Dynamic stretching involves movement and action, as opposed to static stretching where you hold a specific pose. I generally do both types of stretches to warm-up and especially attend to the muscles that I plan to focus on during my workout. For example, prior to doing a routine that focuses on legs, I would do lunges (dynamic) as well as quad (static) stretches. Movement not only warms up and increases the flexibility of your muscles but also causes your heart rate to slowly rise, as opposed to a sudden jump if you go from static stretches to cardio.
If you’re planning on doing more of a cardio workout then the key is to slowly get your blood pumping. It’s best to do this while stretching out all of your major muscle groups and focusing on any smaller muscles that you find sensitive. For example, I’ll start a yoga routine with several sun salutations, during which I’ll hold plank before flowing through the rest of the vinyasa, and also bend one knee at a time in downward dog to stretch the opposite calf. The motions of the vinyasa are considered dynamic stretching, while holding plank or a calf stretch are static.
There’s also a third type of stretching – ballistic stretching, where you bounce around a bit in order to loosen up your muscles. While doing this type of stretch, I always think of swimmers jumping around to loosen up their shoulders prior to a race. There are many contradictive sources when it comes to this kind of warm-up. On one hand, ballistic stretches can increase your range of motion and promote greater flexibility than static or dynamic stretches alone. On the other hand, jerky, bouncy movements can severely injure you, especially if you’re not completely relaxed while doing them. I like to include ballistic stretches in the middle of a routine if I’m about to switch over to focus on a new muscle group. To each their own!
Some form of warming up is critical to getting your body ready for a work out. This is especially true if you just woke up or were sitting still all day because it reduces your risk of injury; cold, inflexible muscles make you more injury prone. Similarly, your body benefits from a cool-down stretch before you go back to sitting around or whatever. So take the extra few minutes and take care of your body.