Bat speed, trajectory, and timing for collegiate baseball batters hitting a stationary ball

The aims of this study were to examine whether batters hit stationary balls at the time of peak speed of the bat head and whether the impact occurs at the lowest point of the bat trajectory. Eight university baseball players hit three balls, each hung with a string; each ball was made of a different material and was different in weight. Bat movement was captured by four 240-Hz infrared cameras and analysed three-dimensionally. Time for peak speed of the bat head varied according to the conditions. When stationary balls of standard weight were used, the bat head was at maximum speed at impact with the ball; then, it decelerated drastically owing to the impact. In contrast, maximum speed was obtained after impact when lightweight stationary balls were used. The time-speed profile of the bat head before impact in the lightweight ball condition was identical with that in the standard weight ball condition. Regardless of conditions, the timing of the lowest point of the bat head was nearly identical for each batter and most participants hit the stationary balls at about the lowest point of the bat trajectory.     

Bat speed,trajectory, and timing for collegiate baseball batters hitting a stationary ball

The aims of this study were to examine whether batters hit stationary balls at the time of peak speed of the bat head and whether the impact occurs at the lowest point of the bat trajectory. Eight university baseball players hit three balls, each hung with a string; each ball was made of a different material and was different in weight. Bat movement was captured by four 240-Hz infrared cameras and analysed three-dimensionally. Time for peak speed of the bat head varied according to the conditions. When stationary balls of standard weight were used, the bat head was at maximum speed at impact with the ball; then, it decelerated drastically owing to the impact. In contrast, maximum speed was obtained after impact when lightweight stationary balls were used. The time–speed profile of the bat head before impact in the lightweight ball condition was identical with that in the standard weight ball condition. Regardless of conditions, the timing of the lowest point of the bat head was nearly identical for each batter and most participants hit the stationary balls at about the lowest point of the bat trajectory     

Normative feedback effects on learning a timing task

This study investigated the influence of normative feedback on learning a sequential timing task. In addition to feedback about their performance per trial, two groups of participants received bogus normative feedback about a peer group's average block-to-block improvement after each block of 10 trials. Scores indicated either greater (better group) or less (worse group) than the average improvement, respectively. On the transfer test 1 day later which required producing novel absolute movement times, the better group demonstrated more effective learning than the worse group. These findings add to the mounting evidence that motivational factors affect motor skill learning.     

Object Rotation Effects on the Timing of a Hitting Action

Abstract

We investigated how perturbing optical information affects the guidance of an unfolding hitting action. Using monocular and binocular vision, six participants were required to hit a rectangular foam object, released from two different heights, under four different approach conditions, two with object rotation (to perturb the viewed surface area) and two without. Participants made more misses under monocular conditions, and the presence of rotation had a significant effect on the duration between the arm's peak velocity and its contact with the object. We conclude that binocular information contributes to the timing of interceptive tasks. In addition, the guidance of interceptive actions does not appear to be based solely on object expansion information picked up from the viewed surface area.     

Visual illusions and the control of ball placement in goal-directed hitting

When hitting kicking, or throwing balls at targets, online control in the target area is impossible. We assumed this lack of late corrections in the target area would induce an effect of a single-winged Müller-Lyer illusion on ball placement. After extensive practice in hitting balls to different landing locations, participants (N = 9) had to hit a ball to a distant target specified by the vertex of a single-winged Müller-Lyer configuration. Impact velocity was not significantly "tricked" by the pictorial illusion, suggesting that, even when late corrections in the target area are absent, some motor behaviors are not susceptible to the influence of the visual environment surrounding the target.     

Analysis of the 5 iron golf swing when hitting for maximum distance

Most previous research on golf swing mechanics has focused on the driver club. The aim of this study was to identify the kinematic factors that contribute to greater hitting distance when using the 5 iron club. Three-dimensional marker coordinate data were collected (250 Hz) to calculate joint kinematics at eight key swing events, while a swing analyser measured club swing and ball launch characteristics. Thirty male participants were assigned to one of two groups, based on their ball launch speed (high: 52.9 ± 2.1 m · s(-1); low: 39.9 ± 5.2 m · s(-1)). Statistical analyses were used to identify variables that differed significantly between the two groups. Results showed significant differences were evident between the two groups for club face impact point and a number of joint angles and angular velocities, with greater shoulder flexion and less left shoulder internal rotation in the backswing, greater extension angular velocity in both shoulders at early downswing, greater left shoulder adduction angular velocity at ball contact, greater hip joint movement and X Factor angle during the downswing, and greater left elbow extension early in the downswing appearing to contribute to greater hitting distance with the 5 iron club.     

