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Training the baseball hitter: what does research say? Guided too long by folklore, baseball batting has become a science.
JOPERD--The Journal of Physical Education, Recreation & Dance March , 2005
Former baseball star Jim Lefebvre (1983) claimed that hitting a baseball may be the most talked about but least understood skill in all of sports. Historically, hitting instruction has been based on intuitive thinking by "hitting gurus," rather than on scientific fact, which has contributed to this lack of understanding (DeRenne, Stellar, & Blitzbau, 1993). Compared to other sports, baseball has lagged in regard to the application of science to the development of the swing and training methodology.
Although athletes and coaches have many hitting drills to choose from, few of these drills are grounded in science. A thorough understanding of the mechanics of the baseball swing is critical to formulating a sound training methodology. Therefore, the purpose of this article is to use previous studies to describe proper swing mechanics and to provide a few examples of drills that could be used to train these mechanics. However, the concepts of bat velocity and bat quickness must be considered before any discussion of swing mechanics. Recognizing the difference between these two, often misunderstood, concepts is a prerequisite for understanding the mechanics of the baseball swing.
[FIGURE 1 OMITTED]
Bat Velocity and Bat Quickness
Bat velocity is the speed at which the bat head is traveling at the moment of contact (Stellar, House, DeRenne, & Blitzblau, 1993). Bat velocity is important for several reasons. According to the equation, force equals mass times acceleration, the greater the velocity of the bat at contact, the greater the force that can be imparted to the ball and the farther the ball will travel once it is hit (Hamilton & Luttgens, 2002). In addition, if energy equals one-half mass times velocity squared, a bat swung with more velocity will result in greater energy imparted to the ball. In short, the higher the velocity of the bat at contact, the higher the velocity of the batted ball (Adair, 1990). This is true both for wooden bats and aluminum bats (Crisco, Greenwald, Blume, & Penna, 2002).
Bat quickness is the time it takes to move the bat head from the launch position to contact with the ball, measured in seconds (Hay, 1993). The relationship between bat velocity and bat quickness is usually inverse in effect (Stellar et al., 1993). That is, players who exhibit high bat velocities tend to have poor bat quickness (high swing times). The bat quickness of major league hitters has been calculated to be 0.14 to 0.15 of a second in contact hitters, and 0.17 to 0.18 in power hitters, demonstrating the inverse relationship between the two performance variables (Stellar et al., 1993). This relationship has been attributed to changes in decision time (Hay, 1993). Decision time is the amount of time the hitter has to read the pitch and decide if, when, and where to swing the bat. As bat quickness improves, decision time increases, and the chance of making a correct decision increases.
Variation in swing mechanics can account for much of the observed relationship between bat velocity and bat quickness. For example, as bat wrap increases, bat velocity increases, but bat quickness becomes slower. Bat wrap refers to the degree to which the bat points toward the pitcher in the launch position (figure 1). The greater the wrap, the farther the barrel of the bat must travel to get to the contact zone. The greater distance traveled results in higher swing times (slower bat quickness), but the additional time allows the hitter to generate more bat velocity. Varying the extension of the lead elbow has a similar effect. In other words, as extension increases, so does the length of this segment as a lever. The end result is a wider radius from launch to contact and a subsequent increase in angular velocity and swing time (Bunn, 1965).
[FIGURE 2 OMITTED]
It is important to realize that high bat velocity does not necessarily mean a more productive hitter. This can be confirmed by the lower batting averages typically observed in power hitters. Similarly, great bat quickness with poor bat velocity will most likely result in poor power statistics such as extra base hits and slugging percentage. A hitter must combine bat velocity and bat quickness in order to maximize productivity. Players who have great bat velocity and outstanding bat quickness hit for both power and a high average. These players are the superstars of the game. There are, of course, other factors that play a role in hitting productivity. These include, but are not limited to, visual skills, pitch selection, and confidence. Due to the limited scope of this article, these factors will not be discussed.
Improving bat velocity without compromising bat quickness can be accomplished with strength and power training. That is, the associated musculature is trained to contract more forcefully and rapidly without any changes in swing mechanics (i.e., increased bat wrap). Using electromyography, Shaffer, Jobe, Pink, and Perry (1993) explored the muscle activation patterns of various muscles during the baseball swing in professional baseball players. The authors concluded that hitters should emphasize the abdominals and muscles of the lower back due to the high muscle activity observed in these muscle groups throughout the swing.
Although most abdominal and lower back exercise would benefit the hitter, those exercises that involve twisting of the torso are more specific to the movement patterns of the baseball swing (Garhammer, 1983). Once a base level of local muscle strength and endurance has been established via various crunches and lower back exercises, hitters can begin to incorporate resistance with rotation. An example of such a drill is the hitter's toss, a rotational plyometric exercise depicted in figure 2. In this drill, the hitter loads the muscles of the trunk and then throws the medicine ball as forcefully as possible while mimicking the mechanics of the swing as best as possible. Theoretically, if the ability of the musculature to contract rapidly increases, and swing mechanics remain unchanged, both bat velocity and bat quickness could be improved concurrently.
Baseball Swing Mechanics
In order to simplify data analysis, the study by Shaffer et al. (1993) divided the swing into four separate phases: the wind-up, pre-swing, swing, and follow-through. Because of its effect on these four phases, the hitter's stance before initiating the swing will also be discussed.
