Gretchen Reynolds, The New York Times:

Walk for two minutes. Repeat 15 times. Or walk for 10 minutes, thrice. The benefits for longevity appear to be almost exactly the same, according to an inspiring new study of physical activity patterns and life spans.

It finds that exercise does not have to be prolonged in order to be beneficial. It just has to be frequent.

Most of us who are interested in health know that federal exercise guidelines recommend we work out moderately for at least 30 minutes per day at least five times per week in order to reduce our risks of developing many diseases or dying prematurely.