Some are riding fast, featherweight 15-speed bikes and, on Day Five, will peel off from the 65-mile-a-day slowpokes to bike 100 miles in a day -- what cyclists call a "century."

For others -- huffing across 350 miles of Maryland, through Baltimore County horse country, up the steep hills around Frederick and past the Chesapeake Bay terrain of Charles County -- the seven-day odyssey probably feels like a century.

"I'm just hoping to get through the second day. I'll be thankful to get that far," said opera singer and Ellicott City resident Lynn Humphries-Russ, laughing. Humphries-Russ, 32, took up biking only a year ago.

Organizers of the non-competitive Cycle Across Maryland tour passing through Columbia this week signed up 900 people whose biking re'sume's, ages and professions vary wildly: There's a longshoreman, a letter carrier, a naval officer, an FBI agent, a pilot for the Trump Shuttle, a college professor, a custodian, a bartender and a sheriff.

The motivations of these cyclists, who were scheduled to reach Howard Community College yesterday, vary as well. Edward Fuchs, for instance, bikes to decompress from his job at Johns Hopkins Hospital, where he serves as outpatient HIV program coordinator.

"I've been doing this for the past three years, biking 10 miles a day, three times a week, just to keep my sanity," said Fuchs, a lifelong Howard County resident who lives in Ellicott City. Once he started to train for the race, he began biking more.

Fuchs said he spends half his time at work caring for patients infected with the AIDS virus and the rest of his time working to improve HIV patient services, treatment and research.

Fuchs views his participation in Cycle Across Maryland as more than a week-long way to blow off steam. He is dedicating his ride to the memory of a friend and mentor, B. Frank Polk, physician, epidemiologist and pioneer AIDS researcher at Johns Hopkins who died in October 1988 of a brain tumor.

"This is a bit of a personal journey," said Fuchs, a physician's assistant.

Fuchs likened the difficulty of the long bike trip to the challenge of his work with HIV patients.

"These distances are quite a jump up for me. I've never done anything like this before," said Fuchs, whose bicycling experience consists of doing 30 to 40 miles per day on weekends and less on weekdays. "I've particularly never done anything like this distance."

Polk, "a tremendous mentor" who helped Fuchs get involved in AIDS research, would have liked the idea of this trip, "which brings all Marylanders together," Fuchs said.

"Back in the '60s, Frank and his wife were very much into 'events,' " said Fuchs, "and this is a good example of one that brings people together. Frank would have approved."

Cycle Across Maryland, sponsored primarily by First National Bank of Maryland, is not intended specifically as a charitable event, although the organizers will make a cash contribution to the American Lung Association of Maryland.

This "Tour de Maryland" is meant more as a celebration and promotion of the diversity of the state.

The tour began in Havre de Grace, in Harford County, and has scheduled stops in Oregon Ridge Park in Baltimore County, Frederick, Columbia, Upper Marlboro, Waldorf and St. Mary's College.

The trip is modeled after an Iowa bike tour, sponsored by the Des Moines Register and known by its acronymn RAGBRAI (Register's Annual Great Bicycle Ride Across Iowa). The 495-mile RAGBRAI, now in its 18th year, was run last month. The three-year-old, 300-mile "Bike Virginia" was in June.

The Maryland cyclists pay a $110 fee, which includes camping space, shower facilities, first aid and daily transportation of cyclists' gear in a van called a "sag wagon," which will also transport tired cyclists. Cyclists also receive tour books, T-shirts and free entertainment at each site. Dinner and breakfast are provided to them along the way.

The cyclists are being entertained by marching bands, fire eaters and a country rock band, "Bird Dog and the Road Kings." They will be able to swim in a quarry, see the presidential "Air Force One," boat through Patuxent Park and tour historic Havre de Grace and the Merkle Wildlife Preserve.

But for most cyclists, the natural entertainment of Maryland scenery was the main attraction.

"It seems like a nice way to see the state," said Daniel O'Brien, of Ellicott City.

An assistant attorney general for the Maryland Department of Health and Mental Hygiene, O'Brien travels the state for his job to visit clinics and hospitals, but he usually views the scenery through the windshield of his car.

"I'm really looking forward to the part coming from Frederick into Columbia -- it's still a gorgeous area," said O'Brien, 38.

"I think the part around St. Mary's City will be pretty, too," he said, "more rolling than a lot of the Eastern Shore, but with a lot of water."

Fuchs, as well, is looking forward to the southern Maryland portion of the trip: "I like the idea of going through tobacco fields."

On the eve of the tour, several were worried about whether their training had been adequate.

"The recommendation is, you're supposed to have been regularly going 60 miles in a day in training; I've done that once this summer," said O'Brien, who worried that his younger brother Bill "is going to whip me bad."

Humphries-Russ, who is in a graduate program in opera performance at the University of Maryland College Park, was headed for a last minute checkup at a chiropractor's office.

She was a little worried about her bike, as well. She'll be riding a bicycle her husband won in an incentive contest at work -- a Huffy mountain bike, the squatty, rugged type designed to climb hills and rugged terrain.

"We've adjusted it, so it doesn't have those heavy tires" she said, "but there's nothing we can do about the handle bars," which stick straight out in a "T" shape, rather than curving down for a cyclist in a racing tuck.

Humphries-Russ has been training hard, logging 120 miles per week, trying to go 55 miles a shot occasionally, to improve her cardio-vascular capacity.

"I've seen how my heart goes; I did an audition recently for dinner theater and, wow, who needs aerobics?"

She has tried to persuade her busy husband to accompany her, but he didn't feel he'd had enough time to train, she said.

"I told him, 'Come on, if you can do 15 miles you can do 50,' " she said. "But he didn't buy it."