Though running isn't inherently harmful, it's smart to take precautions before you start something new. Alan Hreljac, Ph.D., of California State University in Sacramento, offers these tips:
* Increase time or distance -- not both -- no more than 10 percent from one week to the next.
* Stay on soft surfaces to lessen impact. Run on dirt paths, not streets.
* Stop before you get tired. When muscles fatigue, they don't absorb as much impact.
* Rest one to two days between runs. Injuries can occur when bone or tissue is continually taxed without time to rejuvenate.
* Strengthen. Stronger leg muscles absorb more impact. Try a lower-body move like squats.