Returning to running after a brief layoff? A general rule of thumb is that it takes about two weeks of “retraining” to come back from every week in which you do no exercise. Go easy on yourself during this period. Don’t let your ego convince you that you should immediately be able to run as you did before. If you’ve been off the roads 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.