Dynamic warmup exercises are better at preparing muscles for a workout than stretching cold muscles or plunging right into a workout, both which can lead to injury. A dynamic warmup involves moving the muscles gently to allow blood to flow to them, loosening them up so you can exercise them properly.
In this video, Point Performance’s medical personal trainer, Phil Silberman, demonstrates some examples of a dynamic warm-up that loosens all parts of the body. He begins by lifting the legs in a tall march to move the hip flexors and the legs. He then moves into a light jog to get the blood flowing, and some other variations such as jumping jacks and kicks. He also suggests doing some exercises without weights, such as lunges and squats. If warming up the upper body, do some arm circles to loosen the rotator cuffs and trunk rotations. There are lots of variations that can be done to warm up these muscles that can be fun and effective.