Field and laboratory measurements of softball player swing speed and bat performance

The swing speed of the bat is one of the most important factors affecting the hit-ball speed. Most field studies tend to focus on measuring ball speed, which is easier to measure and quantify than bat speed. For this reason, relatively little data exist describing bat motion in field conditions. The following describes a relatively large swing speed field study involving bats of the same model with nearly constant weight and varying inertia. The study was conducted using right-handed batters on a regulation outdoor field with a live pitcher. Swing speed was measured by tracking markers on the bat with two high-speed video cameras so that the bat markers could be traced in three-dimensional space. The ball motion was tracked using the same high-speed video cameras and a three-dimensional Doppler radar system. Bat swing speed was observed to be proportional to the batter skill level and the normalised swing speed increased with decreasing bat inertia. The bat centre of rotation during impact was close to the knob of the bat. The bats were tested under controlled laboratory conditions using a standardised performance test. The field and laboratory results showed good agreement including the hit-ball speed and the subtle effect of bat inertia on the maximum performance location. The vibrational response of the bats was considered using modal analysis. The maximum performance location was correlated with the node of the first vibrational mode.     

A pitcher injury risk assessment study analyzing composite,titanium, aluminum and wood softball bat performance

Abstract

Over the past few years, there has been a significant increase in the performance of softball bats from the Olympics down to the recreational level. It is theorized that the introduction of composite-based material bats has been the largest contributor to the increase in batted-ball performance, which directly corresponds to a decrease in available pitcher reaction time that can lead to an increase in injury potential. To test this theory, a controlled field-test study comparing all of the different bat model types currently available was conducted. The performance of ten bat model types; two composite-based, two titanium-based, two aluminum-based multi-wall, two aluminum-based single-wall and two wood-based bats were measured using 1686 N/0.64 cm (379 lbs/0.25”) compression softballs in order to calculate available pitcher reaction times when using a specific bat model type. Over 1000 Batted-ball velocity measurements were analyzed using two calibrated radar devices and five experienced test subjects. The results of this study indicate that when titanium-based or composite-based softball bat performance results are compared to published safety studies in the sports of softball and baseball, available pitcher reaction times are unsafe, which can lead to a higher injury risk potential. The significance of this research is to provide experimental field-test data on the possible safety risks to pitchers that can be used to reduce the injury potential and promote safety awareness in the sport of softball.     

The influence of moment of inertia on baseball/softball bat swing speed

The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent, the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets, balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured speeds, from 22 to 31 m s⁻¹, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest the importance of additional degrees of freedom in determining swing speed.     

A comparative study of baseball bat performance

The results of a comparative study of five aluminum and one wood baseball bats are presented. The study includes an analysis of field data, high-speed laboratory testing, and modal analysis. It is found that field performance is strongly correlated with the ball–bat coefficient of restitution (BBCOR) and only weakly correlated with other parameters of the bat, suggesting that the BBCOR is the primary feature of a bat that determines its field performance. It is further found that the instantaneous rotation axis of the bat at the moment of impact is very close to the knob of the bat and that the rotational velocity varies inversely with the moment of inertia of the bat about the knob. A swing speed formula is derived from the field data and the limits of its validity are discussed. The field and laboratory measurements of the collision efficiency are generally in good agreement, as expected on theoretical grounds. Finally, the BBCOR is strongly correlated with the frequency of the lowest hoop mode of the hollow bats, as predicted by models of the trampoline effect.     

