Last month I stressed the importance of footwork during the initial stages of the windmill pitch. To recap: Proper foot placement in the stance phase allows for good balance, which is critical to rhythm and coordination, and efficient force generation. The feet are the only body parts in contact with the ground, and the force produced as the feet push against the resistance of the ground are ultimately imparted to the ball.
To elaborate on how the forces flow from the ground to the ball, I will use the analogy of several cars in a train representing “segments” of the body (i.e. the foot, lower leg, thigh, etc.). If a force is imparted to a car at one end of the train, a chain of events will occur. Part of the initial force will in turn be imparted by the first car on the next car through their point of connection (i.e. a joint, such as the ankle, knee or hip). The orientation of the two cars relative to one another will determine what effect the force has on the second and each successive car of the train. Although this example is very simplified, it does reflects what happens in the body.
In pitching, the muscles of the leg contract in order for the foot to push against the ground. In reaction, the ground provides resistance and a push, equal and opposite, is imparted to the foot. Part of this force, plus additional forces due to motion of the foot, are then passed to the lower leg through the ankle joint. Likewise, force is passed from the lower leg to the thigh via the knee joint, from the thigh to the trunk via the hip joint, etc. This description is also oversimplified. The orientation and configuration of the muscles, tendons, ligaments and bones make this process extremely complex. Coordination of joint movements to ensure efficient transfer of force is very important.
Force production first comes into play at the end of the stance phase. As the pitcher’s center of gravity shifts from being centered over the back (stride) foot to being centered over the front (pivot) foot, the stride begins. The front foot then presses against the ground (and the ground pushes back with an equal and opposite reaction). This force acts to move the body forward through the stride. As the stride foot touches down it then assists the pivot foot in creating forces to close the hips and drive the body forward. Once the ball is released, hip rotation and the drive of the stride leg should cause the pivot leg to move forward, and the pivot foot steps up toward the stride foot. This step forward assists in dissipating the energy built up in the arm.
Principles of and flaws in the mechanics of the stride
Just as proper positioning of the feet is important during the stance, stride foot placement is also vital to pitching performance. For each athlete there is an optimal stride length depending on body height, leg length, flexibility, etc. Problems result in both underestimating and overestimating this optimal length. Understriding creates timing and force generation problems. A short stride does not afford the arm enough time to go through its motion, and lower body movements get ahead of upper body movements. If coordination between the lower and upper body is compromised, efficient flow of forces from the legs through the trunk to the arm is also compromised.
Overstriding causes a multitude of problems as well. Pitchers who overstride tend to land on a straight stride leg. A slightly bent knee is more advantageous because knee flexion can absorb some of the vertical force on the stride leg. Otherwise, this force could manifest itself in hip and/or low back injury. A stride that is too long also reduces the range of motion of the hips as they rotate from an open to a closed position. As the distance from the pivot foot to the stride foot increases, so does the stretch across the muscles at the front of the hips. Eventually the limits of these muscles’ lengths are reached and hip rotation is stopped short of full rotation. The longer the stride, the harder it is to close the hips.
A third problem that occurs in overstriding is movement of the center of gravity down and backward in relation to the stride foot. The longer the stride, the lower the center of gravity and the farther the distance from the center of gravity to the stride foot. If the goal of the movement is to move the body forward, the center of gravity should be high and forward in relation to the stride foot. “Sitting back” does not allow the body to assist the arm in propelling the ball forward.
Overstretching of the muscles of the stride leg also makes it difficult for the muscles to push against the ground. When a muscle is at maximal length it does not have good leverage, and can therefore create little force. All in all, overstriding minimizes the contribution of the lower body since hip rotation is hindered and force generation is minimized. This places the burden of force production on the throwing arm. Striding toward the target is the most efficient path.
Lateral position of the stride foot is also important. If we use a straight line from the center of the pivot foot to the apex of home plate as a guideline, placement of the stride foot too far to the left or right of this line will result in inefficient hip rotation. The farther to the left of the line the foot is placed (for a right-handed pitcher), the more closed the hips are at stride foot contact, thus reducing the potential for hip rotation during the delivery phase. Conversely, if the stride foot placement is too far to the right of the line, the hips tend to remain open and do not contribute to ball speed. Stride foot orientation follows the same logic. If the foot points toward first base, the lower leg and thigh will also rotate in that direction tending to close the hips prematurely. A stride foot pointing toward third base causes rotation in the opposite direction and makes it difficult to close the hips. Optimal orientation of the stride foot is half way between completely open and completely closed.
The legs act to generate force, rotate the trunk and absorb energy throughout the pitch. Considering these lower body contributions, it seems imperative for pitchers to strengthen the muscles of the feet, lower legs and thighs. The trunk (back and stomach muscles) needs to be strengthened as well since it is the link between the lower body and the arm. The shoulder, elbow and wrist joints cannot do it alone. Use of the legs in pitching is all-important.
|Sherry Werner: PhD is currently a biomechanics consultant with TMI Sports Medicine, and Tulane Institute of Sports Medicine, and a pitching instructor at the Sherry Werner Fastpitch Academy. She has held research positions at the United States Olympic Training Center. She received a MS degree in Biomechanics from Indiana University, and a PhD in Biomechanics from The Pennsylvania State University.
Dr. Werner's research has focused on the effects of throwing motions at the shoulder, elbow and wrist. Past projects include data collection and analysis of elite softball pitchers during the 1996 Olympic Games. Sherry also released an instructional pitching DVD with Jennie Finch in 2011.
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