Denny’s wife really didn’t like the idea of him mountain biking. "But she's out of town," he said with a smirk as he removed his three prosthetic limbs. I was volunteering at an adaptive mountain-bike clinic where people with varying physical disabilities spent the day riding four-wheeled mountain bikes. Like most Colorado rides, this one began with climbing accompanied by the kind of stunning scenery that causes uphill endos. Some riders powered up the hill using hand cranks, while volunteers towed others. At the top, one by one, riders took off down the singletrack until it was finally Denny's turn.

He took a big breath, let go of his brakes and descended into the trail. After weaving left and right between evergreens and stone, he paused with indecision at the top of a steep rock slab. Our group collectively held our breath as he shifted his weight forward and committed to whatever outcome awaited him. For just a moment, the air held the type of silence that draws people like us into nature time and time again. Cheers filled the quiet void when Denny nailed the downhill. When he missed the next turn and wedged himself and his bike up against a tree, the clamoring faded until it was met with the sound of a grown man giggling.

"Can I get a hand?" Denny asked with two wheels still dangling in the air. When the other riders responded with an obligatory golf clap, it was oddly comforting to know that mountain bike rides will always be filled with people willing to bust your balls, even if you're down to one limb.

Dave, a paraplegic rider, was a longtime mountain biker out for his first 'post-accident' ride. At the bottom of the run, he pumped his fist in the air and started making his way up for another pass. Molly, who lost a leg years ago, ripped through the trail with fearlessness and finesse, but had to leave early to go rock climbing.

When asked if I wanted to give one of the quad bikes a try, my answer was a given. I've ridden track bikes, trials bikes, and even an awesomely crap-tastic cruiser outfitted with a banana seat and motorcycle fork. I've flailed on unicycles, glorified Big Wheels and the beloved affront to humanity known as the Sh*tbike. If it has wheels, it's only a matter of time before I throw a leg over it–and this bike was no different. Well, except for having four wheels, hand cranks and a riding position dissimilar to any I'd experienced before.

The bike felt simultaneously familiar and foreign, a reminder of the bicycle's endearing ability to be reinvented over and over again, always offering new surprises right when it seems like there's nothing left to learn. With one fist in front of the other, I turned the hand cranks and headed up the hill our group had ridden half a dozen times. My burning biceps quickly revealed a whole new way I suck at climbing on a bike.

When I finally crested the hill, I stared down a trail I've ridden hundreds of times before, only to see a stranger made out of dirt and rocks. I'm not going to say that I was cocky when I first mounted the bike, but I wouldn't be wrong if I did. Somewhere rattling inside my brain was a confidence that hubris mistook for knowledge. I'd been mountain biking for two decades, so this should be easy. After all, if Denny could do it, so could I, right?

On a typical bike, there's a lot of space between your face and the dirt, a distance we often only think about when the former makes an unplanned trip to the latter. With both legs tucked beneath my arched upper body, my head led the charge barely 2 feet above the ground. The fecund smell of loamy dirt swirled through my nose, while my eyes were overwhelmed by the texture of the trail. Buff, rounded rocks became sandstone riddled with thousands of divots. Below me, red-brown striations formed a mesmerizing kaleidoscope in clay.

It was incredible. And scary as hell.

I dove in, terrified and exhilarated as my tires brushed both edges of a trail that had seemed plenty wide earlier that morning. The first turn felt like a trust fall as butterflies rose in my stomach and I waited for my two-wheeled instincts to take over. My upper body struggled to take over actions typically assigned to my legs. Every rock bed and rippled sliver of dirt extracted a grit-catching grin and a few phrases my grandmother would describe as "colorful." As my wheels teetered over the edge of the rock slab I'd watched Denny drop earlier, I got off the bike and walked down.

Long after the invincibility of youth was packed away with my Milli Vanilli mix tapes and Hypercolor shorts, I sometimes find myself questioning what would happen if life as I knew it changed. I can barely remember a time when my sock drawer didn't overflow with bike socks and my tan lines actually resembled a bikini. Everything from my closest friends to my unexpected career entered my life by way of the bike. Even my peace of mind is maintained through hearty courses of dirt therapy.

As hard as it is to imagine life without mountain biking, the reality is that there may be a day when my wheels can no longer grace the dirt. With any luck, that time is still many decades away. And who knows, maybe one day my passion for trails will migrate to a different activity, like professional housecat racing. I don't see that happening anytime soon, but you never know. After all, housecat racing does sound pretty awesome.

I don't know what the future holds, but I know that as long as I'm able and willing to adapt to the challenges ahead, the ride may change, but it doesn't have to end.

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