Stance
The manner in which a hitter stands in the batters' box before the pitch is a subject that lacks scientific evidence (Hay, 1993). Although hitters' stances are individualized, it should be noted that most major league hitters have certain characteristics in common. Identifying these characteristics is important because problems with the stance can lead to problems with the swing.
The first characteristic of the major league stance is dynamic balance. This means that the head is over the center of gravity and the center of gravity is equidistant between the balls of the feet. If the hitter is unbalanced, the hitter will not be able to create a base of support to execute the proper swing mechanics (DeRenne et al., 1993).
The second characteristic of the major league stance involves the position of the head. The head should be facing the pitcher in such a way that the batter can see the pitcher with both eyes. In addition, there should be minimal tilt of the head so that eyes are parallel with the ground. Starting with the head in this position will help to keep the distance between the chin and the lead shoulder relatively constant throughout the swing (DeRenne et al., 1993).
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
The third characteristic is rhythm. Most major league hitters incorporate rhythm while waiting for the pitch in their stance (Hudgens, 1997). Rhythm keeps the body free of tension and aids in the timing of the pitch. The hitter's rhythm starts with large movements and slows down to a smaller movement just before the swing. Most successful major league hitters slow down their movement or rhythm just before they stride. Videotape and mirrors are useful tools for improving the stance. Hitters may think they are incorporating balance, proper head position, and rhythm in their stance, but on seeing their stance in a practice or game situation, they may be surprised to observe otherwise.
Wind-up Phase
The wind-up phase begins as the lead foot leaves the ground and ends when it returns back to the ground (figure 3). This phase may also be thought of as the stride. The stride is a step taken by the hitter in the direction of the pitcher (Bennett & Yeager, 2002). The stride is a preparatory movement that allows the hitter to generate linear momentum in the direction of the pitch. This momentum is desirable unless the hitter is unable to maintain balance (DeRenne et al., 1993). As the stride takes place, the hands, shoulders, and hips also move. The hands move back toward the rear shoulder until they are located over or behind the rear foot, and the shoulders and hips rotate inward (Welch, Banks, Cook, & Draovitch, 1995).
[FIGURE 5 OMITTED]
The stride must be completed before any other forward movement is made in the swing. In other words, rotation of the torso toward the pitched ball should not take place until the stride heel makes contact with the ground (DeRenne et al., 1993). The baseball swing is initiated, not by the back leg as many coaches teach, but by the front heel making contact with the ground (Welch et al., 1995). No further linear movement of the body should occur once the stride heel lands. If the lead foot is not down before the pitched ball is half way to home plate, the hitter will not have enough time to rotate the trunk, shoulders, and bat into contact with the ball.
The length of the hitter's stride also affects his or her reaction time. Stride length is directly proportional to linear body movement, therefore a longer stride will move the head and eyes that much closer to the pitched ball. For example, if an 85 miles-per-hour pitch is thrown to a hitter with a five-inch stride, the same pitch will have an effective speed of 88.5 miles-per-hour to a hitter with a 15-inch stride. A short stride also increases the chance of the stride being consistent every pitch (Hay, 1993).
The "command soft-toss drill" is an effective means for teaching the stride (figure 4). During the soft toss, the coach provides a verbal cue of when to stride. Once the stride is down, the coach waits and then tosses the ball so that the hitter can hit it into a net. The objective of the drill is to separate the stride from the swing, which teaches the hitter to stop the linear movement once the stride foot has made contact with the ground. This drill also emphasizes the importance of an early stride (timing) and allows the coach to provide feedback in regard to the length and direction of the stride.
[FIGURE 6 OMITTED]
Before ending this discussion of the stride, the concept of inward turn must be addressed. Ted Williams (1971) called the inward turn a "hip cock" and compared it to a pendulum. It is a movement of the hips during the stride so that the hitter can countermove them more efficiently during the swing. Scientific research supports Williams' intuitive reasoning. Welch et al. (1995) reported that hitters rotated their upper bodies in the opposite direction of the swing starting with the arms and shoulders, followed by the hips.
There is a difference of opinion as to when the inward turn takes place. One study reported that the inward turn occurs while the hitter is shifting his or her weight against the rear leg before the stride (Welch et al., 1995). Other sources suggest that the inward turn reaches its maximum during the stride (Hay, 1993; Swimley, 1964; Williams, 1971). Regardless of when the inward turn occurs, its importance is obvious in regard to the generation of bat velocity. It should also be noted that too much inward turn may make it impossible to keep both eyes forward, and therefore it may be detrimental to hitting performance.
An example of a drill designed to emphasize the inward turn is the "load drill" (figure 5). With a ball placed on a tee, the hitter starts the drill in the contact position. From here, the hitter recoils backwards under control. After achieving some degree of inward turn, the hitter then proceeds with striking the ball. The objective of this drill is to perform the inward turn while focusing on swing rhythm and swing cadence. Additionally, the coach can provide feedback as to whether there is enough, or too much, inward turn.
