According to a recent study 100 steps per minute or 3,000 steps in 30 minutes constitutes a moderate intensity walk. National guidelines recommend all Americans should get “moderate physical activity" at least 2.5 hours a week for optimal health.

The researchers in the American Journal of Preventive Medicine have said, “This presents a challenge because health benefits are dependent on the intensity of activity, yet there are few valid and reliable monitoring tools available to the public that are affordable and easy to use.” 

The word moderate confused a lot of people. "Most people are familiar with the recommendation to get 30 minutes of exercise most days," said Dr. David Katz, director of the Prevention Research Center at Yale University School of Medicine. "Fewer people know that needs to be moderate intensity, and fewer still know what that means."

Simon J. Marshall, an assistant professor of exercise and nutritional sciences at San Diego State University and the study's lead author said, "Now we know what moderate is." He said people should use pedometers to find out if they are working out at the required intensity.

The researchers to quantify the recommendations of moderate exercise into achievable targets which could be easily measured by a pedometer undertook a study. Pedometers are successful at measuring the steps a person takes but cannot measure the intensity of the exercise. In the laboratory intensity is measured by determining how much oxygen taken in by the body during exercise, known as oxygen uptake.

The researchers enlisted 58 women and 39 men, with an average age of 32, to walk on treadmills while a machine measured their energy expenditure and monitored oxygen uptake. All of the participants wore pedometers during the exercise sessions and they completed four different 6-minute sessions on the treadmill at speeds ranging from 2.4 to 4.1 miles per hour.

They found that moderate exercise amounted to 92 to 102 steps a minute for men and 91 to 115 steps a minute for women. "It's a bit like a brisk walk," Marshall said. "If you can imagine you're late for a bus, you're in a hurry. It's not a leisurely stroll, it's a brisk walk."

"We believe that these data support a general recommendation of walking at more than 100 steps per minute on level terrain to meet the minimum of the moderate-intensity guideline,” Marshall said.

“Because health benefits can be achieved with bouts of exercise lasting at least 10 minutes, a useful starting point is to try and accumulate 1,000 steps in 10 minutes, before building up to 3,000 steps in 30 minutes,” he said. “Individuals can monitor their progress using a simple pedometer and a wristwatch.

The findings of the study, which was funded by the federal government, appear in the May issue of the American Journal of Preventive Medicine.