Q&A: Does an optimal walking speed require you to run?

In your story about home fitness tests, you give a rating of excellent to women who can walk a mile in 11 minutes, 40 seconds. But doesn't that pace, roughly 5 mph, require you to run? —K.P., Los Angeles

Not necessarily. According to our consultants, most people normally walk about 3 mph. The U.S. Surgeon General defines a brisk walk as 4 mph. And while it is hard to reach 5 mph without breaking into a jog, it is possible—if, as our test states, you're in excellent shape. Unfortunately, most people aren't. If you're out of shape, overweight, or older than 70, walking that fast can be especially difficult. For a more detailed analysis, you can try an online version of the Rockport walking test.