[FIGURE 7 OMITTED]
Pre-Swing Phase
The pre-swing phase is very short. It begins when the lead foot reestablishes contact with the ground, and it ends when the actual swing begins (figure 6). During the pre-swing phase, the hands, shoulders, and hips eventually stop moving. Once this occurs, the hitter has reached the launch position. From the launch position, the hitter then decides whether or not to swing at the pitch. The launch position of the hands is located near the back shoulder, with the hands over or behind the rear foot (Hudgens, 1997). The rear elbow should move upward when the hands reach this position (DeRenne et al., 1993). The hands have not initiated any forward movement up to this point (Bennett & Yeager, 2000).
Generally speaking, power hitters have more bat wrap than contact hitters in the launch position (Stellar et al., 1993). Virtually all players, including contact hitters, have some degree of bat wrap. Without bat wrap, the wrists will not be abducted (radially deviated) before the swing phase. Adduction of the abducted wrists is the last event to occur in the swing sequence.
As with the stance, the use of videotape can help the hitter achieve the proper launch position. The use of videotape in this instance can be an invaluable tool to the young hitter.
Swing Phase
The swing phase can be partitioned into three sub-phases; early, mid, and late (Schaffer et al., 1993). The early swing phase begins when the pelvis begins to uncoil and ends when the barrel of the bat is perpendicular with the ground (figure 7). As the hips uncoil, the shoulders continue to coil in the opposite direction. This counter-rotation of the shoulders stretches the trunk muscles. This stretch enhances the ability of the musculature to contract and puts the torso in a position in which it can unwind powerfully (Garhammer, 1983). Toward the end of the early swing phase, the shoulders will begin to rotate in the same direction as the hips, bringing the bat forward toward the pitch.
Torso flexibility is clearly important in order for the hitter to achieve counter-rotation of the shoulders as the hips begin to uncoil. If the torso is inflexible, the shoulders will rotate prematurely as the hips begin to uncoil, disrupting the hitter's timing. Torso twists performed with the bat as well as static stretching with a partner are examples of appropriate hitter-specific drills to improve torso flexibility.
[FIGURE 8 OMITTED]
The mid-swing phase begins when the bat is perpendicular to the ground and ends when the bat is parallel to the ground (figure 8). "Bat lag" is the term used to describe the position of the bat as parallel to the ground (DeRenne et al., 1993). The shoulders continue to rotate toward the pitch, taking the arms and the bat with them. As the bat moves forward, the barrel will drop automatically into bat lag. The bat lag position is important in regard to bat velocity. If the bat is not in the lag position, it is difficult for the hitter to use the kinetic link, which will be discussed in the next section.
[FIGURE 9 OMITTED]
[FIGURE 10 OMITTED]
The "lag drill" will help the hitter achieve the proper lag position (figure 9). The hitter starts with the bat resting on the back upper arm. From this position, the hitter performs a load and then swings the bat forward against a padded wall. The objective is to use the torso to accelerate the bat while focusing on dropping the barrel into the lag position (parallel to the ground). The coach should emphasize that the hitter use the rotation of the torso, not the arms, to accelerate the barrel. The hitter should also focus on maximizing the barrel surface area that makes contact with the wall. When properly executed, contact with the wall should produce a loud cracking noise. On contact, the hips of the hitter should be opened completely and facing the wall.
The late swing phase begins when the bat is parallel to the ground and ends at contact with the ball (figure 10). The velocity of the bat head is generated at the hips and shoulders. Ideally, the bat should reach maximum angular velocity immediately before contact. This has been demonstrated in professional hitters (Welch et al., 1995). As the bat moves toward the pitch during the mid-swing phase, there is very little angular movement. That is, the bat is not rotating about a fixed point. Just before contact, the arms begin to slow down as they move in front of the body. This deceleration causes a transfer of momentum to the bat, resulting in angular acceleration of the bat through the hitting zone (DeRenne et al., 1993). It should be noted that the hitter should not "push" the knob of the bat to the ball. More specifically, the arms are not driving the swing at this point. This is supported by decreasing deltoid and tricep activation throughout the swing phase observed in professional hitters (Shaffer et al., 1993). Instead the hitter should "pull" the bat across the body (Robson, 2003). As the shoulders, arms, and bat rotate toward the pitch, centrifugal force attempts to pull the arms away from the body's center of gravity. By resisting this force and pulling the arms across the body, the hitter actually increases bat velocity, much in the same way that figure skaters can increase their rotational velocity by pulling their arms in close (Hamilton & Luttgens, 2002). By narrowing the radius of the path of the hands from the launch position to the point of contact, the hitter minimizes the moment of inertia, thus increasing velocity at contact.
[FIGURE 11 OMITTED]
The "hat drill" emphasizes a tight hand path. The hitter holds a hat in the armpit of his or her lead arm while taking batting practice or hitting from a tee. While performing a swing, the hitter will focus on minimizing the distance of the hands in relation to the body. If the arc of the hands is too wide, the hat will fall from the hitter's armpit. It should be noted that it is acceptable if the hat falls after contact, due to the follow-through.
The "fence drill" is also useful. The hitter assumes the batting stance beside a fence or wall. An appropriate starting distance would be one bat length between the fence and the hitter's belly button. On command, the hitter performs a dry swing (without a ball involved) without making contact with the wall. The hitter focuses on minimizing the distance of the hands in relation to the body in order to prevent the bat from striking the fence or wall.
