Are you getting enough exercise? from the May 2015 Harvard Women's Health Watch

Workouts that promise fitness with as little as four to seven minutes of high-intensity exercise a day are alluring. But can you really stay fit with such a small time commitment? "No," says Dr. Howard Knuttgen, research associate in physical medicine and rehabilitation at Harvard-affiliated Spaulding Rehabilitation Hospital, in the May 2015 Harvard Women's Health Watch.

Dr. Knuttgen has a file of articles and ads dating back to the 1960s promoting exercise regimens that offer to keep you fit with little investment of either time or effort. "This is exercise quackery. If a program sounds too good to be true, it probably is," he says.

Exercise is any activity that uses muscles to generate force. The more force exerted, the more exercise. In general, aerobic workouts (also called cardiovascular workouts) call for moving the body by walking, running, cycling, rowing, swimming, or another activity. Strength-building workouts involve moving an object like a weight or working against resistance.

It doesn't work to skimp on either intensity or amount of exercise. So how much aerobic activity is enough? Current guidelines suggest 150 minutes a week of "moderate aerobic exercise." But a brisk clip for some people can be a snail's pace for others. Using the talk test can help identify moderate activity: Not being able to carry on a conversation during the activity means it is strenuous. Being able to sing easily means it is too easy, and warrants stepping up the pace.

Strength training two to three times a week is also helpful. Always rest a day in between strength-training sessions.

Read the full-length article: "Are you getting enough exercise?"