Andrew Taylor discovers the highs and lows of summer bike riding through winding Aspen valleys — and lives to tell the tale.
For someone whose heart feels like it's about to stop, I'm having too much fun.
My legs are burning, my lungs are bursting and my shirt is soaked with sweat as I slowly peddle past the US Forest Service welcome station towards Maroon Bells, one of the US's most photographed peaks.
In contrast, our guide Damien barely raises a sweat as he glides effortlessly up the steep road, which has a steady stream of cyclists peddling along it. At more than 2500 metres above sea level, we're already far above Aspen, but still 300 metres below Maroon Lake.
Aspen might be known for its snow, but in the summer months tourists and locals of all cycling abilities take to two wheels to climb the steep mountains and hurtle downhill at breakneck speed.
The 10-kilometre journey along Maroon Creek Road from Aspen, past Aspen Highlands ski area, to the Maroon Bells scenic area is one of the region's most beautiful and safe cycling routes.
Apart from the public bus ferrying the less energetic to Maroon Valley, the winding Maroon Creek Road is closed to most types of vehicles.
Shaded by groves of aspens, the road follows Maroon Creek through the Maroon Valley and lush White River National Forest, which is dotted with camp sites, before reaching Maroon Bells scenic area.
Hiking trails criss-cross the glacial valley, through alpine meadows filled with wildflowers such as the columbine, Colorado's state flower, and forests of spruce, fir and the ubiquitous aspen tree. Hummingbirds and jays hover above, while the eagle-eyed can spot elk, deer and mountain sheep.
Mirrored in the waters of Maroon Lake, the 4317-metre high North and South Maroon Peaks tower over the valley, their distinctive red colour and bell shape giving the mountains their name.
Cycling up a steep mountain is rewarding, but the real fun comes when you click the gears to the highest setting and cruise downwards. What cycles up, comes down in double time in the case of Damien and my fellow cyclist Gareth, who have disappeared by the time I take the first bend.
Compared to the smooth, wide asphalt of Maroon Creek Road, the Valhalla trail at Snowmass Mountain is a pile of broken bones waiting to happen.
We've been kitted out with helmets, shin pads, wrist guards and vests with more shoulder padding than Joan Collins' Dynasty wardrobe.
But the sight of one of our instructors, Kate, wearing a metal neck brace - she points to a scar and says she has a $150,000 neck - is not exactly reassuring.
One of the four ski areas in the Roaring Fork Valley around Aspen, Snowmass Mountain's 80 kilometres of terrain become downhill mountain biking trails ranging from gentle roads to hair-raising single tracks during summer.
Besides Valhalla, there's the 4.2-kilometre Vapor trail, which descends almost 500 metres through meadows, over bridges and berms, and groves of aspen and evergreen trees to connect with the Valhalla and the more gentle Easy Rider trails at the top of the Elk Camp gondola.
Our instructors, Kevin and Kate, demonstrate how to make tight turns, ride over bumps and avoid toppling over the handlebars before whisking us up the Elk Camp gondola to Valhalla.
Snaking down the mountain for 4.5 kilometres, the trail is a narrow dirt track through trees and is littered with obstacles - rocks, ruts and roots - seemingly designed to knock you off your seat.
There are also wooden bridges, tunnels and steep jumps to crash into if a tree doesn't floor you first.
Like Valhalla, the nearby Rim trail appears as a thick black line on the Snowmass trail map, which seems to indicate it's for expert riders, yet the concierge at the Viceroy Snowmass hotel assures me it is ideal for a quick tootle on one of the hotel bikes prior to dinner.
Her only advice is to take water: the mountain air is so dry, it turns you into a sultana before you realise.
Thirty minutes later, I'm lying on a circular platform tiled with the yin-yang symbol, my heart pounding and barely able to breathe.
The view of snow-capped mountains plunging into deep, pine-forested valleys is breathtaking. But I need every skerrick of oxygen I can gulp from the thin mountain air after hauling myself up switchback turns to the top of the ridge line.
Hawks circle overhead, probably waiting to feed on me if I pass out, while wasps snap around my head like firecrackers.
Nearby is a rock engraved with a poem extolling the landscape, which I begin to appreciate as my heart rate calms down.
There are no more tough climbs, but the track is narrow and has some hair-raising sections where it traverses slopes full of loose rocks.
The ride up Smuggler Mountain is no less challenging, its bumpy dirt track twisting and turning ever upwards in the full heat of the sun.
This time, I'm saddled up on a mountain bike with gears, suspension and a padded seat that is a lot kinder to my rear end.
But the sheer ascent defeats me and I'm soon pushing my bike like a shopping trolley while Damien waits, not a trace of sweat on his brow.
I'm itching to saddle up and begin the descent on the Hunter Creek cross-country trail.
It's dusty, dirty, wet and strewn with rocks and tree roots - one wrong turn will see you tumble down a ravine or slam into a tree.
It's also utterly exhilarating.
However, not all of Aspen's bike trails require an Olympian's level of fitness. One of the most enjoyable rides is also one of the easiest: the Rio Grande trail to Woody Creek Tavern. It is famous for being the favourite watering hole of gonzo journalist Hunter S. Thompson, who lived for years in tiny Woody Creek (until his suicide in 2005) and even once ran for sheriff of Pitkin County.
Beginning at Aspen Art Museum, the Rio Grande trail meanders alongside the Roaring Fork River to Woody Creek and further on to Carbondale and Glenwood Springs.
The trail is asphalt, wide and mostly flat, and shaded with aspens, firs and other evergreens, which occasionally give way to steep cliffs. There are plenty of places to stop for photos, a rest or to cool down in the river, icy cold with snow melt.
A mecca for Thompson fans, the Woody Creek Tavern is filled with memorabilia and souvenir T-shirts. Better still are the margaritas, topped with enough alcohol to steel yourself for the 40-minute ride back to Aspen.
There's also a free public bus, although its rack can carry only two women's bikes, forcing chivalry upon men whether they like it or not.
Andrew Taylor was a guest of Aspen Chamber Resort Association, Snowmass Tourism and Virgin Australia.
Virgin Australia flies daily from Sydney, Brisbane and Melbourne to Los Angeles, with connecting flights to Aspen on Delta Airlines. 13 67 89, virginaustralia.com.