The baseball swing is composed of several sequential movements, with no one movement more important than the others. All the movements flow into one another and contribute to the swing as a whole. Large base segments accelerate and pass momentum onto the smaller distal segments later in the swing sequence (DeRenne et al., 1993). When a larger segment begins to decelerate, the velocity of the next segment accelerates as it assumes the momentum lost by the previous segment. This concept is called the "kinetic link."
[FIGURE 12 OMITTED]
As described previously in the phases of the baseball swing, hip rotation starts before shoulder rotation, which is followed by rotation of the arms, wrists, and bat head. Figure 11 depicts the angular hip, shoulder, and bat velocities of four collegiate Division I baseball players. Note how the hips begin to accelerate first, followed by the shoulders, and ending with the bat. In other words, the hips reached peak velocity first (0.119 seconds), the shoulders second (0.153 seconds), and the bat last at the point of contact (PC). If any movement is initiated out of sequence, the hitter loses the ability to use the velocity and momentum of the previous movements, and consequently, the final velocity of the whole movement is diminished (Welch et al., 1995). The bat lag position was previously mentioned as being important for bat velocity. More specifically, the lag position ensures that the bat is the last segment in the kinetic link to be accelerated. The end result is a sequential accumulation of segment velocity, peaking with the bat head at the point of contact. The lag drill is an appropriate drill to teach hitters the concept of the kinetic link. Videotape is also effective for demonstrating the kinetic link.
Follow-through
The follow-through phase begins when the bat makes contact with the ball and ends when the lead shoulder is maximally abducted and externally rotated (figure 12). A hitter's follow-through is largely a matter of personal preference. Whether the follow-through is one-handed or two-handed will have no effect on the batted ball. However, the follow-through should be performed at least at the height of the shoulder in order to increase the time of the bat head in the strike zone (DeRenne et al., 1993).
Recommendations
As explained, changes in swing mechanics can effect bat velocity and bat quickness. The authors believe that hitters should attempt to make swing adjustments that improve bat quickness. Concurrent improvements in bat velocity can also be achieved through the use of flexibility-, strength-, and plyometric-training methods. Furthermore, by improving hand path and the kinetic link, bat velocity at contact may increase. Hitters should understand that although a long swing may generate a higher peak velocity, this peak velocity may not occur at the point of contact. Mechanically speaking, the bottom line is to increase decision time and to arrive at the point of contact with peak velocity. Physiologically speaking, the bottom line is to maximize the ability of the appropriate muscles to shorten rapidly and forcefully, resulting in greater overall bat velocity.
References
Adair, R. K. (1990). The physics of baseball. New York: Harper & Row.
Bennett, G., & Yeager, C. (2000). The stride is key to hitting. Strategies, 13(4), 5-7.
Bunn, J. W. (1965). Scientific principles of coaching. New York: Prentice-Hall.
Crisco, J. J., Greenwald, R. M., Blume, J. D., & Penna, L. H. (2002). Batting performance of wood and metal baseball bats. Medicine & Science in Sports & Exercise, 34, 1675-1684.
DeRenne, C., Stellar, T., & Blitzbau, A. (1993). High-tech hitting: Science vs. tradition. Laguna Hills, CA: Bio-Kinetics.
Garhammer, J. (1983). A kinesiological analysis of hitting for baseball. National Strength and Conditioning Association Journal, 5(6-7), 70-71.
Hamilton, N. P., & Luttgens, K. (2002). Kinesiology: Scientific basis of human motion. New York: McGraw-Hill.
Hay, J. G. (1993). The biomechanics of sports techniques. Englewood Cliffs, NJ: Prentice-Hall.
Hudgens, D. (1997). Hitting for excellence. Scottsdale, AZ: Living Water.
Lefebvre, J. (1983). Hitting the baseball: Let's understand the process. National Strength and Conditioning Association Journal, 5(2), 6.
Robson, T. (2003). The hitting edge. Champaign, IL: Human Kinetics.
Shaffer, B., Jobe, F., Pink, M., & Perry, J. (1993). Baseball batting: An electromyographic study. Clinical Orthopaedics and Related Research, 292, 285-293.
Stellar, T., House, T., DeRenne, C., & Blitzblau, A. (1993). The absolutes of hitting: Dynamic balance, kinetic link, axis of rotation and bat lag [Motion picture]. (Available from Bio-Kinetics, 8385 S. Allen St., Suite 103, Sandy, UT 84070.
Swimley, P. S. (1964). A cinematographic analysis of two selected baseball swings. Unpublished master's thesis. Sacramento State College, Sacramento, CA.
Welch, C., Banks, S., Cook, F., & Draovitch, P. (1995). Hitting a baseball: a biomechanical description. Journal of Orthopaedic Sports Physical Therapy, 22, 193-201.
Williams, T. (1971). The science of hitting. New York: Simon and Schuster.
Robin J. Lund (robin.lund@uni.edu) is an assistant professor in the School of Health, Physical Education, and Leisure Services, at the University of Northern Iowa, Cedar Falls, IA 50614-0241. Dan Heefner (dheefner@Creighton.edu) is an assistant baseball coach at Dallas Baptist University, Dallas, TX 75211.
