Preseason conditioning is important in preventing sports injuries. It takes at least two weeks to get in minimal shape to play a recreational sport and two to four weeks for an athlete to get in shape for a sport in which they do not normally participate. For someone who has been inactive, it takes about a month for every year you have been away from a sport to approach the same competency you had at your peak. Experts warn that the less fit you are, the more likely you are to be injured when you start a vigorous sport or exercise.
A conditioning regimen should include aerobic exercise, walking, cycling or jogging, for 30 minutes, four times a week. Also include 15 to 20 minutes of weight training twice a week. Another important part of a conditioning regimen is warm-ups and stretching, both before and after exercising. The warm-up is the step people in recreational sports most often forget. While exercise experts have different opinions about the types of stretches to use, most say static stretching, where you lean slowly into a stretch and hold for 10 to 15 seconds, is best.
-- Ellen Creager "Warm-weather warm-up: Time to get ready for spring sports" The Seattle Times, April 30, 2000, L3