Duncan McCallum: 'My brain shouts: brake, slow down, survive'

OF ALL the sports I do, downhill mountain biking is the hardest and most dangerous. It amazes me that, in the last 15 years, Scotland has become one of the best MTB countries in the world. The piéce de resistance is the world cup Nevis Range downhill track.

Seeing the bike warriors in full body armour gathered at the gondola entrance is like watching a scene from Gladiator. Downhillers are a little bigger than the cross-country cyclists. There are more shaven heads and tattoos, and they are more mud-spattered. Despite the tough exterior, there is a general calm in the collective knowledge of shared experience. Despite the raw courage required to hurl yourself downhill on a 3,000 pedal bike, it can be intensely geeky. Every bike is scrutinised for the latest gear or hydraulic brake system. I'm an occasional downhiller. I don't have the ingrained comfort with my equipment; a signal to those in the know that I am just a well-equipped part-timer.

I like padding up. It's a ritual, the musty aroma of sweaty days past; the cuts and scrapes telling tales of near misses. Mountain sport serviced by a ski lift or uplift truck seems overly consumptive, too much metal on the mountain, too much power hauling people up a hill. This is downhilling; electricity, diesel fumes and steel. Whatever the dubious economic benefits there are to running ski resorts in Scotland, they are there, and today I am complicit in their existence.

As the gondola leaves the station and drifts up the hill, I study the course. A third of the way up I give up looking for tell-tale loose boulders, jumps and drainage channels. I'm just filling my head with jumbled information.

I jump on my Iron Horse and the eight-inch suspension sags under my weight. Rolling down to the start of the run, its fat tyres whirr with a great buzz heralding faster times ahead. I let the machine run, feeling the balance, moving its weight below me. Behind the helmet visor, clad in armour, I feel strangely disconnected from the rocks and boulders – until the first slip on the loose surface brings me sharply aware. The rear wheel kicks out on a dusty berm. I instantly feel my brake hand receive an instruction from my overloaded brain: "Brake, slow down, survive," it shouts. But I know to touch the brake would send my body crashing into the granite hillside.

After a minute of pounding, my forearms are screaming from braking. I pull over and catch my breath. I shake out my hands, which are fused shut; it's intensely physical, intensely exciting and very scary. I am surfing a fine line between riding at the edge of my abilities and letting the steed run out of control. I process the feeling of childish excitement and the basic human desire to not hurt myself.

This dilemma is in all adventure sport. There is an addictive balance between the supreme thrill of being alive and a basic sense of self-preservation. The most skilled ride this addiction on a knife-edge between success and disaster. The most balanced accept that to flow close to the edge of supreme performance, pain is a necessary companion. For me, the blade is a little more blunt, but as the bike and I blend for a brief moment on the track, I can hear the sound of a knife sharpening in the background.

• This article was first published in Scotland on Sunday, June 6, 2010