Unless you’ve been living in the baseball equivalent of a Himalayan monastery, you’ve heard pitching and hitting coaches avowing the importance of “hip-to-shoulder separation.” I’m not exactly sure when it began, but sometime in the last several years, someone coined the term, and it spread like wildfire. According to advocates of this tenet, pitchers and hitters should rotate the pelvis while the torso remains closed for as long as possible. The resultant diagonal stretch through the trunk allows the athlete to take advantage of the elastic properties of the abdominals, and chest muscles to store and then unload energy to be transferred from the lower half to the arm or bat.