Ten Percent Rule

A way to ensure that mileage gains are rapid and lasting. For most people, the expectation should be to increase distance and duration by about 10 percent per week. If you’re walking or running 10 miles this week (a good mileage to start), don’t do more than 11 miles next week, 12.1 miles the week after and so on. When you feel ready to increase the intensity / 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. The body doesn’t often like increasing volume and hard efforts at the same time.