Effects of modeled auditory information on a sequential timing task

The purposes of the present experiment were to determine (a) whether an auditory model enhanced relative or absolute timing, (b) the extent to which the reduced frequency presentation of the auditory model resulted in enhanced retention, and (c) the degree to which executing the timing sequence was independent of the role of the effectors in carrying out the movement sequence. Participants (N = 45) were asked to alternately press two keys on a computer keyboard in an attempt to match the goal intervals presented on the computer monitor. Groups differed in terms of the frequency with which an auditory model (100, 50, or 0%) was presented. The results indicated that the auditory model (100% or 50% groups) enhanced relative timing performance and learning but not the learning of absolute timing. In addition, the 50% group did not appear to become dependent on the auditory model. However, significant decrements in performance were seen for the 100% group when the model was withdrawn. Last, participants were able to execute the timing sequences equally well when they reversed the hand used to execute the timing sequence. This was interpreted as strong evidence for the effector independence (Schmidt, 1975, 1988) and modularity of the timing sequence (Keele, Davidson, & Hayes, 1998).     

Effects of repeated retention tests on learning a single timing task

The purpose of the present study was to investigate the possibility that administering an initial retention test would influence any subsequent retention tests administered to the same participants. Participants performed 40 practice trials of a four-segment key-pressing task with a movement time goal of 925 ms. Participants were then administered either two retention tests (Day 1-Day 1 group, 10 min and 20 min after practice; Day 1-Day 2 group, 10 min and 24 hr after practice; Day 2-Day 2 group, 23 hr 50 min and 24 hr after practice) or one retention test (Day 1-Control group, 20 min after practice; Day 2-Control group, 24 hr after practice). The first test had a deleterious effect on performing the second test for the Day 2-Day 2 group, which would be expected if the task representation was updated and re-encoded at the time of recall using diminished information. This finding suggests that researchers should be cautious about using repeated retention tests that are administered 1 day after practice. In addition, teachers and coaches should consider administering a test under gamelike conditions following practice of a new technique. Otherwise, performance of the new technique may be degraded or perturbed at the time of later performances.     

The effects of baseball bat mass properties on swing mechanics,ground reaction forces,and swing timing

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.     

Effects of strategy use on children's motor performance in a continuous timing task

The purposes of this study were to associate age-related performance deficits in children with the use of recall strategies and to determine whether children who performed poorly in cycling would benefit from learning a recall strategy. In Experiment 1, 18 younger children (ages 5-7years) and 18 older children (ages 8-10 years) were asked to recall selected pedaling cadences. The majority of the older children used strategies and performed with less error than the younger children. In Experiment 2, children with a high number of errors in Experiment 1 were assigned to an experimental or a control group. The children in the experimental group were taught to use a specific recall strategy. The results showed that children who received the instruction in strategy use improved their performance.     

The effects of mid-flight whole-body and trunk rotation on landing mechanics: implications for anterior cruciate ligament injuries

ABSTRACT

The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen’s dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen’s dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen’s dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries.     

体育专业大学生的心理旋转能力

测定了体育专业大学生的反应时、智商和心理旋转能力。研究结果显示：(1)体育专业大学生的反应时与心理旋转能力之间存在显著相关；(2)体育专业大学生心理旋转能力与智力相关不显著；(3)体育专业大学生心理旋转能力存在年级、性别差异；(4)体育专业大学生对不同角度、不同方向材料的心理旋转能力存在显著差异。     

Coincidence timing of a tennis stroke: effects of age, skill level, gender, stimulus velocity, and attention demand

Participants (N = 162, ages 10-15 years) performed a tennis stroke in a coincidence-timing task. Major results were: (a) performance improved mainly between the ages of 10-13 years; (b) skill differences were reflected by variable error (VE); (c) boys were lower than girls for VE and absolute error; (d) high stimulus velocity was related to low VE and late responding. Results concerning response organization favored explanations based on ecological perspectives rather than information processingperspectives. However, it is premature to disregard the potential role of programming. The view is supported that a continuous process of coupling perceptual and motor responses coordinates control of response timing. These cognitive processes appear to be: (a) refined with practice; (b) sensitive to differences in age, skill, and gender; and (c) adaptable to changes in environmental demands.     

