There are plenty of kids razzing around on mountain bikes, but I never thought they ever used them for their intended purpose.

I've always thought of mountain biking as a sport enjoyed mainly by men in their 20s and 30s. They can afford the £1,000 mountain bikes and expensive must-have gear, and they can get out of the city to find what in this country passes for a "mountain".

Of all the European cycling nations, the British are unique in their perverse proclivity for mountain bikes. What we really should buy is a standard hybrid or perhaps a Dutch-style city bike with sensible dynamo lights and hub gears.

Mountain bikes are useless in the city, especially with front suspension which absorbs every ounce of energy you push into your pedals. And kids, having no buying power, always fare the worst.

They get lumped with dreadful £79.99 jalopies from supermarket-style warehouses, "mountain bikes" which would crack at the sight of a real mountain and which are never intended to last a week beyond their one-year guarantee. So I was surprised to learn of a thriving teenagers' mountain biking scene in Oxford. You know those weird hummocky lumps on Shotover? Well, they aren't relics from the Second World War - they're actually made and used by kids. "Yeah, 4 real."

I was alerted to this, and to the plight of our mountain biking youth, by Clive Calliss, a keen (though mature, at 49) mountain biker. He noticed kids using the jumps and ramps at Shotover and realised they needed properly managed facilities.

It turns out that the kids don't really want to hike all the way to Shotover for their two-wheeled thrills and spills. What they want is somewhere nearby. And Calliss thinks he's found the perfect spot. Already kids from as far away as Blackbird Leys cycle to Quarry Hollow for the jumps, and Calliss plans to turn part of the area into a "pump park" for teenagers.

"Quarry Hollow is a wonderful place for general recreation and a large part of it is considerably underused," he told me.

I never knew such a thing as a "pump park" existed. If, as I did, you need a technical update, here goes: a "jump park" is what they've built in Shotover. You pedal around and do jumps off, say, four-foot berms. A "pump park" is similar, with a series of undulating humps in a large circle, shaped like a huge sine wave.

Once you get going, the idea is that you don't have to pedal at all - and you can keep going for as long as you want. You push down the humps and lift up the other side, using your kinetic energy to build up speed. I guess it's a similar principle to when you swing your legs to keep going on a swing.

Calliss hopes that plans to build the pump park in Quarry Hollow will come to fruition this week, as he and the kids want to see the park up and running for the summer holidays. The city council and Friends of Quarry back the plan, so I hope it goes ahead. I wonder whether they'll let "big kids" like me have a go as well?