Reply to Glazier: “Comment on ‘Influence of shaft length on golf driving performance’”

Abstract

In this study we compared the kinematic features of the throwing motion between young baseball players of different age groups. Forty‐four Japanese baseball players aged 6.1 to 12.3 years who regularly played baseball, including pitchers and position players, had their throwing actions analyzed three‐dimensionally using high speed videography. Of this sample, 26 players aged above 9 years of age were categorized as the senior group, while the remaining 18 were categorized as the junior group. Senior group throwers had greater height and body mass, and produced a greater ball speed than junior group throwers. The throwing arm movement of senior group throwers was similar to that of adult skilled players. However, in the junior group throwers, the shoulder horizontal adduction angle was larger during the arm acceleration phase, and the maximum angular velocities of elbow extension and shoulder internal rotation occurred later than in senior group throwers. These results indicate that players aged above 9 years can acquire a mature throwing arm movement, while players younger than that will use an immature motion. A possible reason why these differences were shown is that the official baseball is relatively heavy for junior group throwers; they would be better advised to use a lighter ball in throwing practice.     

Quantitative analysis of kinematics and kinetics of catchers throwing to second base

Abstract

The catcher has the most demanding position in the games of baseball and softball with no regulations on how many throws they make during game. It was the purpose of this study to describe the kinematics and kinetics of the throwing motion in catchers when throwing down to second base. It was hypothesised that younger and older catchers would display significantly different throwing kinematics and kinetics. Thirty-eight baseball and softball catchers volunteered to participate. Twenty participants were considered younger (aged 9–14, 10.95 ± 1.76 years, 151.11 ± 15.64 cm, 47.94 ± 18.84 kg) and 18 were deemed the older group (aged 15–23, 18.11 ± 2.61 years, 170.91 ± 8.67 cm, 74.88 ± 10.74 kg). Participants received a pitch and completed five accurate throws to second base in full catching gear. The average ball speed of the older catchers was 21 ± 3.58 meters per second (47 ± 8.02 mph) while the younger catchers averaged 17.2 ± 4.0 meters per second (38.6 ± 8.96 mph). Older catchers had greater shoulder elevation at ball release and significantly greater shoulder external rotation at foot contact and shoulder maximum external rotation than younger catchers. It is clear that chronological age plays a role in the throwing mechanics observed in catchers throwing down to second base, however the effects of these differences are not fully understood (i.e., skeletal maturity, experience, strength).     

Kinematic and kinetic comparisons between American and Korean professional baseball pitchers

The purpose of this study was to quantify and compare kinematic, temporal, and kinetic characteristics of American and Korean professional pitchers in order to investigate differences in pitching mechanics, performance, and injury risks among two different cultures and populations of baseball pitchers. Eleven American and eight Korean healthy professional baseball pitchers threw multiple fastball pitches off an indoor throwing mound positioned at regulation distance from home plate. A Motion Analysis three-dimensional automatic digitizing system was used to collect 200 Hz video data from four electronically synchronized cameras. Twenty kinematic, six temporal, and 11 kinetic variables were analyzed at lead foot contact, during the arm cocking and arm acceleration phases, at ball release, and during the arm deceleration phase. A radar gun was used to quantify ball velocity. At lead foot contact, the American pitchers had significantly greater horizontal abduction of the throwing shoulder, while Korean pitchers exhibited significantly greater abduction and external rotation of the throwing shoulder. During arm cocking, the American pitchers displayed significantly greater maximum shoulder external rotation and maximum pelvis angular velocity. At the instant of ball release, the American pitchers had significantly greater forward trunk tilt and ball velocity and significantly less knee flexion, which help explain why the American pitchers had 10% greater ball velocity compared to the Korean pitchers. The American pitchers had significantly greater maximum shoulder internal rotation torque and maximum elbow varus torque during arm cocking, significantly greater elbow flexion torque during arm acceleration, and significantly greater shoulder and elbow proximal forces during arm deceleration. While greater shoulder and elbow forces and torques generated in the American pitchers helped generate greater ball velocity for the American group, these greater kinetics may predispose this group to a higher risk of shoulder and elbow injuries.     

