WHAT IS THE 10% RULE?
The 10-percent rule (10PR) is one of the most accepted and time-proven general principles in exercise science. It states that you should never increase your weekly mileage (or physical activity) by more than 10 percent over the previous week.
WHY IS IT IMPORTANT?
The 10PR gains its importance from the fact that the vast majority of running injuries are overuse injuries. They occur when you run too much or increase your weekly training program too quickly. Say you’ve been running 15 miles a week. For some reason—perhaps you want to prepare for an upcoming race or you just feel that you’re ready—you decide to pick up your training. Instead of running 5 miles three times a week, you manage to fit in five 5-milers. Your training increases from 15 miles a week to 25 miles a week—a 67 percent increase. This can lead to a greater risk of injury.
For runners, the biggest enemy is often their own energy and enthusiasm. You’re feeling great, so you figure that you can handle more training.
Our bodies need to adapt to the stresses that running imposes on them. This general adaptation simply takes time. As we GRADUALLY increase our mileage or intensity, our musculoskeletal system becomes stronger in order to support the rigors and impact of running. So be patient with yourself and build slow, it'll pay off in the long run!