attacks.

Put simply, it's a fun game. The machine the cable pulls are attached to is smart: when it starts feeling easy, it automatically increases the resistance.

You forget you're at the gym and just focus on attacking the enemy as fast as possible. At the end of my 30-minute workout, I'd worked my upper body and felt the same sort of good fatigue I feel after working out at a real gym.

It's easy to be cynical. Why do you have to play a game to work out?

Why can't you just go and lift weights at the gym? Black Box VR's website points out that gyms are full in January and start to empty in February.

Its aim is to "make fitness a habit as addictive as your favorite eSports and video games".

You'd be wise to consider the context in which Black Box VR is coming on the scene. In the US, only 22.9pc of adults aged 18-64 met the guidelines for both aerobic and muscle-strengthening activities during leisure-time physical activity between 2010 and 2015.

That's up from around 18pc in 2008, and represents significant variation between states, but still doesn't paint a picture of an especially active country.

Add that to the fact around 160 million Americans are obese or overweight (roughly half the population), and trying to make working out a game starts to sound like a great idea.

Gamification is one of those buzzwords that everyone tends to nod their head about but not fully understand, a bit like Bitcoin. Think about how easy it is to get lost in a video game, and how we play video games even though we know we could be doing something more productive. Or think about how something might be touted as 'making learning fun' - why is it important that something is fun?

There are a couple of reasons video games are so good at grabbing your attention, and keeping it, and Black Box VR is taking advantage of them.

Autonomy, for one - if you feel like you have the power to move the needle on something, it's more engaging than something that's out of your control. A short feedback loop is another; video games all have points systems, rankings or progress bars, because we're always striving to do a little bit better than our friends. But the bottom line, and why I think Black Box VR could be successful, is that the workout was straight-up fun. I don't feel like I spent a half hour working out. I played through a VR tutorial, and then played two battles against enemies, destroying their crystals. If a gym can make working out not feel like working out, they're on to something big.

Don't get me wrong; going to a virtual gym made me feel like an extra in Ready Player One. As I worked out, I was reminded of the William Gibson quote: "The future is already here - it's just not very evenly distributed."

Gamification is essentially the art of tricking your brain, and if we can channel it in useful ways, I can imagine Black Box VR and its variations becoming incredibly popular. The bottom line? This could be big, and don't knock it till you try it.