If you’re fit, you live longer, but getting fit is boring. Being bored now is worse than dying at an unspecified point in the future.

Ergo, you give up. This explains why almost half of the 68% of us who make a new year resolution to do more exercise have chucked it in by the end of January. Here, in the depths of February, is where best intentions come to die.

Step away from the cake. I have the solution. It is an exercise class, yes, but it is cunningly disguised as fun. The idea of Rabble, a company with classes all over London, Manchester and, coming soon, Bristol, Cambridge, Chester, Brighton and Liverpool, is to play children’s games. Because children, when you unstick them from their iPads, are very good at exercise. You won’t get them jogging because that’s sooo boring, Dad. But a child will play bulldog or stuck in the mud until you make them stop. Why can’t grown-ups have fun too?

The class tonight is called “the great escape”. There are 16 attendees of varying degrees of age and fitness. We’ll be split into two teams: jailers and prisoners. The prisoners must escape. The jailers must stop them. The prison is a basketball court somewhere north of King’s Cross.

First, instructor Josh (Canadian, excitable) insists on many other games. We begin with tag, and if it wasn’t for the sheer exuberance of the others, I might have felt embarrassed playing a game I last played in 1984.

Instead, I feel only slightly embarrassed. Mainly because there is a lot of high-fiving. I hate high-fiving. I’d rather die sooner than high-five a stranger.

We move on to a variation of dodgeball and it’s deceptively exhausting. Your legs and lungs want you to lose quickly. Your sense of pride won’t allow it. And it’s fun. So much fun. High-five.

Next, British bulldog. There is a man half my age who has made it clear that he is a) quicker than me and b) determined not to let me pass. I run at him, he smiles confidently, I sidestep and off he shoots in the wrong direction. It is the happiest I’ve felt in at least a decade. He spends the rest of the game proving it was a one-off.

This all goes on for 40 minutes. Muscles I haven’t used since the year I last played tag are burning. If I were in the gym, I’d have given up by now. Instead, it’s time for the great escape. I escape twice, then I have a little and entirely involuntary lie-down.

Ninety per cent of those who survive a month of this stick at it for the long haul. Everyone I ask says they’re surprised at their rapid rise in fitness. It isn’t that surprising. High-intensity exercise is the best exercise. And I’ll go back the very minute I’ve got over these shin splints.

45: The percentage of people who reward themselves with a “treat” after working out
Research: British Lion Eggs 2014

joinrabble.com, from £7 an hour

Health hacks: get fit at your desk

Lean in
Sitting, lean forwards until your body is 2in from the desk. Grab the edge and push the chair out until arms are extended. Pull back and repeat 10 times.

Crunch time
Sit straight and arch your lower back. With your hands on your desk, pull your hips beneath your tummy. Hold for five seconds. Repeat 15 times.

Wee fit
Use a loo break to do a set of upright push-ups, with your hands on the wall in front of you at chest height. Do 15 before you unlock the door.

Quiet quads
Sit forwards, away from the backrest, and lift one leg about 3in off the ground. Hold for 10 seconds. Repeat twice on each leg.