Running a half-marathon is easy, Bob Gralley, 87, said:

"I put one leg in front of the other."

For 13.1 miles.

That Gralley can do this at his age is remarkable. Yet on Saturday, there he'll be at the 13th Baltimore Running Festival, a silver-haired methuselah plugging along beside others young enough to be his great-grandchildren.

Not that they'd know it. Trim and limber, Gralley doesn't look his age, though race officials said the Parkville resident is the oldest participant entered in any of the day's events.

"I don't bring it up during races," Gralley said. "I don't jump up and down and say, 'Hey, hey hey! I'm 87!' But my son Craig, who runs with me, gets a kick out of pointing to me and saying, 'Here he is, the oldest runner!'

"I get a little embarrassed but ... I don't tell him not to do it."

Craig Gralley, 58, will stick close to his father Saturday. They've run more than two dozen marathons together and the son said they use the time "to reconnect."

"I'll ask Dad's advice on things. It's pure gold to run with him," said Craig Gralley, a retired CIA analyst from Great Falls, Va. "He's slowing down a bit but he still tells me that he's going to drag me over the finish line, like he did in our first marathon in 1982."

For the 2006 Baltimore Marathon, Craig Gralley wore a T-shirt that read, "I'm running with the old guy." His father's chest read, "I'm the old guy."

He was only 80 then.

This won't be his last race, if Gralley has a say. To date, he has completed 42 marathons and 13 half-marathons since he started jogging in 1972. Five times he has run the Baltimore Marathon, most recently in 2008 at age 82. Gralley's time that day (5 hours, 55 minutes and 20 seconds) paled alongside his personal best (3:04.28) in both the 1981 New York and Boston marathons.

"For some strange reason, I've found that the older you get, the slower you get," he said.

But the urge to run stays strong.

"I look forward to getting up in the morning, stretching for 15 minutes and jogging [at 8 a.m.]," he said. "I'll do it as long as I enjoy it. I'll be 88 in January, but my real objective is to run a marathon when I'm 90."

That thought worries his wife of 64 years.

"Twenty-six miles is too much for a 90-year-old man," Betty Gralley said.

"But you wouldn't divorce me if I did it," he said.

No, she said, "but I'd try to discourage it."

Gralley wisely left it at that.