Baseball

The purpose of this study was to quantify and compare kinematic, temporal, and kinetic characteristics of American and Korean professional pitchers in order to investigate differences in pitching mechanics, performance, and injury risks among two different cultures and populations of baseball pitchers. Eleven American and eight Korean healthy professional baseball pitchers threw multiple fastball pitches off an indoor throwing mound positioned at regulation distance from home plate. A Motion Analysis three‐dimensional automatic digitizing system was used to collect 200 Hz video data from four electronically synchronized cameras. Twenty kinematic, six temporal, and 11 kinetic variables were analyzed at lead foot contact, during the arm cocking and arm acceleration phases, at ball release, and during the arm deceleration phase. A radar gun was used to quantify ball velocity. At lead foot contact, the American pitchers had significantly greater horizontal abduction of the throwing shoulder, while Korean pitchers exhibited significantly greater abduction and external rotation of the throwing shoulder. During arm cocking, the American pitchers displayed significantly greater maximum shoulder external rotation and maximum pelvis angular velocity. At the instant of ball release, the American pitchers had significantly greater forward trunk tilt and ball velocity and significantly less knee flexion, which help explain why the American pitchers had 10% greater ball velocity compared to the Korean pitchers. The American pitchers had significantly greater maximum shoulder internal rotation torque and maximum elbow varus torque during arm cocking, significantly greater elbow flexion torque during arm acceleration, and significantly greater shoulder and elbow proximal forces during arm deceleration. While greater shoulder and elbow forces and torques generated in the American pitchers helped generate greater ball velocity for the American group, these greater kinetics may predispose this group to a higher risk of shoulder and elbow injuries.     

Kinematic comparisons of 1996 Olympic baseball pitchers

The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P ? 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.     

Kinematic comparisons of 1996 Olympic baseball pitchers

The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P < 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.     

Contributions of the muscular torques and motion-dependent torques to generate rapid elbow extension during overhand baseball pitching

Some studies have reported that overarm baseball pitching shows a proximal to distal sequential joint motion including a rapid extension of the elbow. It has been suggested that the rapid elbow extension just before ball release is not due to the action of the elbow extensor muscles, but the underlying mechanisms are not so clear. The purpose of this study was to determine the contributions of each joint muscular- and motion-dependent torques, including the upper trunk and throwing arm joints to generate the rapid elbow extension during baseball pitching. The right handed throwing motions of three baseball pitchers were recorded using five high-speed video cameras and the positional data were calculated using the direct linear transformation method. A throwing arm dynamic model of the upper trunk and throwing arm joints was then used, including 10 degrees of freedom, to calculate the throwing arm joint muscular-, throwing arm and upper trunk joint motion-, gravity-, and external force-dependent components that contribute to the maximum elbow extension angular velocity. The results showed that the rapid elbow extension was primarily due to the upper trunk counterclockwise rotation and shoulder horizontal adduction angular velocity-dependent torques. This study implied that the trunk counterclockwise rotators and shoulder horizontal adductors generate positive torques to maintain the angular velocities of the upper trunk counterclockwise rotation and shoulder horizontal adduction may play a key role in producing the rapid elbow extension.     

Coordination pattern of baseball pitching among young pitchers of various ages and velocity levels

This study compared the whole-body movement coordination of pitching among 72 baseball players of various ages and velocity levels. Participants were classified as senior, junior, and little according to their age, with each group comprising 24 players. The velocity levels of the high-velocity (the top eight) and low-velocity (the lowest eight) groups were classified according to their pitching velocity. During pitching, the coordinates of 15 markers attached to the major joints of the whole-body movement system were collected for analysis. Sixteen kinematic parameters were calculated to compare the groups and velocity levels. Principal component analysis (PCA) was conducted to quantify the coordination pattern of pitching movement. The results were as follows: (1) five position and two velocity parameters significantly differed among the age groups, and two position and one velocity parameters significantly differed between the high- and low-velocity groups. (2) The coordination patterns of pitching movement could be described using three components, of which the eigenvalues and contents varied according to age and velocity level. In conclusion, the senior and junior players showed greater elbow angular velocity, whereas the little players exhibited a wider shoulder angle only at the beginning of pitching. The players with high velocity exhibited higher trunk and shoulder rotation velocity. The variations among groups found using PCA and kinematics parameter analyses were consistent.     

