His mettle has been tested by three war wounds, a heart attack, a stroke and a broken hip.
Now, at 73, Lester Marks is testing himself again -- with a 3,400-mile bike ride.
He didn't own a bike seven years ago. Never exercised much either, he says.
Then, after a 1986 heart attack, heeding a doctor's advice, he bought a cheap bike and started riding to get the blood flowing and work up a sweat.
It became an addiction. The Joppatowne man, who rides 20 to 30 miles a day in warmer months and trains at the Holiday Spa the rest of the year, set out last week on a journey from Los Angeles to Boston.
The "Pedal for Power" trip is sponsored by the League of #F American Wheelmen, a national biking organization.
About 70 bicyclists taking part are expected to arrive in Boston July 3.
Mr. Marks says he has no doubts about whether he can complete the trip, even though his longest previous trek totaled only 100 miles.
"No ifs, ands or buts about it," he declares. "I will make it. Period."
This time, he'll be attempting 80 to 100 miles daily over 47 rigorously scheduled days and nights. Resting one day a week, the group will bike by day from hotel to hotel.
Mr. Marks says his legs, which still carry pieces of shrapnel from World War II and Korea, grew stronger almost immediately when he took up bicycling.
But his journey has not been without adversity.
A stroke six months ago almost kept him off the road. Three years ago, he fell from his bike trying to avoid a dog, breaking his hip. But shortly after surgery, he got back on the bike.
His latest trip carries a fee of $4,000, with part of the money going to the charity of each cyclist's choice. Mr. Marks plans to donate it to the League of American Wheelmen.
The retired military photographer stands in his home of 27 years where antique cameras line a wall. He casually mentions his injuries as minor setbacks.
"I get back on my feet a little quicker than most," he says. "I like a challenge.
"There are three people on the trip like me, in their late 60s and early 70s," he says. "We all can't wait to see that Grand Canyon."
On a bike.
Traveling in a car, he says, would be too much like speeding along watching a TV the size of a windshield.
He says he'll miss his cats, all four of them, and the neighbors.
But the road beckons with new faces, new places, new friends.
He'll savor it all -- slowly.
Unlike some younger, more competitive cyclists, he says he's in no rush.
"The young ones are hot rods that zoom off at 25 mph," he says. "Us old ones enjoy the country. The best way to see the country is at 15 mph."
He holds a T-shirt a friend made him. On the shirt, a smiling turtle on a bicycle crosses a finish line while a hare snoozes against a tree.
It's a fitting metaphor.
"I'm the little turtle," Lester Marks says. "I just plod along."