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«A Choke-Up Grip Facilitates Faster Swing and Stride Times Without Compromising Bat Velocity and Bat Control - 04 by U.S. Sports Academy - The Sport ...»

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A Choke-Up Grip Facilitates Faster Swing and Stride Times Without Compromising Bat Velocity and Bat Control - 04

by U.S. Sports Academy - The Sport Journal - http://thesportjournal.org

A Choke-Up Grip Facilitates Faster Swing and Stride Times

Without Compromising Bat Velocity and Bat Control

by U.S. Sports Academy - Thursday, April 08, 2010

http://thesportjournal.org/article/a-choke-up-grip-facilitates-faster-swing-and-stride-times-withoutcompromising-bat-velocity-and-bat-control/

Submitted by: Coop DeRenne, Charles F. Morgan, Department of Kinesiology & Rehabilitation Science, University of Hawaii; Rafael F. Escamilla, Department of Physical Therapy, California State University, Sacramento, CA; Glenn S. Fleisig, American Sports Medicine Institute, Birmingham, AL Abstract This study investigated the relationship among hitting components and bat control during the normal and choke-up grip swings. Fourteen intercollegiate and professional baseball players were randomly assigned into five hitting groups. Within each group, the following four hitting components were computed to determine the relationship between bat control in two grip conditions (normal; choke-up): (1) Swing time (bat quickness), (2) stride time, (3) bat velocity, and (4) bat-ball contact accuracy. Results indicated significant differences (p =0.01) between choke-up and normal grips in swing time, stride time, and bat velocity. Players using the choke-up grip swing had significant less swing time and stride time than the normal grip swing. Results also indicated significant greater bat velocities (p = 0.01) with normal grip swings than the choke-up grip swings. In addition, further results indicated no significant differences (p =.90) between choke-up and normal grips in bat-ball accuracy. These findings suggest that the choke-up grip facilitates faster swing time and stride time without compromising bat velocity or contact accuracy.

Key words: bat control, bat quickness, stride time, accuracy.

Introduction Historically, since major league baseball established its modern day roots in the early 1900's, the best hitters in the game have studied hitting mechanics to improve their performances (Cobb, 1961; DeRenne, 2007; Gwynn, 1998; Lau, Glossbbrenner, & LaRussa; 1980; Williams, 1970). Though the early day great hall of fame hitters didn't have the advantages of present day high-technology and research-generated information, the majority of those hitters and those of present day agree that by studying and applying swing kinematics will create greater bat control during competition (Alston & Weiskopf, 1972; Cobb, 1961; DeRenne, 2007; Gwynn, 1998; Williams, 1970). From the one of games early great hitters TyCobb (1961), to modern era hall of famer hitter Ted Williams (1970), to eight time major league batting champion and hall of fame hitter Tony Gwynn (1998) and finally to major league home run king great Barry Bonds, these great hitters share in the belief that increasing bat control is essential for successful hitting (Cobb, 1961; Gwynn, 1998; Williams, 1970).

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As intercollegiate baseball evolved in the 29th Century mainly from major league influences, hall of fame intercollegiate head coaches such as Rod Dedeaux (Division I Coach of the 20th Century), John Scolinos (Division II Coach of the 21st Century), Skip Berkman (Division I NCAA Coach of the 1990 Decade), Ron Polk (1978), Jerry Kindall (2000) and Tony Gwynn (1998); and intercollegiate hitting coaches Dr.

Coop DeRenne, (2007), All-American Jerry Kindall (2000), and Tony Gwynn (1998) also recognize the importance of increasing bat control in various offensive situations (e.g., two-strikes on the hitter, hit-andrun play, hit to opposite field) (Delmonico, 1996). Yet, ask any of these great managers or hitters to define bat control, and there would no common answer. Furthmore, when these highly successful intercollegiate hitters and coaches discuss the topic of bat control, the majority agrees that choking up on the bat will increase bat control (Berkow & Kaplan, 1992; Delmonico, 1996; DeRenne, 2007; Gwynn, 1998; Kindall & Winkin, 2000; Polk, 1978; Stallings, J. & Bennett, B. [Eds.], 2003). If in the opinion of these intercollegiate coaches that choking up on the bat is a hitting technique used specifically in various game offensive hitting situations to increase bat control, then it is important for all collegiate hitters, coaches, and hitting coaches to understand what is bat control and how is it improved.

