Most of the movements used to train explosive power have a distinct lower body bias. Sure, training the lower body to be more explosive will make you more athletic and teach you to recruit the muscles needed to power through a squat and sprint faster, but explosive upper body power is also important to being freakishly strong in the weight room.
The supine medicine ball reactive throw is an awesome tool to improve upper body power.
Supine Medicine Ball Reactive Throws
These throws train you to maintain a good position through a fast eccentric phase, and then explode through the concentric motion to finish strong. Try using these throws in a superset with the bench press and watch yourself power through the lockout.