It's possible to take up to a week off without losing any ground. In fact, a few days of rest may even improve your performance. But after a week of not training, you'll quickly start to lose your fitness -- a lot faster than it took you to build it up.
Cross-train Instead of Running
Cross-training is one way you can help maintain your fitness. Try activities that will not put added strain on your injury, and keep at them. Think of your time off as an opportunity to explore other activities. Biking and swimming are excellent aerobic exercises that keep you off your feet but still give you a good workout. Water running may be the best cross-training activity during an injury-related hiatus from running.
Even with cross training, you're bound to lose at least some fitness after a break from running, since you wont be working your main running muscles as hard as you would when running. A general rule of thumb is that it takes about two weeks of training to come back from every week of no exercise.
Ease Back into Running
Go easy when you first return to running because if you run too hard, you risk re-injuring yourself. If you've been out of your running shoes for only a week or two, start at about half the distance you were running before the injury. You should be able to build back to your former level in two to four weeks. If you've had a longer layoff, you need to be extremely conservative. You don't necessarily have to run slower -- just less. Sometimes jogging slowly might actually aggravate your injury, so it's better to run your normal pace and take walking breaks, when necessary.
As you build endurance, you'll be able to extend the amount of time that you run and reduce the walking time. In the beginning, take a day off after every running day. For your weekly mileage, you'll need to gradually work up to your previous level. If you were running 40 miles per week before your injury, stop at 20 or 25 miles for a couple of weeks, then build up to 30 or 35 miles per week before you hit the 40-mile mark again.
The silver lining of any injury is that you'll appreciate being healthy and running comfortably much more when you come back. But be realistic in your goals and expectations so that you don't get impatient and re-injure yourself. Improvements will come, but don't try to rush it. Taking a conservative approach to your training will help you stay healthy and injury-free.
Dealing With the Emotional Impact When you're recovering from a running injury, you become very aware of how running is a huge part of your life. Follow these tips to help you cope with the psychological strain of not being able to run.