Describing the plastic deformation of aluminium softball bats

Hollow aluminium bats were introduced over 30 years ago to provide improved durability over wooden bats. Since their introduction, however, interest in hollow bats has focused almost exclusively around their hitting performance. The aim of this study was to take advantage of the progress that has been made in predicting bat performance using finite elements and apply it to describe bat durability. Accordingly, the plastic deformation from a ball impact of a single-wall aluminum bat was numerically modelled. The bat deformation from the finite-element analysis was then compared with experiment using a high-speed bat test machine. The ball was modelled as an isotropic, homogeneous, viscoelastic sphere. The viscoelastic parameters of the ball model were found from instrumented, high-speed, rigid-wall ball impacts. The rigid-wall ball impacts were modelled numerically and showed good agreement with the experimentally obtained response. The strain response of the combined bat-ball model was verified with a strain-gauged bat at intermediate ball impact speeds in the elastic range. The strain response of the bat-ball model exhibited positive correlation with the experimental measurements. High-speed bat-ball impacts were performed experimentally and simulated numerically at increasing impact speeds which induced correspondingly increased dent sizes in the bat. The plastic deformation from the numerical model found good agreement with experiment provided the aluminium work hardening and strain rate effects were appropriately described. The inclusion of strain rate effects was shown to have a significant effect on the bat deformations produced in the finite-element simulations. They also helped explain the existence of high bat stresses found in many performance models.     

An impact analysis of a flexible bat using an iterative solver.

Although technology has now infiltrated and prompted evolution in most mass participation sports, the advances in bat technology in such sports as baseball and cricket have been relatively minor. In this study, we used a simple finite element modelling approach to try to shed new light upon the underlying mechanics of the bat-ball impact, with a view to the future optimization of bat design. The analysis of a flexible bat showed that the point of impact that produced the maximum post-impact ball velocity was a function of the bat's vibrational properties and was not necessarily at the centre of percussion. The details of the analysis agreed well with traditional Hertzian impact theory, and broadly with empirical data. An inspection of the relative modal contributions to the deformations during impact also showed that the position of the node of the first flexure mode was important. In conclusion, considerable importance should be attached to the bat's vibrational properties in future design and analysis.     

Assessment of the power performance of racing cyclists

A 30-s 'all-out' power protocol was studied in four groups of racing cyclists including internationals (n = 8), Category 1 (n = 10), Category 2 (n = 15) and Category 3 (n = 11). Following warm-up each subject completed five trials interspersed by 3 min of low intensity exercise on an ergowheel racing cycle ergometry system at a power output of 15 W kg-1 body weight, generated at 130 rev min-1. Temporal indices of performance included delay time (DT) to achieve the power criterion, total time (TT) of the maintenance of the power criterion and the ratio of TT/DT. 'Explosive' leg strength was assessed from a vertical jump. The results indicated that international and Category 1 cyclists had lower DT (2.2 +/- 0.1 s and 2.1 +/- 0.0 s, respectively; P less than 0.05), higher TT (28.1 +/- 0.7 s and 27.0 +/- 0.7 s, respectively; P less than 0.05) and elevated TT/DT (12.8 and 12.9, respectively; P less than 0.01). 'Explosive' leg strength was also higher (P less than 0.05) in the internationals than in the other groups of cyclists. The protocol provides a sport-related method for the assessment of short term endurance performance ability in racing cyclists which may be of value in identifying the anaerobic capability of individual cyclists.     

Assessment of the power performance of racing cyclists

A 30‐s ‘all‐out’ power protocol was studied in four groups of racing cyclists including internationals (n = 8), Category 1 (n = 10), Category 2 (n = 15) and Category 3 (n = 11). Following warm‐up each subject completed five trials interspersed by 3 min of low intensity exercise on an ergowheel racing cycle ergometry system at a power output of 15 W kg^–1 body weight, generated at 130 rev min^–1. Temporal indices of performance included delay time (DT) to achieve the power criterion, total time (TT) of the maintenance of the power criterion and the ratio of TT/DT. ‘Explosive’ leg strength was assessed from a vertical jump. The results indicated that international and Category 1 cyclists had lower DT (2.2 ± 0.1s and 2.1 +0.0s, respectively; P<0.05), higher TT (28.1 ±0.7s and 27.0+0.7s, respectively; P<0.05) and elevated TT/DT (12.8 and 12.9, respectively; P<0.01). ‘Explosive’ leg strength was also higher (P<0.05) in the internationals than in the other groups of cyclists. The protocol provides a sport‐related method for the assessment of short term endurance performance ability in racing cyclists which may be of value in identifying the anaerobic capability of individual cyclists.     