Anecdotal opinions from intercollegiate head coaches and hitting coaches, suggest that increased bat control is a result of choking up on the bat that may or may not aid in increasing bat speed, or bat swing time ("bat quickness ") (Delmonico, 1996; DeRenne, 2007; Gwynn, 1998; Kindall & Winkin, 2000; Polk, 1978; Stallings, J. & Bennett, B. [Eds.], 2003). In addition, intercollegiate hitters believe that as the bat travels through the swing’s range of motion with a choke-up grip, the bat feels lighter and more controllable (a potential psychological factor beyond the scope of this study) (Adair, 1990; Bahill & Karnavas, 1989; Delmonico, 1996; DeRenne, 2007; Gwynn, 1998; Kindall & Winkin, 2000) as compared to the normal grip swing with hands held down at the end of the bat.

Limited hitting research studies has been conducted over the past twenty-five years to determine bat control and associated factors (DeRenne, & Blitzbau, 1990; Escamilla, Fleisig, DeRenne, Taylor, Moorman, Imamura, 2009; Fleisig, Zheng, Stodden, & Andrews, 2002; McIntyre, & Pfautsh, 1982;





Messier, & Owen, 1985; Messier, & Owen, 1986; Szymanski, D.J., DeRenne. C., & Spaniol, F.J., 2009).

Based on limited research on bat control, the primary purposes of this study were to explore the relationship among hitting components (stride time, swing time, bat quickness, bat velocity, and bat-ball accuracy), and bat control during the normal and choke-up grip swings.

MethodParticipants

Fourteen adult baseball players (eight college and six professional players one year removed from college) volunteered to participate and were informed of all risks, hazards and benefits for this study. All participants provided written informed consent as approved by the university’s Office of Research Service’s Committee on Human Studies and the federally mandated Institutional Review Board. All participants were required (1) to be injury-free, (2) have a career batting average of least.300, (3) have choke-up grip hitting experiences at the youth, high school and collegiate levels, (4) and possess good hitting mechanics as determined by the players’ respective hitting coaches (DeRenne, 2007; Race, 1961;

Welch, Banks, Cook, & Draovitch, 1995). The subjects had an average age, weight, and height of

22.2±2.3 y, 84.8±6.6 kg, and 180.6±3.7 cm, respectively. The college and professional participants were

–  –  –

statistically equivalent to each other with respect to age, body mass, body height, bat characteristics, and temporal and kinematic parameters (Escamilla et al., 2009).

Apparatus Radar gun Pitched baseballs were assessed during the batting practice session by an electromagnetic radiation radar (CMI Model JF 100) with a transmission frequency of 10.525 GHz + 25 MHz (DeRenne, Ho, Blitzblau, 1990). Pitched ball velocities were recorded as the ball left the pitching machine. This radar gun has been reported to be a valid and reliable instrument to determine ball exit velocities and is accurate within ±

0.22 m/s (DeRenne et al., 1990).).

High-speed cameras

Two synchronized gen-locked 120 Hz video cameras (Peak Performance Technologies, Inc., Englewood, CO) were optimally positioned to view the hitter. To minimize the effects of digitizing error, the cameras were positioned so that the hitter was as large as possible within the viewing area of the cameras.

Computerized motion analysis system

A 3-D video system (Peak Performance Technologies, Inc., Englewood, CO) was used to manually digitize data for all subjects. A spatial model was created, comprised of the top of the head, centers of the left and right mid-toes (at approximately the head of the third metatarsal), joint centers of the ankles, knees, hips, shoulders, and elbows, mid-point of hands (at approximately the head of the third metacarpal), and proximal and distal end of bat. All points were seen in each camera view. Each of these points was digitized in every video field.

Total body swing kinematics was calculated representing 59 measurements. The three most important swing kinematics that represented the total swing effects to be analyzed for swing grip differences were as follows: stride time, swing time (bat quickness), and estimated linear bat velocity at bat-ball contact.

