Dan Hughes calls it the Lance Armstrong effect.

The influence of the American cyclist who defeated cancer and won the Tour de France seven times is one reason bicycling is popular, said Hughes, owner of Sunflower Outdoor & Bike Shop, 804 Mass.

“It ebbs and flows, but I think more and more people are riding bicycles than ever before,” he said.

The popularity of bicycle riding will be evident this weekend when more than 600 riders will roll into Lawrence for the 38th annual Octoginta. They will take part in Saturday’s individual time trials, a ride through the county and Sunday’s 80-mile ride through northeast Kansas. For those who prefer a shorter ride, there is an optional 40-mile route.

Participants come mostly from the Midwest. But this year more riders from other areas of the country are expected because Octoginta received publicity in a national bicycle magazine, said Craig Weinaug, vice president of the Lawrence Bicycle Club, which organizes the event.

“It’s people like me who just prefer to ride and bike instead of taking a car,” said Weinaug, who is also the county administrator.

The name Octoginta was derived from Latin and Italian words denoting an 80-mile cycling tour.

Activities begin with time trials at 7 a.m. Saturday. Bicyclists challenge the clock for a distance of 6.2 miles on a route that starts at old Kansas Highway 10 and Noria Road, just east of East Hills Business Park. A $20 entry fee is required except for riders between ages 10 and 18.

At 9:30 a.m. Saturday, the 30-mile Tour de County ride starts. The ride begins at South Park Recreation Center and winds through rural areas. The fee for riding is $5.

Anyone wanting to ride in Sunday’s 80- or 40-mile jaunts can pre-register Saturday from 8 a.m. to 7 p.m. at the South Park Recreation Center. Those rides begin at 8:30 a.m. at South Park. At the midway point the bicycle club will provide minestrone soup and sandwiches for lunch.

“That’s been part of the Octoginta tradition,” Weinaug said.

Lawrence police will provide escorts in the city, and the Douglas County Sheriff’s Office will patrol the routes.

Hundreds of riders will gather en masse near 11th and Massachusetts streets for Saturday’s Tour de County and Sunday’s longer signature rides.

“Usually we’re in the minority, but the bicycle will be the primary transportation on Massachusetts,” Weinaug said. “For those of us who like to ride, that’s kind of neat.”

In addition to the rides, a bicycle parts swap meet will be at 2 p.m. Saturday outside the South Park center. Antique bicycle displays will also be set up. Lawrence firefighter James McKenzie will demonstrate how to ride old bicycles with big front wheels. Lawrence dentist Mike McBride will have his bike collection on display.

Riders in Octoginta range from ages 11 to 70-plus, Weinaug said.

Bicycling is popular with older adults for reasons beyond Lance Armstrong, Hughes said.

“A significant part of the population that’s aging are finding they can’t do the high-impact activities like jogging that they used to do, so they are turning to bicycling,” he said.