Assessment of ice hockey performance in real-game conditions

Abstract

The aim of this study was to adapt a performance measurement tool, the Team Sport Assessment Procedure (TSAP), to ice hockey during match-play. In addition to the six categories included in the original observational procedure, the ice hockey TSAP contained four new categories. Twelve Pee-Wee ice hockey matches were video-recorded during a regional championship tournament. The game play of 103 of the 11- to 12-year-old players was then analysed on video by three trained observers, based on all 10 ice hockey TSAP categories. The observational data were thereafter used to compute, for each player, a “volume of play per minute” and an efficiency index. Finally, volume of play per minute and the efficiency index were combined to obtain a composite score, the TSAP performance score. Additional measurements for each player were playing time during the observed matches, coaches’ assessments (dominant, good, less decisive), and player tournament statistics (number of points, based on assists and goals). The mean TSAP performance score was substantially higher for players rated by their coaches as dominant and for players who accumulated more than one tournament point, findings that provide evidence of the validity of the TSAP measure. In inter-observer reliability analyses of TSAP observational data provided by the trained observersfrom video recordings, the level of agreement between each pair of observers was 80–82%. Reliability correlations over a series of three matches (r=0.26, 0.59, and 0.16 respectively) showed that the TSAP performance score was relatively unstable. Ice hockey coaches may use this adapted Team Sport Assessment Procedure to better understand the offensive implication of each player in a given match, since the 10 observational variables provide more extensive information on performance than traditional statistical measures. Due to low performance stability of the TSAP performance score, coaches ought to use the observational assessment data for the formative rather than the summative assessment of their players unless they cumulate information over a series of several matches. Formative assessment can be conducted either during training camps or even during the regular season.     

项群比较视角下柔力球套路美与难的特征及创新启示

柔力球套路之美,兼取自由体操健体之美,武术套路技击艺术优之美,艺术体操律动之美。其动作难度主要反映在跳跃、平衡、转体三类动作,并且套路动作明显表现出复合多样性,套路动作连接呈现出明显的个性特征。可采用融合创新法、移植创新法、类比创新法和动作音乐合拍法对柔力球项目进行创新。在创编柔力球新套路时,应把握新套路的基本特征,提升音乐鉴赏能力,并注重自我创编能力的培养。     

Evaluation of wireless bat swing speed sensors

Batter swing speed is an important parameter in understanding the performance of baseball and softball players. A number of swing speed sensors have recently been introduced and are commercially available. The aim of this study was to compare three wireless swing sensors with high speed video. Swing speed from high speed video was measured by differentiating the position coordinates of tracking markers on the bat barrel. On average, the wireless bat swing sensors reported speeds 8% slower than that found from video tracking. The agreement was better at low swing speeds, suggesting that the current generation of wireless sensors is best suited for developing players. Spatial measures, such as swing angle, were not in good agreement with video tracking.     

十运会与九运会垒球决赛技术统计比较

通过对参加十运会女子垒球决赛的11支运动队的技术进行统计,并与九运会前8名运动队的技术统计进行比较,结果发现:我国女子垒球运动员的击球技术总体水平有明显提高;各队的防守水平较九运会有所下降;受规则修改的影响,投手水平呈下降趋势,优秀投手在比赛中的作用被削弱。建议继续加强击球、防守能力的训练,提高运动员对赛场环境、比赛气氛的适应能力;创新投手训练方法,尽快培养优秀投手。     

Assessment of decision-making performance and in-game physical exertion of Australian football umpires

Abstract

The aim of this study is to investigate the effects of in-game physical exertion on decision-making performance of Australian football umpires. Fifteen Australian football umpires (M_age = 36, s = 13.5 years; M_{games umpired} = 235.2, s = 151.3) volunteered to participate in the study. During five competitive Australian football pre-season games, measures of in-game physical exertion (blood lactate levels, global positioning system [GPS]) and decision-making performance (video-based test) were obtained. There were no significant correlations between physical exertion in a particular quarter and decision-making performance in either the same quarter or any other quarter. Video-based decision-making performance was effected by time in game χ²(3) = 24.24, P = 0.001, with Quarter 4 performance significantly better than both Quarter 2 and Quarter 3. In-game physical exertion (blood lactate) significantly decreased over the course of the game χ²(3) = 11.58, P = 0.009. Results indicate no definable link between in-game physical exertion and decision-making performance. It is, however, presumed that decision-making performance may be affected by the time or context of the game. Future research is warranted to explore the relationship between physical exertion and decision-making performance to potentially inform Australian football umpire training programmes that replicate in-game physical and decision-making demands.     

