Core 4 Stretch Video
Here's a quick three minute video provided by Stretch To Win Institute that teaches you how to stretch your Core 4 muscle groups. This includes your glutes, hip flexors, QLs (low back muscles), and Lats. This is an example of dynamic stretching which is now the preferred way to stretch over the old method of static stretching (holding a stretch for long durations).
Dynamic stretching is safe to do before or after exercise. An important key to remember is to keep your breath moving smoothly while stretching. It allows your body to release easier. Try it for yourself and see how great you feel!