Most sedentary people take only about 3,000 steps per day, says Bassett, and "they must make a concerted effort to get 10,000." These steps can be accumulated in formal exercise programs or through lifestyle activities such as climbing stairs or walking to do errands.

Lifestyle activities can provide health benefits similar to a traditional gym-based workout, according to a study performed at the Cooper Institute for Aerobics Research in Dallas. The study, called "Project Active," used the simplest kind of pedometer -- a step counter -- to record and motivate participants in the "lifestyle activity" group, says project director Andrea Dunn.

"People put them on first thing in the morning and take them off right before bed," Dunn says. "If it's mid-day and you only have 3,000 steps, you know you've got to get moving to reach your goal."

While 10,000 steps per day will meet most recommendations for adequate physical activity, Dunn says, it may be too high a number for some people and too low for others. "If you're only getting 2,000 steps a day it may be unrealistic to go immediately to 10,000," she says. "People who have a weight problem may need to target closer to 15,000 to 18,000 steps per day to lose or maintain weight loss."

"There's no magic number; it's all relative," concurs Abby King, associate professor of health research and policy at the Stanford University School of Medicine in Palo Alto, Calif. "If a frail older person who's been getting 2,000 steps goes up to 4,000 steps, that's a real success. The best thing for people to do is establish a baseline, then try to get more steps than they've been getting."