Cricket

The laws of bowling in cricket state ‘a ball is fairly delivered in respect of the arm if, once the bowler's arm has reached the level of the shoulder in the delivery swing, the elbow joint is not straightened partially or completely from that point until the ball has left the hand’. Recently two prominent bowlers, under suspicion for transgressing this law, suggested that they are not ‘throwing’ but due to an elbow deformity are forced to bowl with a bent bowling arm. This study examined whether such bowlers can produce an additional contribution to wrist/ball release speed by internal rotation of the upper arm. The kinematics of a bowling arm were calculated using a simple two‐link model (upper arm and forearm). Using reported internal rotation speeds of the upper arm from baseball and waterpolo, and bowling arm kinematics from cricket, the change in wrist speed was calculated as a function of effective arm length, and wrist distance from the internal rotation axis. A significant increase in wrist speed was noted. This suggests that bowlers who can maintain a fixed elbow flexion during delivery can produce distinctly greater wrist/ball speeds by using upper arm internal rotation.     

Self-determination,stage of readiness to change for exercise,and frequency of physical activity in young people

Abstract

Release velocity and accuracy are vital components of throwing performance. However, there is no published research on these parameters for throwing in cricket. In this study, we investigated the throwing performance of 110 cricket players from six different populations: elite senior males, elite under-19 junior males, elite under-17 junior males, elite senior females, elite under-19 junior females, and sub-elite senior males. Based on a specifically designed cricket throwing test, participants were assessed for (1) maximal throwing velocity and (2) throwing accuracy at maximal velocity and at three sub-maximal velocities. Elite senior males exhibited the highest peak and mean maximal throwing velocities (P≤0.001). Furthermore, the groups of males had significantly higher peak and mean maximal throwing velocities than the groups of females (P≤0.01). A speed–accuracy trade-off existed such that all groups demonstrated improved accuracy scores at velocities between 75% and 85% maximal throwing velocity compared with 50% maximal throwing velocity and 100% perceived maximal exertion. The results indicate that sex, training experience (years training), and training volume (training time per week) may contribute to throwing performance in cricket players. Further research should focus on understanding the mechanisms behind the observed differences between these groups. This is the first study to describe the inherent throwing profiles of different cricket playing populations. Potentially, we have identified stimulus material for future training developments.     

Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.     

Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals

We tested the hypothesis that variability in the timing of ball release in overarm throws affects ball speed. Nine unskilled and six skilled throwers made 30 throws fast and accurately from a sitting and standing position. Angular positions of finger and arm segments were recorded with search-coils at 1000 Hz; ball speed was measured with a radar gun. The time of ball release from the fingertips was measured with respect to seven arm kinematic reference points. Mean timing windows for ball release were 28?ms for unskilled throwers and 7?ms for skilled throwers. Mixed-model analyses of variance showed that a there was a statistically significant relationship between ball speed and the timing of ball release in unskilled throwers, but not in skilled throwers. This was presumably due to the difference in variability of the timing of ball release between the two groups. In contrast, skilled throwers showed a relationship between ball speed and peak forearm angular velocity (one measure of arm speed). We conclude that although variability in the timing of ball release can affect ball speed, this is only a major factor in unskilled throwers. When skilled throwers throw fast, variability in ball speed is due to variability in arm speed.     

Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals

We tested the hypothesis that variability in the timing of ball release in overarm throws affects ball speed. Nine unskilled and six skilled throwers made 30 throws fast and accurately from a sitting and standing position. Angular positions of finger and arm segments were recorded with search-coils at 1000 Hz; ball speed was measured with a radar gun. The time of ball release from the fingertips was measured with respect to seven arm kinematic reference points. Mean timing windows for ball release were 28 ms for unskilled throwers and 7 ms for skilled throwers. Mixed-model analyses of variance showed that a there was a statistically significant relationship between ball speed and the timing of ball release in unskilled throwers, but not in skilled throwers. This was presumably due to the difference in variability of the timing of ball release between the two groups. In contrast, skilled throwers showed a relationship between ball speed and peak forearm angular velocity (one measure of arm speed). We conclude that although variability in the timing of ball release can affect ball speed, this is only a major factor in unskilled throwers. When skilled throwers throw fast, variability in ball speed is due to variability in arm speed.     

Kinematics used by world class tennis players to produce high-velocity serves

The purpose of this study was to quantify ranges and speeds of movement, from shoulder external rotation to ball impact, in the tennis service actions of world class players. Two electronically synchronised 200 Hz video cameras were used to record 20 tennis players during singles competition at the Sydney 2000 Olympic games. Three-dimensional motion of 20 landmarks on each player and racquet were manually digitized. Based upon the mean values for this group, the elbow flexed to 104 degrees and the upper arm rotated into 172 degrees of shoulder external rotation as the front knee extended. From this cocked position, there was a rapid sequence of segment rotations. The order of maximum angular velocities was trunk tilt (280 degrees/s), upper torso rotation (870 degrees/s), pelvis rotation (440 degrees/s), elbow extension (1510 degrees/s), wrist flexion (1950 degrees/s), and shoulder internal rotation. Shoulder internal rotation was greater for males (2420 degrees/s) than females (1370 degrees/s), which may be related to the faster ball velocity produced by the males (50.8 m/s) than the females (41.5 m/s). Although both genders produced segment rotations in the same order, maximum upper torso velocity occurred earlier for females (0.075 s before impact) than for males (0.058 s). At impact, the trunk was tilted 48 degrees above horizontal, the arm was abducted 101 degrees and the elbow, wrist, and lead knee were slightly flexed. Male and female players should be trained to develop the kinematics measured in this study in order to produce effective high-velocity serves.     

Kinematics of preferred and non-preferred handballing in Australian football

In Australian football (AF), handballing proficiently with both the preferred and non-preferred arm is important at elite levels; yet, little information is available for handballing on the non-preferred arm. This study compared preferred and non-preferred arm handballing techniques. Optotrak Certus (100 Hz) collected three-dimensional data for 19 elite AF players performing handballs with the preferred and non-preferred arms. Position data, range of motion (ROM), and linear and angular velocities were collected and compared between preferred and non-preferred arms using dependent t-tests. The preferred arm exhibited significantly greater forearm and humerus ROM and angular velocity and significantly greater shoulder angular velocity at ball contact compared to the non-preferred arm. In addition, the preferred arm produced a significantly greater range of lateral bend and maximum lower-trunk speed, maximum strike-side hip speed and hand speed at ball contact than the non-preferred arm. The non-preferred arm exhibited a significantly greater shoulder angle and lower- and upper-trunk orientation angle, but significantly lower support-elbow angle, trunk ROM, and trunk rotation velocity compared to the preferred arm. Reduced ROM and angular velocities found in non-preferred arm handballs indicates a reduction in the degrees of freedom and a less developed skill. Findings have implication for development of handballing on the non-preferred arm.     

Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players

Abstract

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.     

