Properly supervised, they are great ways for kids to burn off all that excess energy that drives us parents bonkers when they strut around our living rooms like caged tigers after school. They also teach our children discipline and self-defence.
But the bright sparks of the Greenlands Labour Club in Preston, Lancashire, have taken the caged concept to another level - as our recent news story shows all too horribly.
Ladies and gentlemen, for your entertainment and delectation, may we present to you The Cage-Fighting Eight-Year-Olds.
It's unbelievable isn't it?
Yes, boys brawl. It happens in playgrounds up and down the country each and every day to resolve minor disputes between lads and to establish who fits where in the pecking order.
Yes, boys fight. In thousands of school gyms and sports clubs throughout the land, youngsters are getting to grips with each other in half-nelsons, armlocks and cobra clutches as they go about learning and practising the ancient sport of wrestling.
But now, the wise men of Greenlands have put these realities of life together to create the brand new sport of Cage Fighting For Boys.
There is nothing wrong with boys fighting per se. As parents, we love rough-and-tumbling with our kids, comparing them to lion cubs. We want them to grow up physically fit and strong, able to look after themselves. Some boys will progress this to a competitive level and one day will be hero-worshipped by an adoring nation for winning an Olympic Gold medal in their chosen sport.
But little boys fighting for the entertainment of adults is not just wrong, it's sick. Apparently, a crowd of 250 watched two little lads kicking, shoving and grappling each other to the floor, many of them tanked up on alcohol.
What must be going through the minds of people who enjoy seeing children hurting each other? If they see a couple of kids fighting in the street do they, a) break it up and get the kids to shake hands, or b) start clapping and whooping and screaming at the tops of their voices: 'GET IN THERE, SON. DO HIM! TAKE HIM DOWN!'
The argument goes that the boys don't damage each other because no punching or gouging is allowed. But doctors and child safety campaigners said the fact the children weren't wearing headguards could cause brain injury or death.
To me, that's over-dramatic hyperbole. Boys are more likely to suffer a head injury by cracking their skulls on a hard playground surface during a game football.
It's the emotional damage that is more concerning. One little boy was reduced to tears and had to receive medical attention: what impact will that public display of emotional embarrassment have on his psyche as he reaches adolescence?
And what a thing to one day realise about your own father, the very man who is supposed, above all other things, to protect you.
Imagine the conversation with the therapist 20 years from now.
Counsellor: 'So, Big Billy, what happy memories did you have of you and your father when you were growing up?'
Big Billy: 'I remember the bulging veins on his neck and his bright red screaming face, amongst a sea of others, as he yelled at me to 'PUNCH THAT OTHER CHILD'S LIGHTS OUT!'
Yeah, good job, Pop.
I'm not a wet-lettuce liberal who believes all physical contact between children should be banned. I come from a family of boxers. My grandfather was a heavyweight champion in Manchester; my dad boxed; my three younger brothers boxed. We come from the same council estate as Ricky Hatton.
But I never boxed. I got in the ring once, felt a punch on my bony nose, and got straight out again. My dad didn't cajole me to Get-Back-In-You-Softie-AND-DO-HIM!
He said: 'That's not for you, son. But at least you gave it a go.'
Oh, and I was 13 at the time. Not eight years old.
I'm just grateful that I didn't inherit that boxing gene, and I'm glad my seven year-old son hasn't, either.
He came home from school the other day and asked if he could take dancing lessons. And of course, I agreed.
Where's the harm in dancing? But hang on, I've just had a thought: what if he's any good and one day ends up on Britain's Got Talent?
Humiliating himself in front of an audience of thousands of baying adults.
What do you think of this new 'sport' and the people who watch and allow their children to take part?