Among the bike racks and picnic tables at the Nickerson State Park water stop, a boy stands bearing a sign that reads "I'm 14 now because of you."

Most don't know his name and have never spoken to him. But every year since he was 3, cancer survivor Jack O'Riordan has taken his place by the side of the road with an updated sign. One glance is enough to forget your cramped calf muscles and push onward through the remaining hills.

On Aug. 4 and 5, one New Canaan resident and 12 Darien residents will embark on the 33rd annual Pan-Massachusetts Challenge, joining 5,500 other cyclists to raise a collective total of $36 million to support cancer treatment and research at Dana-Farber Cancer Institute through the Jimmy Fund.

The PMC raises more money for charity than any other single event in the nation. New Canaan resident Peter Reinemann attests to its singular nature.

"There are other races with similar causes and route distances, but the participants raise substantially less money," he said. This year will be his second time participating. He recalls that last year, "the Friday night before the race, they had Lance Armstrong speaking, and the following day he participated in the race. Sen. John Kerry also rode in it last year."

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Reinemann encourages newcomers to "just do it. You'll be very, very happy that you did."

Participants choose among routes ranging from 25 to 192 miles long, winding through 46 towns in the Cape Cod, Mass., area.

This August will be Darien resident Perry Boyle's seventh consecutive year riding in the PMC. He rode it for the first time in 2006 "just for the physical challenge," but claims that "once you ride it once, you're hooked for life."

Boyle rides with a group named Paul's Posse, named for Paul Schaye, a man he met at the PMC years ago, who later successfully battled GIST, a rare gastrointestinal cancer, now in his fourth year of remission. "Paul is doing well and will be with us this summer," he said. "We are hoping he can ride at least a part of the way."

This August, Boyle looks forward to the exuberant, positive atmosphere on the sidelines of the race. "One stretch in Cape Cod goes by (the Cape Cod Sea Camp) and there are 200 campers cheering us on with cowbells and horns. They even do the wave, and it's something we all look forward to in the race. It's known as `da hedge' because they stand on the other side of this 2-feet-tall hedge."

Past participants have posted videos of "da hedge" online, showing signs on the side of the road labeled "Da Hedge -- one mile" and the actual "hedge" itself, lined with kids eagerly reaching their hands out to high-five the cyclists, in full support of the cause.

The sideline audiences of the PMC are the cornerstones of the event, loyally standing in the same place each year so that they become living, breathing landmarks, reasons in the flesh that people come back year after year to ride.

Darien resident Terry Bock, readying for his sixth consecutive PMC ride this year, looks forward to the energetic crowds, but also related the sheer pleasure of riding toward the brilliance of an August sunrise.

"On the morning of the second day is a 15-mile stretch from Bourne Bridge to Sagamore Bridge in Bourne, Mass., with the sun coming up in the east, right in front of you as you're biking right along the Cape Cod Canal at 5:30 a.m. It is absolutely without question the highlight of the ride."

Martin Magida, also of Darien, will be participating for the third time this year. "We have a summer house in Cape Cod and the PMC goes by my road. On day two (of the race) I go to the end of my road and they come through. I'm just standing there eating my breakfast, mumbling to my wife, saying `I could do that,' and finally after eight years of that she said `I'm signing you up.' "

Three months after he registered for his first PMC, his mother was diagnosed with cancer and died.

"So I rode that first race for her," he said.

The camaraderie of thousands of individuals coming together for a single purpose, of belonging, for just two days, to a project of humanity where all ego is put aside, is invigorating.

Magida encourages everyone to think about participating, but he adds, "Be aware, it's addicting. I knew 25 minutes into my first race I'd be doing it again."

John Macfarlane, also of Darien, has ridden the PMC from 2002 to 2006 but will be returning this year for his son Jack's first time on the course. "I'm looking forward to spending time together before he heads off to business school," John said.

The father-son pair isn't a stranger to biking long distances. "Jack and I did the Face of America Challenge ride from the World Trade Center to the Pentagon in September 2002 (275 miles over three days) to commemorate those who died on 9/11."

Like many other PMC participants, the Macfarlanes ride with hope for the lives of loved ones. "We're riding for two friends currently fighting cancer, Caley Thomas and Holly Casey," John Macfarlane said.

Other Darien PMC riders include Asa Beach, Jason Chandler, Christopher Doherty, Charles Locke, Don McCarthy, James Palen, Thomas Ritchie and John Slonieski.