The associations of selected technical parameters with discus throwing performance: A cross-sectional study

The aim of this study was to identify associations between discus throwing performance and the technical parameters of: hip–shoulder and shoulder–arm separation, trunk forward–backward tilt, and throwing-arm elevation angles. Video data of male and female discus throwers' competitive performances were captured during major competitions. Real-life three-dimensional coordinates of 21 body landmarks, and the discus's centre, were obtained for 94 trials using the direct linear transformation procedure. Each technical parameter was reduced at six critical instants. The trend of each parameter across four standards of performance was analysed separately for both sexes. For the female throwers, hip–shoulder and shoulder–arm separations after the flight phase, as well as forward–backward trunk tilts at the beginning and end of the throwing procedure were associated with performance. For male throwers, only the hip–shoulder separation immediately before the flight phase was associated with performance. These findings suggest that the relationships between technical parameters and discus throwing performance are different for males and females. Our results suggest that elite female discus throwers are reliant on effective technique throughout the throwing procedure to achieve long distances, whereas male discus throwers may have a relatively homogeneous technique, and a dependence on physical strength to achieve their long throws.     

Analysis of the relation between throwing speed and throwing accuracy in team-handball according to instruction

Abstract

This study examines the differences between expert and novice team-handball players in their sensitivity to instructions that emphasize speed or precision requirements. The effects of instructions on throwing speed and accuracy of a handball over arm throw and the speed–accuracy trade-off in experts and novices is revisited. An expert group (n=18) with a training experience of more than 10 years, and a novice group (n=24) without experience in team-handball, took part in the study. The participants were asked to throw to targets located at different positions following instructions emphasizing accuracy and instructions emphasizing accuracy and speed. Throwing speed was measured with a speed gun radar, and the centre of the ball when the ball entered the goal was digitalized for accuracy. Under these experimental conditions, the novice group was sensitive to instructions for reducing throwing speed and increasing accuracy when instructions emphasized accuracy. The expert group increased throwing speed when the instructions emphasized speed, but was not less accurate. The results indicate that it is advisable for experts’ speed to be close to maximum speed since it does not seem to have a significant effect on accuracy of the throw.     

Kinematics and kinetics of youth baseball pitching with standard and lightweight balls

Because youth athletes are smaller and weaker than their adult counterparts, smaller equipment and fields are often used in youth sports. Previous research has shown that youth baseball pitchers use similar motions to older pitchers, but generate lower kinetics and angular velocities at the shoulder and elbow. The purpose of this study was to determine potential biomechanical benefits for youth pitchers to use lighter baseballs. Thirty-four youth (11.1 ± 0.7 years) pitchers pitched both standard [5 ounce (142 g)] and lightweight [4 ounce(113 g)] baseballs in a laboratory setting. Kinematic and kinetic parameters were measured with a six-camera high-speed motion analysis system. Three repeated measures MANOVAs were used to compare (p > 0.05) position, velocity, and kinetic parameters between the standard and lightweight baseballs. Subjective data were also collected. Pitching the lightweight ball produced no difference in arm position, but greater shoulder, elbow, and ball velocities. With the lightweight ball, pitchers produced decreased kinetics.Post-hoc analysis of the kinetic data revealed significant decreases in elbow varus torque and shoulder internal rotation torque. The data suggest that playing with lightweight baseballs may reduce the risk of overuse injury in the youth pitcher and also help develop arm speed. However, before introducing lightweight baseballs into the youth game, the effect of lighter, faster pitched balls for the batters and fielders should also be considered.     

Comparison of range of motion tests with throwing kinematics in elite team handball players

The aim of this study was to compare the active and passive range of motion (ROM) of the glenohumeral external rotation with the maximal external rotation and throwing performance during different throws with different wind-up techniques in elite team handball players. Twenty-two elite team handball players participated in the study in which the maximal ball release velocity and maximal external rotation during standing, with run-up and jump throws with two types of wind-ups were measured together with the maximal active and passive glenohumeral ROM of the external rotation, lying supine on a bench. Higher maximal external rotation was found during the throws with the whip-like wind-up in comparison to circular-like wind-up throws together with a lower external rotation during the active ROM test. No correlations were found between the ROM of the external rotation with the maximal ball release velocity and the maximal external rotation measured during the throws. It was concluded that ROM of the external rotation measured on the bench does not give any information about the maximal throwing performance or the external rotation angle during throwing and therefore cannot be used to identify potential fast throwers or injuries in elite team handball players.