AUBURN – Starting a family. Taking care of sick parents. Organizing a cycling club.

There are hundreds of reasons why competitive cyclists coast away and become weekend warriors, if not abandon the addictive, lifetime sport altogether.

Addictive and lifetime being the operative words.

Sunday’s eighth-annual Great Falls Criterium was an object lesson in the shelf life of competitive juices.

Sure, professionals and serious recreational riders from throughout New England ruled most of the day’s endurance events, contested on a 7/10-mile street course in the sun-splashed downtown.

Then there was Larry Poulin, 45, of Auburn, who celebrated his 12th place finish in the 45-and-over masters division by watching his children race on a makeshift mini-oval and subsequently withdrawing from the 35-and-up race.

After stepping away for nearly a decade from the sport that once consumed his life, Poulin was entitled to soak up the rays.

“We were busy having kids and everything else. It kind of took a back seat. I shouldn’t have done it that way, but that’s just the way it is,” Poulin said. “I’ve been racing a little bit this year. It’ll take me about a year to get back where I need to be.”

Richard Marchessault, 49, followed his teammate Poulin across the line in 19th place. Combined with Saturday’s hilly, lakeside road race, the 20-lap test brought the Lewiston man’s weekend travel log to 57 miles.

Not bad for a guy who was celebrating his comeback from a three-year hiatus.

“I actually became president of the Maine Cycling Club. It takes a lot of time. It’s almost every day, year-long. You can’t put your training ahead of that,” Marchessault said. “I decided I wanted to get out of that and back into racing. It feels good. It was the first test to see whether I could hold up two days in a row, and I did all right.”

Ask John Grenier about the hazards of juggling.

Grenier, owner of Rainbow Bicycle and Fitness and promoter of the criterium throughout its history, lined up with 37 pro men for Sunday’s 35-lap main event.

He pedaled eight circuits before coasting to a stop by the court house and reclaiming his post as coordinator and cheerleader.

“Not fast enough,” Grenier said. “I always try to race in a race I’m promoting, and it’s just so hard. It’s the stress. You think you’re OK. There’s so much adrenaline. You think you’re going to get started and be fine. Then we get about a quarter of the way into the race and I’m like, ‘uh-oh.'”

Ivy Luhrs of Minot admittedly questioned her ability to complete the women’s open race, but there was a weary sense of accomplishment in her eighth-place finish.

Luhrs, who also participated in Saturday’s road race, was most pleased that only four women in the field were fast enough to put her a lap down. A similar number dropped out entirely.

“It took my body a while to get going. I just wish I could’ve had a race like I had a couple years ago when I was a Category 4. I broke away from the breakaway and won the race,” Luhrs said. “I was just a little tired from yesterday. I had a lot of stuff going on in the winter, and I’m still catching up training-wise.”

Highly competitive in the 1980s, Luhrs put away her racing bikes for 18 years while attending to her parents and other obligations.

Her own health was the primary motivation for returning to the road in 2006.

“Life gets in the way,” Luhrs said. “I had gotten really overweight, and I said, ‘I don’t want to keep doing that anymore,’ so I came back and started racing again.”

Criterium racing is no Sunday joyride.

With the exception of the two or three riders successful at breaking away from the pack and the occasional straggler, tight packs of two dozen riders jockey for position around corners, up hills and through narrow straight-aways.

“I enjoy these fast courses. I’m not scared of the corners,” Marchessault said. “I love this kind of close, pack racing. It’s really like racing. You’ve got to pay attention every second.”

Marchessault initially took up the sport at age 30 because it gave him more consistent results and a greater sense of accomplishment than golf.

Bikes and the shops that sell them are in Poulin’s blood. He grew up in an Augusta family that owned a store before running Rainbow from 1987 to 1999.

Their start-and-stop stories are a far cry from the two principals in the Men’s Pro photo finish.

Nicholas Keough, the 20-year-old from Sandwich, Mass., who won by the diameter of a tire, is an up-and-comer on the national scene. Keough captured the victory with a slingshot move past Mark McCormack, 37, Grenier’s teammate and a multi-time U.S. champion.

“That was young legs against old legs,” Grenier said.

It was an out-of-place ending to a day that otherwise proved you’re never too old to get back on the bike.

Other division winners were Hank Pfeifle of Brunswick (Master 55+), Paul Magoon of Cornville (Category 5), Aaron and Melissa Ross of Norwood, Mass. (Category 4 and Women’s), Alex Dossin of Durango, Colo. (Category 3), Leo Devellian of Topsfield, Mass. (Master 45+) and Patrick Ruane of Webster, N.H. (Master 35+).

Three local men chased Magoon across the line in the Category 5 event. Christopher Darling of Lovell was fifth, John Cox of Hebron 10th and Neal Coughlin of Lewiston 11th.