There are several things you can do to keep injury free if you're a runner:
Warming Up:
Take time to warm up for your fitness routine. Stretching is important, but many people try to stretch too quickly. When you stretch, slowly move into a stretch and hold it without bouncing. Be gentle. Your muscles elongate 10% from stretching and then another 10% during your work out. So let your body go through the transitions gradtually.
Slowly Increase your Workouts:
Keep a log of your workouts. If you increase your mileage more than 10% in any given week, you are doing too much. Remember that your muscles strengthen faster than your tendons and ligaments. So keep your workout increasing at a slow enough rate to let all body parts catch up.
Know When to Layoff:
When you feel that you’ve been working out a lot and you get that tinge of pain or uncomfort, take a day or two off. These signals are real signs that your body may be overworked, and it’s better to have a day or two of rest, rather than two to three weeks of nursing an injury and really missing out on your fitness workouts.