Measuring intermittent exercise performance using shuttle running

Abstract

The aim of this study was to include self-paced exercise within a modified Loughborough Intermittent Shuttle Test (LIST-P) in order to quantify key performance variables not possible with prescribed workloads. Sixteen male games players performed two trials of the LIST-P, at least 7 days apart. The LIST-P incorporates 4 × 15-min blocks of “prescribed-pace” activity (participants exercise in time to audible signals) followed by 2 × 15-min blocks of “self-paced” running (no audible signals). Distances covered and mean speeds were monitored during self-paced exercise. Total distance covered (12.54 ± 0.45 km vs. 12.64 ± 0.32 km; P = 0.10) and mean speed (8.37 ± 0.31 km ? h^?1 vs. 8.44 ± 0.22 km ? h^?1; P = 0.10) was similar between trials. Other indices also showed the test to be reliable (Pearson’s correlation = 0.89 and 0.90 (P < 0.01), total distance and mean speed, respectively; intraclass correlation coefficient = 0.88 and 0.88 (P < 0.01); standard error of measurement = ±0.13 km and ±0.09 km ? h^?1; coefficient of variation (CV) = 1.7% and 1.7%; ratio limits of agreement = 1.00 */÷1.03 and 1.01 */÷1.04). Sprint time was also similar between trials (2.60 ± 0.19 s vs. 2.64 ± 0.23 s; P = 0.29). Incorporating self-paced exercise within an established intermittent shuttle running test appears to be a sensitive means of quantifying key performance variables for multiple-sprint sports research.     

Predicting biathlon shooting performance using machine learning

Shooting in biathlon competitions substantially influences final rankings, but the predictability of hits and misses is unknown. The aims of the current study were A) to explore factors influencing biathlon shooting performance and B) to predict future hits and misses. We explored data from 118,300 shots from 4 seasons and trained various machine learning models before predicting 34,340 future shots (in the subsequent season). A) Lower hit rates were discovered in the sprint and pursuit disciplines compared to individual and mass start (P < 0.01, h = 0.14), in standing compared to prone shooting (P < 0.01, h = 0.15) and in the 1^st prone and 5^th standing shot (P < 0.01, h = 0.08 and P < 0.05, h = 0.05). B) A tree-based boosting model predicted future shots with an area under the ROC curve of 0.62, 95% CI [0.60, 0.63], slightly outperforming a simple logistic regression model and an artificial neural network (P < 0.01). The dominant predictor was an athlete’s preceding mode-specific hit rate, but a high degree of randomness persisted, which complex models could not substantially reduce. Athletes should focus on overall mode-specific hit rates which epitomise shooting skill, while other influences seem minor.     

Assessment of step accuracy using the Consumer Technology Association standard

The purpose of this study was to compare the accuracy of commercially-available physical activity devices when walking and running at various treadmill speeds using CTA 2056: Physical Activity Monitoring for Fitness Wearables: Step Counting, standard by the Consumer Technology Association (CTA). Twenty participants (10 males and 10 females) completed self-paced walking and running protocols on the treadmill for five minutes each. Eight devices (Apple iWatch series 1, Fitbit Surge, Garmin 235, Moto 360, Polar A360, Suunto Spartan Sport, Suunto Spartan Trainer, and TomTom Spark 3) were tested two at a time, one per wrist. Manual step counts were obtained from video to serve as the benchmark. The mean absolute percent error (MAPE) was calculated during walking and running. During walking, three devices: Fitbit Surge (11.20%), Suunto Sport (22.93%), and TomTom (10.11%) and during running, one device, Polar (10.66%), exceeded the CTA suggestion of a MAPE < 10%. The Moto 360 had the lowest MAPE of all devices for both walking and running. The devices tested had higher step accuracy with running than walking, except for the Polar. Overall, the Apple iWatch series 1, Moto 360, Garmin, and Suunto Spartan Trainer met the CTA standard for both walking and running.     