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Training the baseball hitter: what does research say? Guided too long by folklore, baseball batting has become a science.
JOPERD--The Journal of Physical Education, Recreation & Dance March , 2005
Former baseball star Jim Lefebvre (1983) claimed that hitting a baseball may be the most talked about but least understood skill in all of sports. Historically, hitting instruction has been based on intuitive thinking by "hitting gurus," rather than on scientific fact, which has contributed to this lack of understanding (DeRenne, Stellar, & Blitzbau, 1993). Compared to other sports, baseball has lagged in regard to the application of science to the development of the swing and training methodology.
Although athletes and coaches have many hitting drills to choose from, few of these drills are grounded in science. A thorough understanding of the mechanics of the baseball swing is critical to formulating a sound training methodology. Therefore, the purpose of this article is to use previous studies to describe proper swing mechanics and to provide a few examples of drills that could be used to train these mechanics. However, the concepts of bat velocity and bat quickness must be considered before any discussion of swing mechanics. Recognizing the difference between these two, often misunderstood, concepts is a prerequisite for understanding the mechanics of the baseball swing.
[FIGURE 1 OMITTED]
Bat Velocity and Bat Quickness
Bat velocity is the speed at which the bat head is traveling at the moment of contact (Stellar, House, DeRenne, & Blitzblau, 1993). Bat velocity is important for several reasons. According to the equation, force equals mass times acceleration, the greater the velocity of the bat at contact, the greater the force that can be imparted to the ball and the farther the ball will travel once it is hit (Hamilton & Luttgens, 2002). In addition, if energy equals one-half mass times velocity squared, a bat swung with more velocity will result in greater energy imparted to the ball. In short, the higher the velocity of the bat at contact, the higher the velocity of the batted ball (Adair, 1990). This is true both for wooden bats and aluminum bats (Crisco, Greenwald, Blume, & Penna, 2002).
Bat quickness is the time it takes to move the bat head from the launch position to contact with the ball, measured in seconds (Hay, 1993). The relationship between bat velocity and bat quickness is usually inverse in effect (Stellar et al., 1993). That is, players who exhibit high bat velocities tend to have poor bat quickness (high swing times). The bat quickness of major league hitters has been calculated to be 0.14 to 0.15 of a second in contact hitters, and 0.17 to 0.18 in power hitters, demonstrating the inverse relationship between the two performance variables (Stellar et al., 1993). This relationship has been attributed to changes in decision time (Hay, 1993). Decision time is the amount of time the hitter has to read the pitch and decide if, when, and where to swing the bat. As bat quickness improves, decision time increases, and the chance of making a correct decision increases.
Variation in swing mechanics can account for much of the observed relationship between bat velocity and bat quickness. For example, as bat wrap increases, bat velocity increases, but bat quickness becomes slower. Bat wrap refers to the degree to which the bat points toward the pitcher in the launch position (figure 1). The greater the wrap, the farther the barrel of the bat must travel to get to the contact zone. The greater distance traveled results in higher swing times (slower bat quickness), but the additional time allows the hitter to generate more bat velocity. Varying the extension of the lead elbow has a similar effect. In other words, as extension increases, so does the length of this segment as a lever. The end result is a wider radius from launch to contact and a subsequent increase in angular velocity and swing time (Bunn, 1965).
[FIGURE 2 OMITTED]
It is important to realize that high bat velocity does not necessarily mean a more productive hitter. This can be confirmed by the lower batting averages typically observed in power hitters. Similarly, great bat quickness with poor bat velocity will most likely result in poor power statistics such as extra base hits and slugging percentage. A hitter must combine bat velocity and bat quickness in order to maximize productivity. Players who have great bat velocity and outstanding bat quickness hit for both power and a high average. These players are the superstars of the game. There are, of course, other factors that play a role in hitting productivity. These include, but are not limited to, visual skills, pitch selection, and confidence. Due to the limited scope of this article, these factors will not be discussed.
Improving bat velocity without compromising bat quickness can be accomplished with strength and power training. That is, the associated musculature is trained to contract more forcefully and rapidly without any changes in swing mechanics (i.e., increased bat wrap). Using electromyography, Shaffer, Jobe, Pink, and Perry (1993) explored the muscle activation patterns of various muscles during the baseball swing in professional baseball players. The authors concluded that hitters should emphasize the abdominals and muscles of the lower back due to the high muscle activity observed in these muscle groups throughout the swing.
Although most abdominal and lower back exercise would benefit the hitter, those exercises that involve twisting of the torso are more specific to the movement patterns of the baseball swing (Garhammer, 1983). Once a base level of local muscle strength and endurance has been established via various crunches and lower back exercises, hitters can begin to incorporate resistance with rotation. An example of such a drill is the hitter's toss, a rotational plyometric exercise depicted in figure 2. In this drill, the hitter loads the muscles of the trunk and then throws the medicine ball as forcefully as possible while mimicking the mechanics of the swing as best as possible. Theoretically, if the ability of the musculature to contract rapidly increases, and swing mechanics remain unchanged, both bat velocity and bat quickness could be improved concurrently.
Baseball Swing Mechanics
In order to simplify data analysis, the study by Shaffer et al. (1993) divided the swing into four separate phases: the wind-up, pre-swing, swing, and follow-through. Because of its effect on these four phases, the hitter's stance before initiating the swing will also be discussed.
