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The pushing and pulling action of the arms and shoulders refers to the individual movements that each arm and shoulder produce on the bat handle through their respective hands during the swing.
Since each hand grabs the bat handle from a different direction, the force from the respective arm and shoulder that it is generating on it will also be different. See Figure 4-28.
Let’s start by taking a look first at the player’s left arm during the swing. Since the left arm and shoulder are positioned in front of the left hand (Figure 4-29a) during the direction of the swing, or during the direction of the force (Figure 4-29b), then the left arm and shoulder will pull on the bat-handle throughout the swing (Figures 4-29c and 4-29d).
And if we take a look now at the player’s right arm during the swing, we see that his right arm and shoulder are positioned behind the right hand during the direction of the swing, or during the direction of the force (Figure 4-30a), and so the right arm and shoulder will push on the bat-handle as seen here throughout the swing (Figures 4-30b through 4-30d).
Okay, so now that we know for the right-hand batter that the left arm pulls on the bat handle and the right arm pushes on it, let’s define the muscles involved in both of these arms during this part of the swing, beginning with the left arm first.
If you recall during the loading phase back on page 9, Figure 2-10, the muscles on the back side of the left shoulder were stretched. Primarily, these were the Posterior Deltoid, Rhomboids and middle fibers of the Trapezius muscles. See Figure 4-31a. And with the left arm completely adducted across the front of the body seen in Figure 4-31b, two of the rotator cuff muscles were also be stretched in the back of the left shoulder which are the Teres Minor and Infraspinatus muscles.
These five muscles can be seen in more detail in Figure 4-32.
Now all five of these muscles contract during the launching phase and pull the left arm around bringing the bat-head in contact with the ball. See Figures 4-33a through 4-33d.
And before we go on to the muscles of the right arm, there is one more important muscle group I want to mention regarding the left arm and that is the elbow or forearm extensors. This muscle group doesn’t pull the arm around during the launching phase like the previous five muscles we discussed but rather, they help to extend the left elbow or forearm at contact. See Figure 4-34.
Specifically, the elbow extensors are the Triceps and Anconeus muscles, and these can be seen more specifically in Figure 4-35.
Okay, now let’s take a look at the player’s right arm. Again, going back to the loading phase on page 9, Figure 2-11, we found that when the right arm was abducted away from the body it stretched muscles acting around the right shoulder and chest. See Figure 4-36.
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