Assessment of energy expenditure in children using the RT3 accelerometer

The aim of this study was to evaluate the utility of the RT3 accelerometer in young children, compare its accuracy with heart rate monitoring, and develop an equation to predict energy expenditure from RT3 output. Forty-two volunteers (mean age 12.2 years, s = 1.1) exercised at two horizontal and graded walking speeds (4 and 6 km.h(-1), 0% grade and 6% grade), and one horizontal running speed (8 km.h(-1), 0% grade), on a treadmill. Energy expenditure and oxygen consumption (VO2) served as the criterion measures. Comparison of RT3 estimates (counts and energy expenditure) demonstrated significant differences at 4, 6, and 8 km.h(-1) on level ground (P < 0.01), while no significant differences were noted between horizontal and graded walking at 4 and 6 km.h(-1). Correlation and regression analyses indicated no advantage of vector magnitude over the vertical plane (X) alone. A strong relationship between RT3 estimates and indirect calorimetry across all speeds was obtained (r = 0.633-0.850, P < 0.01). A child-specific prediction equation (adjusted R2 = 0.753) was derived and cross-validated that offered a valid energy expenditure estimate for walking/running activities. Despite recognized limitations, the RT3 may be a useful tool for the assessment of children's physical activity during walking and running.     

Assessment of energy expenditure in children using the RT3 accelerometer

Abstract

The aim of this study was to evaluate the utility of the RT3 accelerometer in young children, compare its accuracy with heart rate monitoring, and develop an equation to predict energy expenditure from RT3 output. Forty-two volunteers (mean age 12.2 years, s = 1.1) exercised at two horizontal and graded walking speeds (4 and 6 km · h^?1, 0% grade and 6% grade), and one horizontal running speed (8 km · h^?1, 0% grade), on a treadmill. Energy expenditure and oxygen consumption ([Vdot]O₂) served as the criterion measures. Comparison of RT3 estimates (counts and energy expenditure) demonstrated significant differences at 4, 6, and 8 km · h^?1 on level ground (P < 0.01), while no significant differences were noted between horizontal and graded walking at 4 and 6 km · h^?1. Correlation and regression analyses indicated no advantage of vector magnitude over the vertical plane (X) alone. A strong relationship between RT3 estimates and indirect calorimetry across all speeds was obtained (r = 0.633–0.850, P < 0.01). A child-specific prediction equation (adjusted R ² = 0.753) was derived and cross-validated that offered a valid energy expenditure estimate for walking/running activities. Despite recognized limitations, the RT3 may be a useful tool for the assessment of children's physical activity during walking and running.     

Surface hardness of a cricket bat after ‘knock-in’

New cricket bats need to be ‘knocked in’ prior to use, but just what this process does to the surface fibres of the bat is unknown and unquantified. One quantitative measurement of knock-in is the resultant surface hardness of the bat, and this paper describes knock-in tests to determine the surface hardness following differing durations of knock-in. The design of a cricket bat knock-in machine is first described. This takes the form of a cradle in which a cricket bat can be secured horizontally and then traversed at constant speeds in two mutually perpendicular directions while at the same time being struck with constant force by a cricket ball. The traverses are driven by lead screws, the motors of which can be independently switched on or off. The traverse distance can be varied with adjustable limit switches and relays that reverse the direction of rotation of the lead screws when activated. The cricket ball is attached to a rod that is lifted cyclically by a cam against a coil spring extension, and then allowed to fall under that force to impact on the bat surface. The impact (knocking-in) force was measured by a previously calibrated strain gauge attached to the rod holding the cricket ball. By judicious setting of the limit switches, selected areas of the bat surface were continuously knocked in for periods varying from 1 to 4 hours. After knocking in, the surface hardness was measured in accordance with British Standard 373 using a penetrator designed in accordance with the same standard. Analysis of the load/penetration curves shows an increase in surface hardness with knock duration. Photographs of the cell structure of the surface wood, obtained using a scanning electron microscope, show that under knock-in conditions, the wood cells collapse to form a mesh-like hardened layer which increases in hardness with increase in knock-in duration.