Stance
The manner in which a hitter stands in the batters' box before the pitch is a subject that lacks scientific evidence (Hay, 1993). Although hitters' stances are individualized, it should be noted that most major league hitters have certain characteristics in common. Identifying these characteristics is important because problems with the stance can lead to problems with the swing.
The first characteristic of the major league stance is dynamic balance. This means that the head is over the center of gravity and the center of gravity is equidistant between the balls of the feet. If the hitter is unbalanced, the hitter will not be able to create a base of support to execute the proper swing mechanics (DeRenne et al., 1993).
The second characteristic of the major league stance involves the position of the head. The head should be facing the pitcher in such a way that the batter can see the pitcher with both eyes. In addition, there should be minimal tilt of the head so that eyes are parallel with the ground. Starting with the head in this position will help to keep the distance between the chin and the lead shoulder relatively constant throughout the swing (DeRenne et al., 1993).
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
The third characteristic is rhythm. Most major league hitters incorporate rhythm while waiting for the pitch in their stance (Hudgens, 1997). Rhythm keeps the body free of tension and aids in the timing of the pitch. The hitter's rhythm starts with large movements and slows down to a smaller movement just before the swing. Most successful major league hitters slow down their movement or rhythm just before they stride. Videotape and mirrors are useful tools for improving the stance. Hitters may think they are incorporating balance, proper head position, and rhythm in their stance, but on seeing their stance in a practice or game situation, they may be surprised to observe otherwise.
Wind-up Phase
The wind-up phase begins as the lead foot leaves the ground and ends when it returns back to the ground (figure 3). This phase may also be thought of as the stride. The stride is a step taken by the hitter in the direction of the pitcher (Bennett & Yeager, 2002). The stride is a preparatory movement that allows the hitter to generate linear momentum in the direction of the pitch. This momentum is desirable unless the hitter is unable to maintain balance (DeRenne et al., 1993). As the stride takes place, the hands, shoulders, and hips also move. The hands move back toward the rear shoulder until they are located over or behind the rear foot, and the shoulders and hips rotate inward (Welch, Banks, Cook, & Draovitch, 1995).
[FIGURE 5 OMITTED]
The stride must be completed before any other forward movement is made in the swing. In other words, rotation of the torso toward the pitched ball should not take place until the stride heel makes contact with the ground (DeRenne et al., 1993). The baseball swing is initiated, not by the back leg as many coaches teach, but by the front heel making contact with the ground (Welch et al., 1995). No further linear movement of the body should occur once the stride heel lands. If the lead foot is not down before the pitched ball is half way to home plate, the hitter will not have enough time to rotate the trunk, shoulders, and bat into contact with the ball.
The length of the hitter's stride also affects his or her reaction time. Stride length is directly proportional to linear body movement, therefore a longer stride will move the head and eyes that much closer to the pitched ball. For example, if an 85 miles-per-hour pitch is thrown to a hitter with a five-inch stride, the same pitch will have an effective speed of 88.5 miles-per-hour to a hitter with a 15-inch stride. A short stride also increases the chance of the stride being consistent every pitch (Hay, 1993).
The "command soft-toss drill" is an effective means for teaching the stride (figure 4). During the soft toss, the coach provides a verbal cue of when to stride. Once the stride is down, the coach waits and then tosses the ball so that the hitter can hit it into a net. The objective of the drill is to separate the stride from the swing, which teaches the hitter to stop the linear movement once the stride foot has made contact with the ground. This drill also emphasizes the importance of an early stride (timing) and allows the coach to provide feedback in regard to the length and direction of the stride.
[FIGURE 6 OMITTED]
Before ending this discussion of the stride, the concept of inward turn must be addressed. Ted Williams (1971) called the inward turn a "hip cock" and compared it to a pendulum. It is a movement of the hips during the stride so that the hitter can countermove them more efficiently during the swing. Scientific research supports Williams' intuitive reasoning. Welch et al. (1995) reported that hitters rotated their upper bodies in the opposite direction of the swing starting with the arms and shoulders, followed by the hips.
There is a difference of opinion as to when the inward turn takes place. One study reported that the inward turn occurs while the hitter is shifting his or her weight against the rear leg before the stride (Welch et al., 1995). Other sources suggest that the inward turn reaches its maximum during the stride (Hay, 1993; Swimley, 1964; Williams, 1971). Regardless of when the inward turn occurs, its importance is obvious in regard to the generation of bat velocity. It should also be noted that too much inward turn may make it impossible to keep both eyes forward, and therefore it may be detrimental to hitting performance.
An example of a drill designed to emphasize the inward turn is the "load drill" (figure 5). With a ball placed on a tee, the hitter starts the drill in the contact position. From here, the hitter recoils backwards under control. After achieving some degree of inward turn, the hitter then proceeds with striking the ball. The objective of this drill is to perform the inward turn while focusing on swing rhythm and swing cadence. Additionally, the coach can provide feedback as to whether there is enough, or too much, inward turn.
