If you train in boxing or martial arts, you most likely call out numbered strikes when doing drills. It is sometimes difficult to tie the muscle movements with the numbers at high speeds, since it uses two separate parts of the brain. This drill improves the integration of the two parts of the brain. Knowing what your strike numbers are, have a friend stand close (four feet away or less) and throw shadow strikes at you lightly, but quickly. Call them off as fast as you can with the numbers you have tied to each strike. Calling the strikes recognition numbers off for reversed sides (from their position) also increases cross-side integration in the brain, making it easier to counter strikes from either side of the body.