My butt hurt and my hands were numb. But I experienced a rush of euphoria as my bicycle odometer turned 100 miles on Sunday. I was just short of the intersection of Old Las Vegas Highway, Old Pecos Trail and Rodeo Road on the far south side of Santa Fe. It was about 6:30 pm—making me one of the last people to finish the Santa Fe Century.

Eleven and a half hours earlier, after scarfing down a Dr. Atkins nightmare of a high-carb breakfast (blue corn pancakes and sausage slathered with syrup), I left the St. Vincent's Hospital parking lot in a group of several hundred bicyclists. We cruised down Botulph Road, turned right on Siringo Road, left on St. Francis Drive and right again on Zia Road, taking up all of the right-hand lane in a fashion not unlike a Critical Mass rally.

Before we even left town, there were several flats—the result, no doubt, of our region's notorious goatheads. At Cerrillos Road, we turned left and headed to the exit of NM 14 toward Madrid. As I had learned during a practice run to Madrid a few days earlier with the SOBs (a local biking club called Seniors on Bikes), I paced myself as we headed across the broad prairie, past the state prison complex and the county jail, past Turquoise Trail Charter Elementary School, the Lone Butte General Store, San Marcos Arroyo and the upturned sandstone beds known as the Garden of the Gods.

Most of the group, especially people my age (64), turned left on Santa Fe County Road 42, heading for the village of Galisteo and back to Santa Fe, for the 50-mile run known as the "Half Century." When I rode the 50 miles a few years ago on a heavy trail bike, I pledged I would do the full 100 as soon as I could afford a new road bike. A month ago, I purchased an Orbea carbon-fiber-frame bike with top-notch gears and brakes from Sirius Cycles in Rodeo Plaza, modified for me (a longtime bicycle commuter on a single-speed) by the owner Clemente McFarlane. The bike handled superbly.

I took my initial break at the first of five food, drink, toilet and maintenance stops at the Madrid ballpark at the 25-mile mark. It was there I saw the first rider give up and call for the sag wagon to take her and her bike back to Santa Fe. "I'm just so out of shape," she said. From Madrid, we climbed over the foothills of the Ortiz Mountains, then descended to the second stop at the bottom of a steep climb over the San Pedro Mountains—what is known as Heartbreak Hill for good reason. Like most riders, I walked my bike up most of the steep hill.

The terrain leveled out after the crescent and we descended into the flat prairie. I was making good speed (up to 30 mph), but most of the pack were now so far ahead that I no longer could see them. I had appreciated the camaraderie, but took the opportunity of solitude to stop by myself in the shade of a lone pine near the halfway mark. I turned left just beyond the village of Cedar Grove and headed due east on a long, flat, slightly downhill straightaway for about 10 miles to Stanley, then headed north again into the Galisteo Basin.

Although I had splurged on new gel-padded bicycling pants and gloves, my sit (or sitz) bones at the base of my pelvis (or at least the tissue surrounding them) were aching and my hands were growing numb. As experienced riders had suggested, I stood up on my pedals to relieve the pain on my backside and shook, stretched and tapped my hands (one at a time) to keep the blood circulating well.

There were only a handful of riders at the Galisteo stop by the time I arrived. One of them was David Gebhardt, 48, of Santa Fe who was riding a Cannondale trail bike outfitted with what he estimated were 12 to 15 pounds of accessories—extensive lighting powered by a central battery, mirrors, a bell, his cell phone, glasses and other personal items in special compartments, a first-aid kit and a small ice chest for snacks. He said he had ridden the Half Century in 2012, but this was his first time to ride the full 100 miles—actually 103.

From Galisteo, I pedaled north to US 285 at Lamy where I faced another killer hill. Two sag wagons passed to offer me a lift back to Santa Fe, but I declined. The sag wagons picked up about 100 of the 2,500 riders, ages six to 87, in the 29th annual Santa Fe Century. The largest portion, 57 percent, were from New Mexico, followed by 33 percent from Colorado.

About half of the participants rode the full 103 miles. A bicycle collision in the far southern end of the county sent one man to the hospital with broken ribs. But otherwise the event came off well. Many longtime participants commented on how helpful and friendly this year's Century was.

At the turnoff to Eldorado, one of the Century crew members informed me they were going home at 6 pm, so I would find no one at the last rest stop (on Old Las Vegas Highway, just beyond Interstate 25) or back at the hospital parking lot.

After the jubilation at the 100-mile mark at the Old Pecos Trail, I avoided a trip back to the hospital and headed straight along the easternmost section of Rodeo Road—one of the least bicycle-friendly routes in Santa Fe with two narrow lanes and tiny shoulders that occasionally disappear altogether. I hopped on the Rail Trail, happy to be away from motorized traffic for the first time all day; cruised to Zia Road and crossed where Suzanne LeBeau was killed by a Rail Runner train on April 19. I took a final turn onto Candelero Street to my home.

I was satisfied but so exhausted I could hardly talk. My wife Stacy Brown brought me a large iced water, cut up a mango and drew me a hot bath. I messaged my two daughters, Magdalena and Carmen, who were worried how their father would fare on this arduous trek. Then I went to bed with a smile on my face.

Will I do it again next year? Maybe, but 50 miles will be enough.