Static stretching before a work out can be dangerous. It is important to warm your muscles up before stretching. Even the U.S. army revamped their physical training manuals and daily exercises to do light warm ups instead of stretching before a work out. Cool downs now consist of stretching to lengthen the muscles and tendons after the work out. This change was made in order to reduce the number of injuries sustained during physical training after careful study over many years. Science doesn't lie, whether or not you choose to accept is another story.
Interestingly, the science apparently says that you can't lengthen muscle and tendons and that stretching doesn't reduce injuries.