EIGHTEEN years ago, Ronnie Guie considered buying a treadmill or a stair-climbing machine to stay in shape. Then one day on his lunch hour at Con Edison in Astoria, Queens, two co-workers invited Mr. Guie to take a walk to the top of the 10-floor building. He was breathing heavily by the time he got there, but was hooked: he had found his workout for free.

“For me, it’s a quick fix,” he said.

At 59, Mr. Guie says he still has the same waist size (30 inches) and weight range (150 to 155 pounds) that he did when he was 17, thanks to his five-day-a-week regimen. He climbs the concrete stairs usually 10 times or so in an hour, depending how much time he has. “I get the results out of it — and it’s not easy,” he said. “But I always feel great.”

Stairs are everywhere, of course, but they are rarely embraced as an option for getting into shape. They wait in the stale air wells of high-rises (especially in dense urban centers like New York City), or on stationary machines in the corners of health clubs now inundated by the more popular, but less strenuous, elliptical machines. Many stairwells aren’t even accessible, often because of post-9/11 security concerns. But when they are, or are opened especially for runners going up, they provide a workout that returns maximum value in minimum time, with low impact. And going up is much better for your knees than going down.

“Stair climbing will give you a little more bang for your buck because of the vertical component,” said Cedric Bryant, chief science officer for the American Council on Exercise. Compared to jogging or cycling at a moderate pace without much of an incline, stair climbing, Dr. Bryant said, “will be a bit more challenging and therefore allow you to burn more calories for that same amount of time.”