The swing definition

The swing was defined by four events and three phases. The first event was “lead foot off ground”, which represented the beginning of the stride phase and was defined as the first frame in which the lead foot was no longer in contact with the ground. The next event was “lead foot contact with ground”, which represented the end of the stride phase and was defined as the first frame when the lead foot made contact with the ground. “Lead foot off ground” to “lead foot contact with ground” represented the time duration of the stride phase of the swing. The third event was “hands started to move forward”, which was defined as the first frame that both hands started to move forward towards the pitcher in the positive X direction.

“Lead foot contact with ground” to “hands started to move forward” represented the time duration of the transition phase of the swing (transition between the stride phase and acceleration phase). The last event was “bat-ball contact”, which was defined as the first frame immediately before bat-ball contact. “Hands started to move forward to bat-ball contact” represented the time duration of the acceleration phase of the swing. Therefore, the “swing” was defined as from “lead foot off ground” to “bat-ball contact”, and

–  –  –

consisted of stride, transition, and acceleration phases.

Procedures Familiarization session During the initial familiarization session, all players were given a preliminary choke-up questionnaire to provide background evidence of choking up on the bat during their respective youth, high school and collegiate careers. In order to participate in the choke-up hitting study, all players must have had answered the first three questions with a YES, indicating a substantial history of choking-up during their baseball careers. On question four, the players were asked to list the two top reasons why they decided to choke-up on the bat in competitive games. Bat control was listed by all 14 players (100%) as the number one reason for choking up in the games. The second highest reason was a tie: 50% indicated bat-ball contact accuracy was their second choice; and 50% indicated increased bat speed and bat quickness.

In addition, all players received batting practice instructions. At no time did the investigators reveal the purpose of the study to the players. They were told only that the study was a biomechanical hitting study to determine the mechanical commonalities of the 14 adult swing mechanics.

Batting practice sessions

Bats were self-selected, and average bat weight was 8.5±0.3 N (30.6±1.1 oz) and average bat length was

84.8±1.3 cm (33.4±0.5 inch). The same bat was used for both grip swings. The players were randomly assigned into five hitting groups (4-groups of n =3; 1-group of n=2). Each group was randomized as to the order of group hitting and which bat grip to use. During warm-up, each player had two to-three rounds of hitting with each grip swing to become familiar with the speed and locations of the pitched balls, and the timing of the pitches from the pitching machine. Once the warm-up session was completed, the batting practice sessions commenced.

The first batting session was to determine the kinematic and temporal effects of the normal grip and choke -up grip swings. Each hitter rotated within his respective group until he completed 10 hard, full effort swings with a normal grip (hands as far down as possible on the bat); and 10 hard, full effort swings with a choke-up grip (hands 6.35 cm above the normal grip) as a pitching machine "pitched" baseballs to them. In each group, half the group were randomly assigned to hit with a normal grip first and the other half a choke-up grip first, to eliminate a potential timing confounder. The first three normal grip swings and three choke-up swings that met the following pitch and swing criteria were digitized for each hitter.

Pitches and swings were standardized according to the following criteria: 1) all pitches were between 32.6-33.5 m/s (73-75 mi/h); 2) the pitch had to be a strike on the inner half of the plate from waist to chest high on the hitter; and 3) all swings digitized and used as trials had to be a line drive hit to left-center outfield that carried in flight beyond a 68.6 m (225 feet) marker positioned in left-center field. From pilot data, hitting kinematic and temporal parameters from multiple swings by a hitter that met the above pitch and swing criteria were found to be remarkably similar between swings, typically varying less than 5-10% for each kinematic or temporal parameter.

4 / 10 A Choke-Up Grip Facilitates Faster Swing and Stride Times Without Compromising Bat Velocity and Bat Control - 04 by U.S. Sports Academy - The Sport Journal - http://thesportjournal.org The second batting practice session was conducted 48-hours after the first batting practice session in order to control fatigue. The purpose of this second batting practice session was to determine bat-ball contact accuracy performances of each player as the hitters executed normal and choke-up grip swings during a live practice simulated game. Along with the first batting practice session, this accuracy batting practice session represented a bat control measure. Specifically, each hitter was instructed to swing at ten acceptable strikes over the entire plate, (inside, down the middle and outside part of the plate; from knee to chest high) with each swing grip as to execute successful hits. Two rounds of five swings were performed by each hitter to control fatigue. A successful hit was defined as “putting the ball in play” with



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