Body composition of English Premier League soccer players: Influence of playing position,international status,and ethnicity     

Laura Sutton  Mark Scott  Joanne Wallace  Tom Reilly 《Journal of sports sciences》2013,31(10):1019-1026

Abstract

Body composition is a key consideration in the physical make-up of professional soccer players. The aims of the present study were to determine whether the body composition of professional soccer players varied according to playing position, international status or ethnicity, and to establish which variables best distinguished the soccer players from a reference group. Body composition was assessed using dual-energy X-ray absorptiometry in 64 male professional soccer players. Measured variables included bone mineral density and the relative amounts of lean and fat mass. Data were analysed using analysis of variance and stepwise discriminant function. The soccer players recorded better values than a reference group (n = 24) for all body composition compartments. Percent lean mass and bone mineral density were the variables best able to identify the soccer players (95.5% correctly classified). Differences in body composition were evident between goalkeepers and outfield players, but not between outfield playing positions. No differences were found on the basis of international status. The non-Caucasian players demonstrated significantly lower percent body fat (9.2 ± 2.0%) than the Caucasian players (10.7 ± 1.8%). It was concluded that body composition is important for elite soccer players, but that homogeneity between players at top professional clubs results in little variation between individuals.  相似文献   

Ball launch conditions for skilled golfers using drivers of different lengths in an indoor testing facility     

E. S. Wallace  S. R. Otto  A. Nevill 《Journal of sports sciences》2013,31(7):731-737

Abstract

The displacement of the golf ball struck by a driving club is affected by several player characteristics and equipment parameters and their interrelationships. Some modelling and simulation studies have shown a relationship between shaft length and clubhead speed, supported by a few experimental studies. The aim of the present study was to examine the relationship between driver length and ball launch conditions in an indoor test facility using a ball launch monitor. Nine males considered to be skilled golfers participated in the study. Four driving clubs of total length 117, 119, 124, and 132 cm were assembled from commercially available components and were used to strike golf shots while initial ball velocity, backspin rate, and launch angles were measured. Statistical analysis identified a significant difference in initial launch speed due to club length, a significant difference between participants, but no difference between the trials for a given golfer. A positive trend was noted between backspin and launch angle for all four clubs, and significant inverse associations between initial launch speed and backspin rate and launch angle. However, the combined launch conditions associated with increasing length were not considered optimal, with uncontrolled swingweight and moment of inertia effects considered to be limiting factors.  相似文献   

Determination of the swing technique characteristics and performance outcome relationship in golf driving for low handicap female golfers     

Susan J. Brown  Alan M. Nevill  Stuart A. Monk  Steve R. Otto  W. Scott Selbie  Eric S. Wallace 《Journal of sports sciences》2013,31(14):1483-1491

Abstract

Previous studies on the kinematics of the golf swing have mainly focused on group analysis of male golfers of a wide ability range. In the present study, we investigated gross body kinematics using a novel method of analysis for golf research for a group of low handicap female golfers to provide an understanding of their swing mechanics in relation to performance. Data were collected for the drive swings of 16 golfers using a 12-camera three-dimensional motion capture system and a stereoscopic launch monitor. Analysis of covariance identified three covariates (increased pelvis–thorax differential at the top of the backswing, increased pelvis translation during the backswing, and a decrease in absolute backswing time) as determinants of the variance in clubhead speed (adjusted r ² = 0.965, P < 0.05). A significant correlation was found between left-hand grip strength and clubhead speed (r = 0.54, P < 0.05) and between handicap and clubhead speed (r = ?0.612, P < 0.05). Flexibility measures showed some correlation with clubhead speed; both sitting flexibility tests gave positive correlations (clockwise: r = 0.522, P < 0.05; counterclockwise: r = 0.711, P < 0.01). The results suggest that there is no common driver swing technique for optimal performance in low handicap female golfers, and therefore consideration should be given to individual swing characteristics in future studies.  相似文献   

Positive behavioral contrast,autoshaping, and omission responding in the goldfish (Carassius auratus)     

Sarah W. Bottjer  Stanley R. Scobie  Julia Wallace 《Learning & behavior》1977,5(4):336-342

Two experiments with goldfish were performed to investigate the role of stimulus-reinforcer vs. response-reinforcer relationships in omission training and the role of stimulus localizability in a positive behavioral contrast paradigm. The directed behavior of fish, like that of pigeons and rats in other studies, was greatly influenced by positive stimulus-reinforcer correlations, as evidenced by maintained contacts of a signal for food, even though such responses terminated the signal and cancelled reinforcement delivery. Goldfish exhibited positive behavioral contrast when the signals for reinforcement and nonreinforcement were displayed directly on the response key, but no contrast was observed when variations in a diffuse houselight stimulus were used as signals for reinforcement or nonreinforcement. Analysis of sequential-trial data yielded effects analogous to Pavlovian positive and negative induction. Theoretical and methodological problems were briefly considered.  相似文献   