[FIGURE 7 OMITTED]
Pre-Swing Phase
The pre-swing phase is very short. It begins when the lead foot reestablishes contact with the ground, and it ends when the actual swing begins (figure 6). During the pre-swing phase, the hands, shoulders, and hips eventually stop moving. Once this occurs, the hitter has reached the launch position. From the launch position, the hitter then decides whether or not to swing at the pitch. The launch position of the hands is located near the back shoulder, with the hands over or behind the rear foot (Hudgens, 1997). The rear elbow should move upward when the hands reach this position (DeRenne et al., 1993). The hands have not initiated any forward movement up to this point (Bennett & Yeager, 2000).
Generally speaking, power hitters have more bat wrap than contact hitters in the launch position (Stellar et al., 1993). Virtually all players, including contact hitters, have some degree of bat wrap. Without bat wrap, the wrists will not be abducted (radially deviated) before the swing phase. Adduction of the abducted wrists is the last event to occur in the swing sequence.
As with the stance, the use of videotape can help the hitter achieve the proper launch position. The use of videotape in this instance can be an invaluable tool to the young hitter.
Swing Phase
The swing phase can be partitioned into three sub-phases; early, mid, and late (Schaffer et al., 1993). The early swing phase begins when the pelvis begins to uncoil and ends when the barrel of the bat is perpendicular with the ground (figure 7). As the hips uncoil, the shoulders continue to coil in the opposite direction. This counter-rotation of the shoulders stretches the trunk muscles. This stretch enhances the ability of the musculature to contract and puts the torso in a position in which it can unwind powerfully (Garhammer, 1983). Toward the end of the early swing phase, the shoulders will begin to rotate in the same direction as the hips, bringing the bat forward toward the pitch.
Torso flexibility is clearly important in order for the hitter to achieve counter-rotation of the shoulders as the hips begin to uncoil. If the torso is inflexible, the shoulders will rotate prematurely as the hips begin to uncoil, disrupting the hitter's timing. Torso twists performed with the bat as well as static stretching with a partner are examples of appropriate hitter-specific drills to improve torso flexibility.
[FIGURE 8 OMITTED]
The mid-swing phase begins when the bat is perpendicular to the ground and ends when the bat is parallel to the ground (figure 8). "Bat lag" is the term used to describe the position of the bat as parallel to the ground (DeRenne et al., 1993). The shoulders continue to rotate toward the pitch, taking the arms and the bat with them. As the bat moves forward, the barrel will drop automatically into bat lag. The bat lag position is important in regard to bat velocity. If the bat is not in the lag position, it is difficult for the hitter to use the kinetic link, which will be discussed in the next section.
[FIGURE 9 OMITTED]
[FIGURE 10 OMITTED]
The "lag drill" will help the hitter achieve the proper lag position (figure 9). The hitter starts with the bat resting on the back upper arm. From this position, the hitter performs a load and then swings the bat forward against a padded wall. The objective is to use the torso to accelerate the bat while focusing on dropping the barrel into the lag position (parallel to the ground). The coach should emphasize that the hitter use the rotation of the torso, not the arms, to accelerate the barrel. The hitter should also focus on maximizing the barrel surface area that makes contact with the wall. When properly executed, contact with the wall should produce a loud cracking noise. On contact, the hips of the hitter should be opened completely and facing the wall.
The late swing phase begins when the bat is parallel to the ground and ends at contact with the ball (figure 10). The velocity of the bat head is generated at the hips and shoulders. Ideally, the bat should reach maximum angular velocity immediately before contact. This has been demonstrated in professional hitters (Welch et al., 1995). As the bat moves toward the pitch during the mid-swing phase, there is very little angular movement. That is, the bat is not rotating about a fixed point. Just before contact, the arms begin to slow down as they move in front of the body. This deceleration causes a transfer of momentum to the bat, resulting in angular acceleration of the bat through the hitting zone (DeRenne et al., 1993). It should be noted that the hitter should not "push" the knob of the bat to the ball. More specifically, the arms are not driving the swing at this point. This is supported by decreasing deltoid and tricep activation throughout the swing phase observed in professional hitters (Shaffer et al., 1993). Instead the hitter should "pull" the bat across the body (Robson, 2003). As the shoulders, arms, and bat rotate toward the pitch, centrifugal force attempts to pull the arms away from the body's center of gravity. By resisting this force and pulling the arms across the body, the hitter actually increases bat velocity, much in the same way that figure skaters can increase their rotational velocity by pulling their arms in close (Hamilton & Luttgens, 2002). By narrowing the radius of the path of the hands from the launch position to the point of contact, the hitter minimizes the moment of inertia, thus increasing velocity at contact.
[FIGURE 11 OMITTED]
The "hat drill" emphasizes a tight hand path. The hitter holds a hat in the armpit of his or her lead arm while taking batting practice or hitting from a tee. While performing a swing, the hitter will focus on minimizing the distance of the hands in relation to the body. If the arc of the hands is too wide, the hat will fall from the hitter's armpit. It should be noted that it is acceptable if the hat falls after contact, due to the follow-through.
The "fence drill" is also useful. The hitter assumes the batting stance beside a fence or wall. An appropriate starting distance would be one bat length between the fence and the hitter's belly button. On command, the hitter performs a dry swing (without a ball involved) without making contact with the wall. The hitter focuses on minimizing the distance of the hands in relation to the body in order to prevent the bat from striking the fence or wall.
