Picking up where we left off in the last section (Part 2 of 12), where the shoulders and arms were moving backward, we also have at the same time muscles contracting along the spine to help turn and rotate it, which includes the chest, abdomen and upper body, in the same direction. See Figures 2-14a through 2-14c.
Let’s look at this from behind home plate. Starting in this stance position (Figure 2-15a) where only the back (right) shoulder is visible, as he prepares to swing we can start to see the chest, abdomen and upper body turning away from the pitcher (Figure 2-15b) to the point where both shoulders become more visible (Figure 2-15c).
This action of the abdomen, chest and upper body all turning away from the pitcher and toward the catcher gives the appearance that the shoulders are rotating backward with them when in effect, it is the spine that is rotating carrying the shoulders with it.
This backward rotation of the spine is caused by the contraction of the Lateral Spine Rotators which is a general name for the muscles that cause spine rotation. Their individual names are External Abdominal Oblique, Rotatores Spinae and Multifidus Spinae. See Figure 2-16.
Now, to get the body to rotate back and away from the pitcher for our right-handed batter, the Lateral Spine Rotators on the left side of the body needs to contract. In doing so the upper body is turned to the side opposite to that from which these muscles act. See Figure 2-17.
This may be opposite of what you think however, this has to do with the upward and oblique orientation of these muscles in the spine. To help you get a clearer picture of how these muscles are acting, just think about the movement that takes place when you do oblique sit up crunches.
In Figure 2-18 shown below, the athlete has already performed a sit-up and has rotated his chest, abdomen and upper body to his right. However, it is the Lateral Spine Rotators on the left side of his body that are doing the contracting here which is also in the same direction for our right-handed player shown above in Figure 2-17.
And if you have ever performed these sit-ups before, then you are already aware of where the muscle contractions are taking place. Again, contraction of the Lateral Spine Rotators on the left side of the body turns the front of your body to the right as seen above in Figure 2-18, and the opposite is true for the Lateral Spine Rotators on the right side of the body which turns the front of your body to the left as seen below in Figure 2-19.
Okay, so hopefully you have a better understanding of how these muscles are acting because as the contraction takes place in the Lateral Spine Rotators on the left side of the body, as seen below in Figures 2-20a through 2-20d for the right-handed batter, the exact same muscles on the opposite side of the body are getting stretched, which are the Lateral Spine Rotators on the right side. These Lateral Spine Rotators on the right side are now ready to contract in the launching phase of the baseball swing because they are now fully stretched or loaded. These muscles, along with those in the hips, provide the necessary movements in the body that produce a rotational hitting technique.
In the next section we will discuss the third noticeable movement during the loading phase which is, the beginning of the timing step, and identify the muscles involved with it.