Bill Cotton biked to our appointment, of course, from his home in Cheltenham to Lloyd Hall on Kelly Drive. Because he was a little early, he decided to kill time. So he biked the eight-mile river-drive loop.

By the time I arrived, the sun was higher, the temperature was climbing into the 90s, and Bill had already logged 19 miles and was glistening like an oiled bodybuilder.

Bothered by the heat? No way. He mounted his trusty Cannondale 21-speed and rode the loop again with me, cruising at 13 m.p.h. effortlessly.

His customary road-biking speed is 11 m.p.h. At that rate, he can spin the sprockets forever, he says.

Last year, to celebrate his 69th birthday and the approaching summer solstice, he biked to Cape May and back - 227 miles in 22 hours.

This year, to mark his 70th, he had something much more ambitious in mind: a bike trip across the United States. Bill, a retired machinist who worked at the Frankford Arsenal, Pennwalt and the U.S. Mint, posted his plans on his Web site. That's where his beloved wife, Margaret, learned about them.

"What's this I see about you going cross-country?" she asked Bill one day. "That some kind of pipe dream?"

"Well, no," Bill said. "You wanted a new house, and we got a new house. I want to do this. That's the deal."

Actually, it wasn't the deal. At least as far as Margaret was concerned. She put her foot down, and Bill pared down his itinerary.

His idea of something more modest? He biked from Cheltenham to Ocean City, Md., riding straight through the night (and a lot of rain). Then, without a moment's shut-eye, he turned around and pedaled home. Total time: 40 hours, 19 minutes. Total mileage: 340.

He plotted his route with the help of a favorite tool: a global positioning device about the size of a cell phone that snaps on his handlebars. The only untoward incident: With about 20 miles to go, Bill bonked - ran out of steam. Luckily, there was a Dunkin' Donuts nearby. He gobbled an apple fritter, and that sugar surge powered him home.

"Some folks might think this is a weird way to celebrate your birthday," I suggested. "Some people might think you're crazy."

"I am crazy!" Bill exclaimed. "Crazy about my health!"

Growing up in St. Petersburg, Fla., Bill was like most kids - he biked everywhere all the time. When he moved to Philadelphia at 17, he put childish things, like bikes, behind him.

When he was 35, Bill decided to buy a bike for his older daughter, then 11. Naturally, once he'd assembled it, he had to try it out. Whee! He'd forgotten how much fun it was. He decided to ride the bike to work, from his home in West Oak Lane to North Philly. The trip was about five miles. He arrived exhausted - and exhilarated.

So he bought a bike for himself, one for his other daughter, and biking soon became the family's favorite form of weekend recreation.

It wasn't enough. When he was 40, Bill's waistline began to balloon. He was working as a manager at night, taking courses at Temple during the day. Too much sitting, not enough moving. His weight hit 220; he felt and looked like a blimp.

One night, the company nurse invited him to have his blood pressure tested. The reading was off the charts. She urged him to see a doctor. His advice: Take meds to lower your blood pressure pronto.

Bill didn't cotton to polluting his body with drugs. So he proposed an alternative: He would ride his bike regularly, not just around the block, but far and long enough to really tax his heart and make his blood pipes more open and flexible.

It worked. Over time, the pounds began dropping (he weighs a lean 186 today), and his blood pressure fell to within the desirable range. He began making regular forays up Routes 309 and 611 to places like Lansdale and Doylestown. He rode the bike path to Valley Forge and beyond. He hooked up with fellow cycling enthusiasts and joined several clubs, sometimes planning and leading rides. He took bike trips to Wellesley, Mass., and Williamsburg, Va.

"I love being outside, seeing new places, discovering new things," Bill said. A proud member of the Bicycle Club of Philadelphia, he also loves to describe his bike trips, to map out rides, and to supply directions (also known as "cue sheets") and "topos" (topographical charts) to other long-distance cyclists.

Lately, Bill's cholesterol numbers have been rising. ("I hate to admit that age makes a difference," he said.) About four years ago, his wife went to summer fitness camp and came home a vegan. Now, Bill follows the diet (no meat, fish, eggs or dairy products), at least when he's at home.

"My barbecue ribs are the best in the world, but I don't cook them anymore," he said wistfully. Instead, he satisfies his palate with cheesecake and bread pudding made from tofu.

Bill rides about 100 miles a week, mostly on weekends. Weekdays, he works on his speed, doing laps on a three-mile loop in Cheltenham. Whenever his lipid numbers are too high, he pursues his own cardio-therapy. He saddles up his bike and goes long. "I hate to have to rely on medicine," he said.

By the way, Margaret, once you get settled in the new house, Bill still plans to bike across the United States.