The more active you are, the greater ability you have to fight off illness, diseases and cancers. However, active lifestyles increase the odds that you may pull a muscle, or form a exercise related injury. Injuries can keep you off your feet for a few days up to a few weeks, depending on the extent of the ailment.If you're not regularly stretching before and after workouts, you could be at a higher risk for muscle cramps later on. Check out my post on dealing with muscle cramps as well. Here's the videojug library on preventing injuries. The site does a good job of covering everything from cramping, sports prevention massage, increasing your flexibility to warming up and cooling down techniques.