When beginning a running or walking program, people often want to know how to increase mileage (or exercise duration) quickly without getting injured. For most people, the expectation should be about 10 percent per week.

For example, if you’re walking or running 10 miles this week (a good mileage to start), don’t do more than 11 miles next week, 12 miles the week after, 13 miles the next week, 14.5 the next week, 16 the next, and so on. It doesn’t take long to get to a mileage that you feel comfortable sticking with.

When you feel ready to increase the intensity or duration of your workouts, you become more at risk for injury. If you’re planning on increasing your intensity during the week, you should back down your weekly mileage by 10 percent.

For example, if you’re doing 10 miles this week, but you want to add a more intense workout to your week next week, back your weekly mileage down to 9 miles to ensure you don’t put too much strain on your body. This allows your body to react to the stress of the added intensity without the added stress of increased mileage at the same time. This helps decrease your risk of injury and allows your body to more fully absorb the benefits of your intense workouts.

The 10 percent rule is designed to allow your body to adjust to this new stress. The body is incredible. It will adjust and respond very well to your exercise, but it can’t do it all at once. If you increase your mileage a little at a time the body will respond and become stronger more quickly.