It's been a little more than two years since Boulder cyclist Tom Zirbel served most of his two-year suspension from the sport for testing positive for a banned substance.

He still thinks about that "earth shattering" time in his life, he said, but has moved on.

Zirbel proved that most recently by winning the 2013 time trial national title in May.

This week at the Nature Valley Grand Prix in Minnesota, Zirbel and his Optum Pro Cycling teammates are looking to three-peat by defending Zirbel's 2012 win and teammate Jesse Anthony's win in 2011. And earlier this week, the USA Pro Cycling Challenge selected Optum to compete as one of five continental teams.

But in between training and racing on the national circuit, Zirbel still makes time for local races. He made an appearance at last week's Ideal Market and Twin Peaks Mall criterium in Longmont, a small mid-week race held in the mall's parking lot.

The "gentle giant," as race organizer Barry Lee calls Zirbel, lined up near the back of the peloton and jokingly pulled out his time trial stars-and-stripes jersey from his pocket.

In the end, Zirbel opted to go the more modest route, sporting his Optum jersey complete with bright orange helmet instead.

That's just part of who Zirbel is, said Lee. He's quiet, but not standoffish, and Zirbel is thoughtful, choosing his words carefully. After his dealings with the U.S. Anti-Doping Agency, he exudes an aura of calm maturity while waiting for the race to start.

"He's not a super elitist, arrogant type of cyclist," Lee said. "He's approachable."

Running roots

Now 34, Zirbel grew up in north central Iowa, where he still returns every year for his hometown bike race, the Bicycle Blues and Barbecue Festival in Clear Lake (he won handily last year).

He was a runner by age 12 and a distance specialist at Wartburg College while studying chemistry before a knee injury forced him off his feet.

Tom Zirbel swings wide on a curve as he competes at the Ideal Market WFM Twin Peaks Crit Series on Thursday, June 6, 2013 at Twin Peaks Mall in Longmont.
Tom Zirbel swings wide on a curve as he competes at the Ideal Market WFM Twin Peaks Crit Series on Thursday, June 6, 2013 at Twin Peaks Mall in Longmont. (Greg Lindstrom)

Zirbel had moved to Boulder to run, but ended up buying his first road bike in 2003 to cross train. In the 10 years the followed, Zirbel has learned that cycling, not running, is his calling.

"There's a lot of carryover," Zirbel said, his usual mop of dirty blonde hair cropped short this season. "In endurance athletics, it's all about cardio, and I had built my cardio over 10 years of running. I'm just a bigger person. My running kind of suffered more because I'm so big. I'm 6-foot-5 and almost 200 pounds, and you don't see runners that big.

"With cycling, it's a more level playing field."

Zirbel understands that he's "big boned," hence the nicknames like "gentle giant" and "wattage cottage," and he's not afraid to talk about it.

At the 2013 Tour of California in May, Zirbel joked that his size made it tough for him to withstand the 110-degree heat. He left the stage race early, delirious from heat exhaustion and disappointed.

But that setback may have given Zirbel extra fuel for time trial nationals, which he almost won in 2008 and 2011.

He also finished second at the 2009 time trial championships, a result that was thrown out when, at that race, Zirbel's urine tested positive for the steroid dehydroepiandrosterone, or DHEA.

Suspension 'was like a death'

Zirbel vehemently claimed then -- and still does today -- that he didn't knowingly ingest DHEA, that he must've taken a supplement tainted with the steroid. Zirbel rode for Bissell and had signed a contract with Boulder-based Garmin to begin in 2010.

After receiving his sanction, Zirbel walked away from the sport entirely, but eventually changed his mind. Looking back, it's easier for Zirbel to put the suspension into perspective. People have gone through a lot worse, he said.

For the first few months, he was depressed and not stable, he said. In hindsight, Zirbel said he's thankful his now-wife Rebecca Heck, who rides cat 3 for Primal/McDonald Audi, stuck with him while he struggled.

"It was like a death," Heck said. "He lost his job. It was his identity. But I think that's a great test for a relationship, not to sound too cheesy."

Zirbel's not a "conspiracy theorist," he said. He knows the tests that led to his suspension were positive. But Zirbel said he wishes the U.S. Anti-Doping Agency and other governing bodies of cycling would consider factors like intent and motive in doping cases.

Zirbel worked with the University of Colorado Law School in Boulder and provided the U.S. Anti-Doping Agency with information about two doping cases, which led the organization to lift his suspension about eight months early.

"It's an imperfect system," he said. "You see what's happened in our sport and how many people have gotten away with it, true cheaters. They were perfectly willing to put away a non-cheater for two years. I don't have a great solution, but I think starting with looking at intent is one way to go."

Cycling can 'turn on you'

After the Nature Valley Grand Prix this week, Zirbel already is looking ahead to the USA Pro Cycling Challenge. Though team rosters haven't yet been announced, Zirbel most likely will represent Optum in the stage race.

He still thinks about riding into Boulder for Stage 6 in 2012 and seeing fans five or six rows deep, adding that he's bummed there's not a Boulder leg this year.

"One of the highlights of my career was rolling through Boulder," he said. "It gives me goose bumps just thinking about it."

Zirbel and Heck were married last October, and true to their mutual love of bikes, they rode away from the ceremony on an emerald green tandem. The only lingering reminder of Zirbel's suspension today is that he refuses to take any supplements, fearing that he could ingest another one tainted with a banned substance.

But for the most part, he says he's just another guy in the peloton.

"I don't think about it," he said. "I don't fear it every time I give a drug test. I know who I am. I know what I've done and I have to be comfortable with that and just know the sport can turn on you in a second."

-- Follow Sarah Kuta on Twitter: @SarahKuta.