The baseball swing is composed of several sequential movements, with no one movement more important than the others. All the movements flow into one another and contribute to the swing as a whole. Large base segments accelerate and pass momentum onto the smaller distal segments later in the swing sequence (DeRenne et al., 1993). When a larger segment begins to decelerate, the velocity of the next segment accelerates as it assumes the momentum lost by the previous segment. This concept is called the "kinetic link."
[FIGURE 12 OMITTED]
As described previously in the phases of the baseball swing, hip rotation starts before shoulder rotation, which is followed by rotation of the arms, wrists, and bat head. Figure 11 depicts the angular hip, shoulder, and bat velocities of four collegiate Division I baseball players. Note how the hips begin to accelerate first, followed by the shoulders, and ending with the bat. In other words, the hips reached peak velocity first (0.119 seconds), the shoulders second (0.153 seconds), and the bat last at the point of contact (PC). If any movement is initiated out of sequence, the hitter loses the ability to use the velocity and momentum of the previous movements, and consequently, the final velocity of the whole movement is diminished (Welch et al., 1995). The bat lag position was previously mentioned as being important for bat velocity. More specifically, the lag position ensures that the bat is the last segment in the kinetic link to be accelerated. The end result is a sequential accumulation of segment velocity, peaking with the bat head at the point of contact. The lag drill is an appropriate drill to teach hitters the concept of the kinetic link. Videotape is also effective for demonstrating the kinetic link.
Follow-through
The follow-through phase begins when the bat makes contact with the ball and ends when the lead shoulder is maximally abducted and externally rotated (figure 12). A hitter's follow-through is largely a matter of personal preference. Whether the follow-through is one-handed or two-handed will have no effect on the batted ball. However, the follow-through should be performed at least at the height of the shoulder in order to increase the time of the bat head in the strike zone (DeRenne et al., 1993).
Recommendations
As explained, changes in swing mechanics can effect bat velocity and bat quickness. The authors believe that hitters should attempt to make swing adjustments that improve bat quickness. Concurrent improvements in bat velocity can also be achieved through the use of flexibility-, strength-, and plyometric-training methods. Furthermore, by improving hand path and the kinetic link, bat velocity at contact may increase. Hitters should understand that although a long swing may generate a higher peak velocity, this peak velocity may not occur at the point of contact. Mechanically speaking, the bottom line is to increase decision time and to arrive at the point of contact with peak velocity. Physiologically speaking, the bottom line is to maximize the ability of the appropriate muscles to shorten rapidly and forcefully, resulting in greater overall bat velocity.
References
Adair, R. K. (1990). The physics of baseball. New York: Harper & Row.
Bennett, G., & Yeager, C. (2000). The stride is key to hitting. Strategies, 13(4), 5-7.
Bunn, J. W. (1965). Scientific principles of coaching. New York: Prentice-Hall.
Crisco, J. J., Greenwald, R. M., Blume, J. D., & Penna, L. H. (2002). Batting performance of wood and metal baseball bats. Medicine & Science in Sports & Exercise, 34, 1675-1684.
DeRenne, C., Stellar, T., & Blitzbau, A. (1993). High-tech hitting: Science vs. tradition. Laguna Hills, CA: Bio-Kinetics.
Garhammer, J. (1983). A kinesiological analysis of hitting for baseball. National Strength and Conditioning Association Journal, 5(6-7), 70-71.
Hamilton, N. P., & Luttgens, K. (2002). Kinesiology: Scientific basis of human motion. New York: McGraw-Hill.
Hay, J. G. (1993). The biomechanics of sports techniques. Englewood Cliffs, NJ: Prentice-Hall.
Hudgens, D. (1997). Hitting for excellence. Scottsdale, AZ: Living Water.
Lefebvre, J. (1983). Hitting the baseball: Let's understand the process. National Strength and Conditioning Association Journal, 5(2), 6.
Robson, T. (2003). The hitting edge. Champaign, IL: Human Kinetics.
Shaffer, B., Jobe, F., Pink, M., & Perry, J. (1993). Baseball batting: An electromyographic study. Clinical Orthopaedics and Related Research, 292, 285-293.
Stellar, T., House, T., DeRenne, C., & Blitzblau, A. (1993). The absolutes of hitting: Dynamic balance, kinetic link, axis of rotation and bat lag [Motion picture]. (Available from Bio-Kinetics, 8385 S. Allen St., Suite 103, Sandy, UT 84070.
Swimley, P. S. (1964). A cinematographic analysis of two selected baseball swings. Unpublished master's thesis. Sacramento State College, Sacramento, CA.
Welch, C., Banks, S., Cook, F., & Draovitch, P. (1995). Hitting a baseball: a biomechanical description. Journal of Orthopaedic Sports Physical Therapy, 22, 193-201.
Williams, T. (1971). The science of hitting. New York: Simon and Schuster.
Robin J. Lund (robin.lund@uni.edu) is an assistant professor in the School of Health, Physical Education, and Leisure Services, at the University of Northern Iowa, Cedar Falls, IA 50614-0241. Dan Heefner (dheefner@Creighton.edu) is an assistant baseball coach at Dallas Baptist University, Dallas, TX 75211.
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