A kinematic comparison between long-line and cross-court top spin forehand in competitive table tennis players

ABSTRACT

The aim of the present study was to compare the biomechanical characteristics of the table tennis top spin shot when played cross-court (CC) or long-line (LL) in competitive table tennis players. Seven national level players respectively completed 10 long-line and 10 cross-court top spin shots responding to a standard ball machine. A stereophotogrammetric system was used to track body segments while executing the motion. Significantly more flexed right knee and elbow angles were measured at the moment of maximum velocity of the racket (MMV) in LL. In addition, significantly greater angles between the feet and the table and between the shoulders and the table at the MMV, indicated more pronounced rotation angles of the lower upper and upper-body in LL compared to CC with respect to the table. A higher inclination of the racket at the MMV was found in LL. The elbow flexion and the racket inclination may be associated to the direction of the shot. The present findings show that kinematic differences exist between the LL and the CC topspin forehand in competitive table tennis players. Coaches should be aware of these differences to adopt the optimal teaching strategies and to reproduce proper joint angles during training.     

Three-dimensional kinematic analysis and power output of elite flat-water kayakers

The purpose was to examine power output and three-dimensional (3D) kinematic variables in the upper limbs, lower limbs and trunk in elite flat-water kayakers during kayak ergometer paddling. An additional purpose was to analyse possible changes in kinematics with increased intensity and differences between body sides. Six male and four female international level flat-water kayakers participated. Kinematic and kinetic data were collected during three tasks; low (Int_L), high (Int_H) and maximal (Int_M) intensities. No differences were observed in any joint angles between body sides, except for shoulder abduction. Significantly greater range of motion (RoM) values were observed for Int_H compared to Int_L and for Int_M compared to Int_L in trunk and pelvis rotation, and in hip, knee and ankle flexion. The mean maximal power output was 610 ± 65 and 359 ± 33 W for the male and female athletes, respectively. The stroke frequencies were significantly different between all intensities (Int_L 59.3 ± 6.3; Int_H 108.0 ± 6.8; Int_M 141.7 ± 18.4 strokes/min). The results showed that after a certain intensity level, the power output must be increased by other factors than increasing the joint angular RoM. This information may assist coaches and athletes to understand the relationship between the movement of the kayaker and the paddling power output.     

Methods and Techniques Used in Significant Restoration Projects in Qatar

The large number of conservation and restoration works recently completed in Qatar show that there exists a need to enhance appreciation of the local architectural and building traditions, as a way of bringing to light the historical memory of these local places, using local techniques and materials to conserve existing buildings and to typologically integrate them. This paper offers an update on the status of some recent conservation projects in Qatar, analysing and comparing a number of completed restorations of historic buildings on the basis of the categories into which they can be organised; the extent to which they had deteriorated before restoration; the methods that were adopted; the construction materials and techniques used; the philosophical approach taken to restoration; and the various proposals for reusing the restored buildings. Comparison and analysis of the data make it possible to classify these methods and techniques in ways that could be applied to other conservation projects in future. The aim is to define a philosophy and methodologies that are consistent, and will be able to give expression to the specific local culture in matters of conservation, while respecting shared international rules.     

A Model for Vibration Monitoring of Immovable Art in Churches: Reflections on Monitoring as a Tool for Preventive Conservation

ABSTRACT

During construction of a 6 km long railway tunnel close to historic churches in Stockholm, a preventive monitoring model was applied for ensembles of large-scale immovable ecclesiastical artworks. Construction work such as blasting and pile-driving took place during five years under or very close to these immovable works of art. In Sweden, risk assessment related to construction work is focused on risks associated with the building; meanwhile, there is no common approach for protecting the immovable historic works of art and architectural surfaces. This paper discusses how a preventive model for vibration monitoring on immovable artworks was developed and used as well as how the preventive purpose was perceived by different stakeholders during and after the tunnelling work. Experience from this project concludes that monitoring that includes uniform visual inspection becomes crucial for being able to protect the artworks. The concept of vibrations standards relying on fixed numbers of critical vibrations levels for mitigating the effects of vibration on immovable art can be questioned based on experiences from this project.     

Situating Expertise in Practice: Domain-Based Data Management Training for Liaison Librarians

The research data management team at the University of California, Berkeley implemented a domain-based Librarian Training Program in order to upskill liaison librarians in research data management principles and create a community of practice among librarians providing research data support. The training program partnered with representatives from each subject division of the Library to integrate content from relevant disciplines. The training model emphasized scaffolding and concrete deliverables, teaching specific tools and concepts, and creating learning objects useful for instruction and outreach. Employing a situated, learning-based, pedagogical model, the program was more successful than previous attempts at library-wide research data management training at Berkeley. This analysis details the program management, curricular design, instruction, and outcomes that made the Library Training Program successful.     

À la mémoire de Tamàs Varga

Sans résumé