Long-axis rotation: The missing link in proximal-to-distal segmental sequencing     

R. N. Marshall  B. C. Elliott 《Journal of sports sciences》2013,31(4):247-254

Most assessments of segmental sequencing in throwing, striking or kicking have indicated a proximal-to-distal sequencing of end-point linear speeds, joint angular velocities, segment angular velocities and resultant joint moments. However, the role of long-axis rotations has not been adequately quantified and located in the proximal-to-distal sequence. The timing and importance of pronation-supination in the development of racquet head speed have been examined in the tennis serve and squash forehand drive and considered in relation to conventional concepts of proximal-to-distal sequencing. Both long-axis rotations reached their peak angular speeds late in both strokes, typically after shoulder flexion-extension, shoulder abduction-adduction and elbow extension. These results clarify and confirm the importance of upper limb long-axis rotations in the production of racquet head speed. It appears that traditional proximal-to-distal sequencing concepts are inadequate to describe accurately the complexity of the tennis serve or squash forehand drive. It is essential to consider upper arm and forearm longitudinal axis rotations in explaining the mechanics of these movements and in developing coaching emphases, strength training schedules and injury prevention programmes.  相似文献   

The penalty throw in water polo: A cinematographic analysis     

Bruce C. Elliott  Julie Armour 《Journal of sports sciences》2013,31(2):103-114

Three‐dimensional (3‐D) high‐speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3‐D space reconstruction from 2‐D images recorded via laterally placed phase‐locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M‐162°; F‐158°); the elbow angle showed significantly greater flexion for females (85°) than males (107°).

During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158° to 148° at release. The wrist movement for male subjects was different from the females in that it flexed from 162° to 147°, 0.10 s prior to release and then extended to 159° at palmar release before again flexing to 156° at release. The amount of elbow extension during the forward swing was 48° for both groups; however, the females actually released the ball with the forearm vertical (89°) compared to the male forearm angle of 78°. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F‐148°; M‐156° at wrist and F‐126°; M‐148° at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s ^‐1 and 14.7 m s^{‐ 1} for male and female subjects respectively.  相似文献   

Prevalence and psychological sequelae of self-reported childhood physical and sexual abuse in a general population sample of men and women     

Briere J  Elliott DM 《Child abuse & neglect》2003,27(10):1205-1222

OBJECTIVE: This study examined the prevalence and psychological sequelae of childhood sexual and physical abuse in adults from the general population. METHOD: A national sampling service generated a geographically stratified, random sample of 1,442 subjects from the United States. Subjects were mailed a questionnaire that included the Traumatic Events Survey (TES) [Traumatic Events Survey, Unpublished Psychological Test, Harbor-UCLA Medical Center, Los Angeles] and the Trauma Symptom Inventory (TSI) [Trauma Symptom Inventory Professional Manual, Psychological Assessment Resources, Odessa, FL]. Of all potential subjects, 935 (64.8%) returned substantially completed surveys. RESULTS: Sixty-six men and 152 women (14.2% and 32.3%, respectively) reported childhood experiences that satisfied criteria for sexual abuse, and 103 males and 92 females (22.2% and 19.5%, respectively) met criteria for physical abuse. Twenty-one percent of subjects with one type of abuse also had experienced the other type, and both types were associated with subsequent adult victimization. After controlling for demographics, adult history of interpersonal violence, and other child abuse, childhood sexual abuse was associated with all 10 scales of the TSI, and physical abuse was related to all TSI scales except those tapping sexual issues. Sexual abuse predicted more symptom variance than did physical abuse or adult interpersonal victimization. Various aspects of both physical and sexual abuse experiences were predictive of TSI scores. Abuser sex, however, both alone and in interaction with victim sex, was not associated with additional TSI symptomatology. CONCLUSIONS: Childhood sexual and physical abuse is relatively common in the general population, and is associated with a wide variety of psychological symptoms. These relationships remain even after controlling for relevant background variables.  相似文献   

Goal orientations in Russian university students: from mastery to performance?     

