Walking started as a fitness trend when ancient vertebrates first strode out of the primordial sea and onto dry land, 400 million years ago. Which makes walking a workout even older than yoga, though possibly not water aerobics.
And no wonder the sport has legs. It's the simplest, easiest and most accessible form of outdoor exercise -- or indoor, thanks to malls and skyways. It's low impact, requires no special location or equipment beyond decent shoes, and most people can do it. Its benefits, according to the Mayo Clinic, include lower blood pressure, decreased "bad" cholesterol and increased "good" cholesterol, reduced diabetes risk, mood and cognitive improvement and, of course, the ever-popular weight management.
Some people like walking but want to take it, well, a step further. Enter a couple of souped-up styles of perambulation: Nordic walking, which involves using specially designed poles; and race walking, which is walking really fast without breaking into a run.
Like regular walking, both can be practiced outdoors on trails and sidewalks, or indoors in an uncrowded space. But they require more attention to form -- newcomers can benefit from brief instruction -- and, in the case of Nordic walking, a bit more equipment.
Both are particularly popular among older people. They're rigorous but not risky, don't require club or team membership, can be done either alone or in groups.
Let's get one touchy issue out of the way: To the uninitiated observer, both activities can look a little, well, strange. Nordic walkers look like they meant to go skiing but forgot their skis. Race walkers adhere to a strict form that involves churning, bent arms, short strides and a bit of a hip-swivel.
"It's not a real glamorous thing," admitted medal-holding race walker Anita Macias-Howard, 57. "It's a funny-looking thing."
Most enthusiasts consider the occasional odd glance a small trade off for enjoyable activities that, they say, provide a great workout.
Nordic walking, popularized in Europe in the 1990s, is to walking as an elliptical trainer is to a treadmill -- arms move in rhythm with legs. The poles are used to push off, one side at a time, with each step. The extra effort increases the heart rate, oxygen consumption and calories burned, said Rhea Kontos, an instructor with Great Lakes Nordic Walkers. The upper body gets a toning, strengthening and range-of-motion workout that regular walking can't provide.
"With regular walking, you use 60 percent of your muscles -- with poles, 90 percent," Kontos said. "I like to say, if you pop in a stick of gum you'll have ramped it up to 100 percent, because you'll be moving your jaw."
Older people like using the poles, Kontos said, because it helps with stability and balance.
Connie Lewis started Nordic walking two years ago, often accompanied by friends on trails near her home in Plymouth, Minn.
"I like the added workout that you get," said Lewis, 63. "I have more energy and my arms feel more firm."