再论体育社会学的性质与对象

自20世纪80年代体育社会学在我国兴起以来，学者们对其学科性质和研究对象做了许多有益的探索，对促进学科建设乃至体育社会学在我国的发展做出了重要贡献。但是，作为一门学科，第二次世界大战后开始形成的体育社会学历史尚短，不能和一些较为成熟的学科相比，它的学科理论基础、学科目标、学科性质、研究对象、方法、领域、模式、概念等一系列基本问题仍处在探索和发展之中。本文的命题正是在这个意义上的进一步探索。     

略论动作系统的演化

从动作系统耗散结构特征和动态系统属性的角度,对动作系统的结构,动作系统演化的动力,演化形式及演化的控制问题进行了探讨。旨为发展动作技术优化理论并为动作技术分析提供依据。     

Biomechanics and visual-motor control: how it has, is, and will be used to reveal the secrets of hitting a cricket ball

Cricket batting is an incredibly complex task which requires the coordination of full-body movements to successfully hit a fast moving ball. Biomechanical studies on batting have helped to shed light on how this intricate skill may be performed, yet the many different techniques exhibited by batters make the systematic examination of batting difficult. This review seeks to critically evaluate the existing literature examining cricket batting, but doing so by exploring the strong but often neglected relationship between biomechanics and visual-motor control. In three separate sections, the paper seeks to address (i) the different theories of motor control which may help to explain how skilled batters can hit a ball, (ii) strategies used by batters to overcome the (at times excessive) temporal constraints, and (iii) an interpretation from a visual-motor perspective of the prevailing biomechanical data on batting.     

Influence of pelvis rotation styles on baseball pitching mechanics

Efficient, sequential timing is essential for upper level pitching. Interestingly, pitchers vary considerably in timing related elements of pitching style including pelvis rotation, arm cocking, stride leg behaviour, and pitch delivery time. The purpose of this study was to determine whether relationships exist among these elements by examining the overall style of pitchers exhibiting different pelvis rotation patterns. Pitching styles were defined by pelvis orientation at the instant of stride foot contact. Pitchers demonstrating a pelvis orientation greater than 30 degrees were designated as 'early rotators', while pitchers demonstrating a pelvis orientation less than 30 degrees were designated as 'late rotators'. Kinematic and temporal differences were associated with the two styles. During the arm cocking phase, early rotators showed significantly greater shoulder external rotation at the instant of stride foot contact, earlier occurrence of maximum pelvis rotation angular velocity, and shorter time taken to complete the phase. However, by the instant of maximum shoulder external rotation, early and late rotators appeared remarkably similar as no significant difference occurred in pelvis and arm orientations. Therefore, it appears that early and late rotators used different methods to achieve similar results, including throwing velocity. Significant differences in throwing arm kinetics were also found for 10 of the 11 measures in the study. As the pelvis assumed a more open position at stride foot contact, maximum kinetic values were found to both decrease in magnitude and occur at an earlier time within the pitch.     

Changes in the perception of action possibilities while climbing to fatigue on a climbing wall

Abstract

In two experiments we examined changes in the perception of action possibilities as a function of exertion. In Experiment 1, participants repeatedly climbed on a climbing wall in a series of trials that progressively increased in number to 10 trials, resulting in increased exertion. Before and during climbing, the participants judged their maximum reaching height and perceived exertion. On a separate day, participants climbed another 10 trials while performing actual maximum reaches. Higher perceived exertion was associated with decreases in perceived maximum reach while the actual reaches did not decrease. However, the perceptual changes occurred early during task execution when the participants were not yet fatigued. When exertion set in, neither perceived nor actual maximum reaching appeared to be affected. In Experiment 2, we included exhaustion trials. The findings replicated the early changes in perception observed in Experiment 1, which may be explained by hands-on experience with the task. Furthermore, while climbing to exhaustion, perceptual judgements largely changed in keeping with changes in the actual maximum reach. Thus, there appeared to be a functional relationship between participants' actual action capabilities, rather than their state of physical fatigue per se, and perceived action possibilities.     

Changes in the perception of action possibilities while climbing to fatigue on a climbing wall

In two experiments we examined changes in the perception of action possibilities as a function of exertion. In Experiment 1, participants repeatedly climbed on a climbing wall in a series of trials that progressively increased in number to 10 trials, resulting in increased exertion. Before and during climbing, the participants judged their maximum reaching height and perceived exertion. On a separate day, participants climbed another 10 trials while performing actual maximum reaches. Higher perceived exertion was associated with decreases in perceived maximum reach while the actual reaches did not decrease. However, the perceptual changes occurred early during task execution when the participants were not yet fatigued. When exertion set in, neither perceived nor actual maximum reaching appeared to be affected. In Experiment 2, we included exhaustion trials. The findings replicated the early changes in perception observed in Experiment 1, which may be explained by hands-on experience with the task. Furthermore, while climbing to exhaustion, perceptual judgements largely changed in keeping with changes in the actual maximum reach. Thus, there appeared to be a functional relationship between participants' actual action capabilities, rather than their state of physical fatigue per se, and perceived action possibilities.