Richard Remedios  Zoya Kiseleva  Joe Elliott 《教育心理学》2008,28(6):677-691

Research in the UK has shown that students start their university career with the goal of mastering their subject, but this focus shifts as they progress through their degree program. Studies have suggested that unlike students in the UK, Russian students continue to take a strong mastery approach to their work. The main aim of this study was to assess whether the effects observed in UK studies could be found in a Russian context. In a cross‐sectional study, 618 students across four years of a degree program in a Russian university completed an achievement‐goal questionnaire. Results revealed patterns similar to the studies in the UK; Russian students’ levels of mastery were significantly lower after Year 1. The results are discussed in terms of potential changes in Russian culture. Methodological issues relating to the relative failure of some questionnaire items to validate fully within their hypothesised constructs are also discussed.  相似文献   

Differential Ability Scales – Second Edition (neuro)psychological predictors of math performance for typical children and Children with Math Disabilities     

James B. Hale  Catherine A. Fiorello  Ron Dumont  John O. Willis  Christopher Rackley  Colin Elliott 《Psychology in the schools》2008,45(9):838-858

Concerns about the ability‐achievement discrepancy method for specific learning disability (SLD) determination led to alternative research‐based methods, such as failure to respond to intervention. Neither of these regulatory methods address the statutory SLD definition, which explicitly includes a deficit in basic psychological processes. Examining neuropsychological processing differences among typical children and children with math SLD, commonality analyses revealed that Differential Ability Scales – Second Edition (DAS‐II) predictors accounted for more achievement variance in typical children (46% to 58%) than in children with math SLD (33% to 50%), with substantial loss of predictive validity when General Conceptual Ability was used instead of subcomponent scores. Results suggest that differences in typical predictor‐outcome relationships may provide a foundation for developing specific cognitive and academic interventions for children with math SLD. © 2008 Wiley Periodicals, Inc.  相似文献   

Evaluating the validity of the Automated Working Memory Assessment     

Tracy P. Alloway  Susan E. Gathercole  Hannah Kirkwood  Julian Elliott 《教育心理学》2008,28(7):725-734

The aim of the present study was to investigate the construct stability and diagnostic validity of a standardised computerised tool for assessing working memory: the Automated Working Memory Assessment (AWMA). The purpose of the AWMA is to provide educators with a quick and effective tool to screen for and support those with memory impairments. Findings indicate that working memory skills in children with memory impairments are relatively stable over the course of the school year. There was also a high degree of convergence in performance between the AWMA and the WISC‐IV Working Memory Index. The educational implications are discussed.  相似文献   

Performance tolerance and boat set-up in elite sprint kayaking     

Ong K  Elliott B  Ackland T  Lyttle A 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(1):77-94

The aim of this study was to examine the inter-relationship between athlete morphology, equipment set-up and performance in elite sprint kayaking. Correlations applied to data from the 2000 Olympics were used to select the most important links between morphology and boat set-up--paddle grip width and foot-bar distance. Associations between body size and the above selected equipment set-ups were calculated using a Pearson correlation matrix, to facilitate the logical selection of independent variables as input for regression analyses. Significant (p < 0.01) regression equations were developed for the prediction of foot-bar distance (r2 = 0.589: standard error of estimate (SEE) = 4.48) and paddle grip width (r2 = 0.541: SEE = 3.08). Three national-standard sprint kayakers used their preferred set-up together with modifications of their predicted set-up, derived from Olympic data, to test performance tolerance in sprint kayaking. Mean coefficients of multiple determination over three trials for the three paddlers of 0.91, 0.91 and 0.92 for left paddle force, right paddle force, and paddle angle at water entry, respectively, were recorded when using their preferred set-up. These data showed that the paddlers produce consistent patterns of motion. The intervention of altering the boat set-up resulted in varying changes to boat speed. The mean preferred speed for the three paddlers of 4.47 m/s was reduced by 0.07 and 0.10 m/s when the above boat set-up was modified to a predicted and 'predicted plus one standard deviation'respectively. These changes in boat speed were the result of alterations in the mechanics of paddling technique.  相似文献