INERTIAL AND VIBRATIONAL CHARACTERISTICS OF SOFTBALL AND BASEBALL BATS: RESEARCH AND DESIGN IMPLICATIONS

The design of baseball and softball bats has been an ongoing process since the inception of the game in the early 19th century. Until the early 1970's, the only material to be used was wood and the potential for design improvements was limited because they involved changing the physical dimensions of the bat. Also, most of the changes were initiated by the player and were carried out by local craftsmen in wood shops. With the introduction of hollow-wall aluminum bats in the 1970's and other metal alloys as well as composite materials since then, the potential for applying relevant mechanical principles to improve the performance characteristics of bats has improved dramatically. When developing or evaluating a design feature, the following factors must be considered: (1) how is the bat swung and how forces are transmitted to the bat during the swing, (2) what are the constraints resulting from rules in the particular sport, and (3) what mechanical properties are relevant. Baseball and softball batting is a two-handed sidearm striking skill with the bat held at one hand and swung as a physical pendulum as the batter attempts to impart maximum velocity to the impacted ball in the desired direction by generating maximum linear velocity of the impacting part of the bat to the ball. The motion of the bat is predominantly in the horizontal plane and the rotation axis ranges from .15 to.20 m off the knob end of the bat toward the hitter’s body during the swing. Maximum bat velocity is usually achieved from .01 to .05 s prior to impact. The rules regarding baseball bat characteristics are different from those regarding softball bats. Also, rules are different for different genders and different levels of play. Until recently, most rules related to the bat’s composition, dimensions, and weight; however, a recent rule setting an upper limit on the coefficient of restitution (Bat Performance Factor) for bats at different levels and types of play is having a tremendous impact on the direction of bat design activity. Several inertial and vibrational properties of the bat are relevant to its effective use: (1) mass, (2) moment of inertia, (3) coefficient of restitution, (4) vibration frequency and node locations, and (5) center of percussion location. Mass and moment of inertia determine the amount of effort required to swing the bat while the latter three factors largely determine the bat’s effectiveness during impact in transferring maximum energy to the bat while transferring minimum energy to the human. When considering recent research and development activity and recent rules changes limiting the coefficient of restitution of baseball and softball bats, future improvements in bat design will most likely be related to coupling the bat’s flexibility with the batter’s swing

RELATIVE EFFECTS OF WARM-LIP WITH UNDERWEIGHT, OVERWEIGHT, AND STANDARD WEIGHT BATS ON BAT VELOCITY AND SEGMENTAL MOVEMENT

The purpose of this investigation was to compare the effects of warming up with bats of varying weight on pre-impact bat linear velocity and on the timing and extent of segmental movement during the baseball swing, Sixteen varsity high school baseball players volunteered as subjects for the study The subjects were videotaped from overhead while hitting wiffle balls off of a hitting tee following each of three standardized warm-up routines using bats of varying weight Each subject performed 6-10 swings following each warm-up condition with the three best swings per condition selected for analysis, Pre-impact velocity of the impact point of the bat (measured electronically) and the timing and extent of segmental movements were compared, No significant intergroup differences for either pre-impact bat linear velocity or the segmental kinematic variables were found

EFFECTS OF IMPACT LOCATION ON SOFTBALL BAT VIBRATIONS AND DISCOMFORT

Studies examining the effects of interior loading on the location of the center of percussion (COP) of aluminium softball and baseball bats 'have resulted in recommended procedures for the systematic displacement 'of the COP. While the effect of distal displacement of the COP has been shown to improve pat performance, interior loading procedures have also been shown to dramatically change fundamental frequency and distance between the distal node of the fundamental mode and COP. Previous research with softball bats has shown that the COP a-d node of the fundamental mode are the preferred areas for ball-bat impact when they are relatively close together (less than 2 cm) with no significant difference between the two impact sites regarding preference. When these two parameters are farther apart, one site may be preferred over the other, as has been suggested in a recent study with tennis racquets. This study compared vibrational characteristics d perceptions of discomfort resulting from impacts on the Center of Percussion (COP) and fundamental vibrational node of bats with varying COP-node distances. Seventeen adult skilled slow-pitch softball players (9 females, 8 males) aged 25-40 years held each of four aluminium softball bats while they were impacted at the following locations by softballs at an approximate speed of 26 m/s: COP, distal node of fundamental mode, and midway between these two points. Results of a questionnaire regarding annoyance and discomfort were correlated with mechanical characteristics and vibrational characteristics associated with each impact location. The data indicated that: (1) discomfort was directly related to the degree of excitation of both the fundamental and first overtone vibrational modes, which was directly related to nodeimpact distance; (2) bats with higher fundamental frequencies &ere more comfortable than bats with lower fundamental frequencies: and (31 with bats having large fundamental node-COP distances (greater' than 9 cm) COP impacts are significantly less comfortable than impacts on the node

BAT LOADING STRATEGIES

The effects of adding mass at different locations along the longitudinal axis of a softball bat on the effective hitting area were compared. Successive loads were added to the exterior of a standard, commercially available aluminum bat (length = 86.7 cm, mass = 741 g) in increments of 93.7 g. The loads were placed at the following sites: (1) at the knob end, (2) at the junction of the bat handle and knob end, (3) at a point 12 cm from the knob end, (4) at a point 16.8 cm from the knob end, (5) at the center of mass, (6) at the center of percussion, and (7) at the barrel end. The second and third points were selected to coincide with the swing axis and impact reaction axis, respectively. The effects of each of these loading conditions on each of the following mechanical parameters were determined theoretically, by physical pendulum testing, and empirically by impact testing: (1) moment of inertia about the swing axis, (I1), (2) distance from the impact reaction axis to the center of percussion, and (3) slope of the impact reaction impulse as a function of impact location. The latter two variables were used to determine the effective hitting area of the bat. Results from impact testing were consistent with theoretical expectations and with results from the physical pendulum tests. Knob end loading had the greatest effect on displacement of the effective hitting area toward the barrel end of the bat and on enlarging the effective hitting area. Loading at the impact reaction axis and center of percussion had no effect on the effective hitting area. Loading at the barrel end of the bat substantially moved the effective hitting area toward the barrel end of the bat, but also caused a large increase in I1

