Last year alone, fitness walking drew 6.3 million new participants, says Mary Gregory, marketing manager of The Walking Magazine, a Boston-based publication that debuted four years ago and now claims a readership of 2.4 million. "The average age of fitness walkers is 43, and 65% are female," Gregory says. Fitness walking is defined by many exercise experts as walking at least three times a week for at least half an hour at a brisk pace, says Brad Ketchum Jr., the magazine's editor. A brisk pace is defined as walking at a 12- to 15-minute-mile speed or about 4-5 miles per hour. Swinging the arms a bit as you walk is a good idea, because it increases your heart rate and burns more calories. In race walking, an even speedier form of fitness walking, exercisers help propel themselves by exaggerated hip and arm swings.

Distinguishing between health benefits and fitness benefits is a concept new even to exercise experts, says John Duncan, a physiologist at the Institute for Aerobics Research in Dallas. A major health benefit of exercise is improved cardiovascular functioning, while a fitness benefit is improved endurance. Recent studies suggest that people who exercise even at low intensity can achieve health benefits, along with some degree of fitness, defined by exercise experts as the ability of the body to transport and use oxygen. To become super-fit, though, exercisers must increase their workout intensity, and thus they improve their endurance and athletic performance. But experts say most people are more interested in the health benefits of exercise than the fitness benefits. If so, they can jog at a 10-minute-mile pace or walk an equal distance, says Dr. Neil Gordon, director of exercise physiology at the Institute for Aerobics Research. "You get the same health benefits. What counts (for improving your health) is the energy expended, not how intensely you exercise."

Learning-or relearning-to walk correctly is the key to injury prevention and enhanced enjoyment of walking for health, says Corey Dzitzer, a Santa Monica kinesiologist who teaches people how to walk in three-hour workshops. "People tend to lock their torso, pelvis or head when they walk," says Dzitzer. All are don'ts in her book. "Good posture and relaxation are important when walking for exercise," she says. "Allow the torso to swing with the arms. Military-style walking is not correct. Exercise walking should be free flowing. Land lightly on the heel. Roll from the heel to the toe." Before walking, Dzitzer says, do leg and spine stretches; she warns people to cool down after a walk with some stretches then as well.