If you've read any fitness magazines or perused online workout videos recently, you've likely encountered the terms "dynamic warm-up" or "dynamic stretching." A dynamic warm-up is a method of stretching at the beginning of a workout that moves your body through various range of motion movements that are similar to a lighter version of your workout.
Research has shown that holding static stretches before your workout can actually lead to decreased muscle performance compared to dynamic stretching. For example, if you want to warm up your shoulders, you might do a series of big arm circles to the front and back. Additionally, rather than warming up your hamstrings by holding the common, touching-your-toes stretch, you would do low kicks to the front. Your muscles are being warmed up through controlled, fluid movements rather than holding a position for 15-20 seconds.
I'm including a sample dynamic warm-up below. I like to use this one regularly - it's easy to follow and hits most of the muscle groups that need to be warmed up.