Behavior Problems and Social Skills in Preschool Children: Parent-Teacher Agreement and Relations with Classroom Observations     

Adam Winsler  Gregory L. Wallace 《Early education and development》2002,13(1):41-58

The goals of the present investigation were to provide basic psychometric information about the use of the Preschool and Kindergarten Behavior Scales (PKBS: Merrill, 1994) with a sample of normally-developing preschool children, to assess agreement between parent and teacher ratings of children on this instrument, and to assess concurrent, criterion-related validity of these instruments in terms of their relations with observations of children's behavior in the classroom. Parents and teachers of 47 preschool children completed the scales and these children were observed naturalistically in the classroom setting. Overall, agreement between parents and teachers was modest (-.09 to .38). Cross-informant correlations were poor (-.09 to .27) for social skills, low (.15 to .36) for internalizing behaviors, and modest (.29 to .38) for externalizing behavior. Both parents and teachers rated boys as having more externalizing behavior problems than girls. Parents perceived their children to have more externalizing, and more overall, behavior problems than did teachers. In general, teacher reports, but not parent reports, were significantly associated with children's independently observed goal-directed activity, sustained attention, inappropriate behavior, peer affiliation, expressed negative affect, and proximity to a teacher in the classroom. Results argue for the clinical utility of the PKBS for teacher-report assessment of child behavior problems and social skills in the preschool years, and suggest the need for cross-contextual assessment. Also, it is clear that children's behavioral and social competence are crucial for optimal functioning in the preschool setting.  相似文献   

A Model for Inverting the Advanced Calculus Classroom     

Randy Combs  Teri Bingham  Taylor Roper 《PRIMUS》2018,28(8):717-725

In this paper I discuss my experience in using the inverted classroom structure to teach a proof-based, upper level Advanced Calculus course. The structure of the inverted classroom model allows students to begin learning the new mathematics prior to the class meeting. By front-loading learning of new concepts, students can use valuable class time for exploring and solving complex problems, with the instructor available for guidance and assistance. This paper compares student performance in the inverted classroom with student performance in the direct instruction classroom. I also share student perceptions of the inverted classroom experience.  相似文献   

Integrating Genomics Research throughout the Undergraduate Curriculum: A Collection of Inquiry-Based Genomics Lab Modules     

LM Banta  EJ Crespi  RH Nehm  JA Schwarz  S Singer  CA Manduca  EC Bush  E Collins  CM Constance  D Dean  D Esteban  S Fox  J McDaris  CA Paul  G Quinan  KM Raley-Susman  ML Smith  CS Wallace  GS Withers  L Caporale 《CBE life sciences education》2012,11(3):203-208

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Turnaround time and market capacity in contract cheating     

Melisa J. Wallace 《Educational studies》2014,40(2):233-236

Contract cheating is the process whereby students auction off the opportunity for others to complete assignments for them. It is an apparently widespread yet under-researched problem. One suggested strategy to prevent contract cheating is to shorten the turnaround time between the release of assignment details and the submission date, thus making it difficult for students to make arrangements with contractors. Here, we outline some characteristics of the current market for contract cheating and demonstrate that short turnaround times are unlikely to prevent contract cheating because requested turnaround times for university-level assignments completed via contract cheating are already short (average 5?days). In addition, for every contractor awarded a job, there are an average of 10 others offering to complete it within the specified time suggesting that there is abundant excess capacity in the market.  相似文献   

Scholarly Writing and the Pronoun     

Eunice Ewer Wallace 《College Teaching》2013,61(2)

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Library development in Swaziland     

Wallace Van Jackson 《International Information and Library Review》2013,45(4):367-377

Collaboration practices vary greatly per scientific area and discipline and influence the scientific performance and its scholarly communication. In this study, the collaborative pattern of the Information Retrieval (IR) research field is analyzed using co-authored articles retrieved from Social Science Citation Index for a period of 11 years from 1987 to 1997. The level of collaboration, journal collaborative distribution, disciplinary collaborative distribution and country collaboration are probed according to IR collaborative research. Findings are discussed from the above perspectives in detail. In particular, this study reveals a perceptible upward trend of collaborative IR research with the results of these research efforts being reported in all major core IR journals. The inter-disciplinary and intra-disciplinary scholarly communications in collaborative researches are very much in evidence and cover broad areas like psychology, and computer and medical sciences, respectively.  相似文献