PHYSICS OF SPORTS: AN INTERACTIVE VIDEODISC FOR ANALYZING THE MOTION OF ATHLETES

Physics teachers have long used visual media to show how principles of physics are applied to everyday events. Visual presentation seems to motivate the students and improve their understanding of the concepts being taught. The approach taken in most of these presentations has been a qualitative one. Few quantitative visual presentations have been used in instructional settings, particularly in the laboratory, with some notable exceptions (Super-8 Film Series for Project Physics, 1971). The difficulty of working with films and slides limits the amount of quantitative information that can be acquired from them

An investigation of equivalent radii for P₃ calculations in strong absorbers

Call number: LD2668 .T4 1964 N74Master of Scienc

N = 1 Designs: The Failure of ANOVA-Based Tests

↵TOOTHAKER, LARRY E. Professor, Department of Psychology, University of Oklahoma, Norman, OK 73019.Specializations: Randomization tests, individual comparisons, robustness.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Temporal, Spatial, and Genomic Analyses of Enterobacteriaceae Clinical Antimicrobial Resistance in Companion Animals Reveals Phenotypes and Genotypes of One Health Concern

BackgroundAntimicrobial resistance (AMR) is a globally important one health threat. The impact of resistant infections on companion animals, and the potential public health implications of such infections, has not been widely explored, largely due to an absence of structured population-level data.ObjectivesWe aimed to efficiently capture and repurpose antimicrobial susceptibility test (AST) results data from several veterinary diagnostic laboratories (VDLs) across the United Kingdom to facilitate national companion animal clinical AMR surveillance. We also sought to harness and genotypically characterize isolates of potential AMR importance from these laboratories.MethodsWe summarized AST results for 29,330 canine and 8,279 feline Enterobacteriaceae isolates originating from companion animal clinical practice, performed between April 2016 and July 2018 from four VDLs, with submissions from 2,237 United Kingdom veterinary practice sites.ResultsEscherichia coli (E. coli) was the most commonly isolated Enterobacteriaceae in dogs (69.4% of AST results, 95% confidence interval, CI, 68.7–70.0) and cats (90.5%, CI 89.8–91.3). Multi-drug resistance was reported in 14.1% (CI 13.5–14.8) of canine and 12.0% (CI 11.1–12.9) of feline E. coli isolates. Referral practices were associated with increased E. coli 3rd generation ≤ cephalosporin resistance odds (dogs: odds ratio 2.0, CI 1.2–3.4). We selected 95 E. coli isolates for whole genome analyses, of which seven belonged to sequence type 131, also carrying the plasmid-associated extended spectrum β-lactamase gene blaCTX–M–15. The plasmid-mediated colistin resistance gene mcr-9 was also identified for the first time in companion animals.ConclusionsLinking clinical AMR data with genotypic characterization represents an efficient means of identifying important resistance trends in companion animals on a national scale.</sec

Multisite reliability of MR-based functional connectivity

Recent years have witnessed an increasing number of multisite MRI functional connectivity (fcMRI) studies. While multisite studies are an efficient way to speed up data collection and increase sample sizes, especially for rare clinical populations, any effects of site or MRI scanner could ultimately limit power and weaken results. Little data exists on the stability of functional connectivity measurements across sites and sessions. In this study, we assess the influence of site and session on resting state functional connectivity measurements in a healthy cohort of traveling subjects (8 subjects scanned twice at each of 8 sites) scanned as part of the North American Prodrome Longitudinal Study (NAPLS). Reliability was investigated in three types of connectivity analyses: (1) seed-based connectivity with posterior cingulate cortex (PCC), right motor cortex (RMC), and left thalamus (LT) as seeds; (2) the intrinsic connectivity distribution (ICD), a voxel-wise connectivity measure; and (3) matrix connectivity, a whole-brain, atlas-based approach assessing connectivity between nodes. Contributions to variability in connectivity due to subject, site, and day-of-scan were quantified and used to assess between-session (test-retest) reliability in accordance with Generalizability Theory. Overall, no major site, scanner manufacturer, or day-of-scan effects were found for the univariate connectivity analyses; instead, subject effects dominated relative to the other measured factors. However, summaries of voxel-wise connectivity were found to be sensitive to site and scanner manufacturer effects. For all connectivity measures, although subject variance was three times the site variance, the residual represented 60–80% of the variance, indicating that connectivity differed greatly from scan to scan independent of any of the measured factors (i.e., subject, site, and day-of-scan). Thus, for a single 5 min scan, reliability across connectivity measures was poor (ICC=0.07–0.17), but increases with increasing scan duration (ICC=0.21–0.36 at 25 min). The limited effects of site and scanner manufacturer support the use of multisite studies, such as NAPLS, as a viable means of collecting data on rare populations and increasing power in univariate functional connectivity studies. However, the results indicate that aggregation of fcMRI data across longer scan durations is necessary to increase the reliability of connectivity estimates at the single-subject level

ABM Clinical Protocol #18: Use of Antidepressants in Breastfeeding Mothers

A central goal of The Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient