Mechanics of Throwing

Figure 2: Firing Stage

Throwing

Throwing is a fairly natural activity for a person. Everyone at some point in time has thrown some object at a person. In baseball throwing becomes an art. Throwing a baseball is a relatively easy task, but throwing it accurately and with a high speed is difficult. People who play this sport spend a very long time perfecting their throw.

When one throws a baseball properly they are using there entire body to generate a large force to propel the baseball. A general throwing position starts with a person rotated 90 degrees from there target with there throwing arm 180 degrees from the target and parallel to the ground. The person then starts rotating their body back towards their target while there throwing arm starts bending until it is almost 90 degrees to their elbow, while the arm is bending at the elbow the throwing arm is rotating such that the arm rotates back almost 180 degrees from the target. Meanwhile the person is leaping forward with the leg that was initially pointed at the target while there other leg is planted into the ground. The person is bending at their waist and the other arm is rotating into their body. Around the point where the driving leg strikes the ground the throwing arm is rotating foreword at a tremendous angular speed and the person lets go of the ball. At the point where the ball is let go the persons body pulls the planted leg forward and the throwing arm finishes its motion towards the driving leg. The person is then generally square with the target. Figure 3 shows a pitcher throwing a baseball.

Figure 3: Picture of throwing motion

From figure 3 and the previous paragraph one can determine that it isn’t exactly easy to throw a ball properly. To be honest, it takes a lot of talent and hard work to achieve the perfection that major league players have. It is interesting to know that most major league pitchers arms are rotating around 90 to 100 mph during the firing stage.

So what just exactly is this torque coming from? It is coming from all of the forces in your body working together and acting on your arm. Even though most of the component forces come from many different parts of the body, they are all linked together in such a way they generate a large resultant force that pulls the arm back and then it rotates it foreword. It is helpful to visualize this like a whip. During the loading phase you are using your body to move the tip of the whip behind you and when you fire it the tip rotates forward at an extremely fast angular speed. The process of throwing acts very much the same way. During the loading phase of throwing your body is rotating your arm backwards using the combined forces from your body until the point where your arm stops rotating backwards and it starts rotating foreword at a very high speed from the torque. Part of the torque that rotates the arm forward comes from your arms resistance to rotating backwards. Try putting your forearm 90 degrees to the rest of your arm that is parallel to the ground, then try rotating it backwards. You should notice that the farther you rotate your armback the faster your arm wants to spring back.

One of the most interesting things about baseball is the motion of an actual baseball as it travels its path. This motion can be fairly unpredictable at times.

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