Static stretching involves slowly stretching a muscle to its end position and holding it for a short period of time, usually 10-30 seconds. This is the most common form of stretching and is often done to warm up for exercise -- but that is a big mistake!
Don't bend down and touch your toes to stretch your legs before running. Don't hold your hands together behind the back to stretch the chest before you bench press. Static stretching is not recommended for warming up. It can actually hurt your performance and make injury more likely if you do it right before exercise.
Why? Think of it this way: Rubber bands and muscles are similar in that they both have elastic properties. A rubber band that's too stretchy cannot be pulled back quickly enough to provide a strong "pop." Likewise, an overly elastic muscle has to work harder to generate the appropriate level of power. This can overtax and strain a muscle.
Most of the recent research suggests that static stretching right before playing a sport or exercising can impair performance, such as reducing jumping height, lowering muscular strength and power, and slowing sprint time.
Static stretching is not bad. As a matter of fact, it can be the safest and most effective form of stretching. It just simply should not be done as a warm-up.
Save static stretching for a cool-down activity, after you're done exercising, or as the main point of your workout (after you have warmed up). During this time, the muscles are warm, more elastic, and less likely to become injured.
Never statically stretch a cold muscle. Cold muscles are more likely to tear when stretched improperly. Be sure to warm-up with active, dynamic movement.