COMPARISON OF UPPER LIMB REACTION SPEED BETWEEN YOUNG TABLE TENNIS AND BADMINTON ATHLETES USING THE LYMMIC ELECTRONIC SYSTEM

The aim of the present study was to compare the upper limb reaction time between young athletes (boys) of table tennis and badminton. Two groups of 14 table tennis and badminton athletes (a total of 28 athletes) with a mean age of 14±1.65 and mean involvement in these sports of 5±1.32 were the sample of the study. The visual stimulus tests used to record reaction times were as follows: a) left hand simple reaction time test, b) right hand simple reaction time test, c) left hand choice reaction time test, d) right hand choice reaction time test. The tools used for the measurements were a special light sensor and other technological means. ANOVA and Duncan’s multiple range test (p<0.05) were applied for statistical data processing. The analysis of the results showed no statistically significant differences in any of the 4 tests of the athletes. The findings and the way of measuring reaction speed could be used by the athletes’ coaches to enrich and improve the training process.  Article visualizations

Political travel across the ‘Iron Curtain’ and Communist youth identities in West Germany and Greece in the 1970s and 1980s

This article explores tours through the Iron Curtain arranged by West German and Greek pro-Soviet Communist youth groups, in an attempt to shed light on the transformation of European youth cultures beyond the ‘Americanisation’ story. It argues that the concept of the ‘black box’, employed by Rob Kroes to describe the influence of American cultural patterns on Western European youth, also applies to the reception of Eastern Bloc policies and norms by the Communists under study. Such selective reception was part of these groups’ efforts to devise a modernity alternative to the ‘capitalist’ one, an alternative modernity which tours across the Iron Curtain would help establish. Nevertheless, the organisers did not wish such travel to help eliminate American/Western influences on youth lifestyles entirely: the article analyses the excursions’ aims with regard to two core components of youth lifestyles in Western Europe since the 1960s, which have been affected by intra-Western flows, the spirit of ‘doing one’s own thing’ and transformations of sexual practices. The article also addresses the experience of the travellers in question, showing that they felt an unresolved tension: the tours neither served as a means of Sovietisation nor as an impulse to develop an openly anti-Soviet stance.PostprintPeer reviewe

Analysis and design of a gear tooth crack-growth sensor for real-time measurement

90 σ.Στην παρούσα διπλωματική εργασία, αναπτύσσεται μια μέθοδος που βασίζεται στην πτώση του ηλεκτρικού δυναμικού, η οποία επιτρέπει τον προσδιορισμό σε πραγματικό χρόνο του μήκους της ρωγμής στον πόδα οδόντος μετωπικού οδοντωτού τροχού ευθείας, μετωπικής οδοντώσεως. Για να σχεδιασθεί ο αισθητήρας είναι απαραίτητο να εκτιμηθεί η επίπεδη παραμορφωσιακή κατάσταση στην επικίνδυνη διατομή του οδόντος. Εκτελείται στατική ανάλυση πεπερασμένων στοιχείων στον οδόντα εφαρμόζοντας ένα ομοιόμορφα κατανεμημένο, μοναδιαίο φορτίο κάθετα στο ανώτερο σημείο μονής επαφής του. Η ρωγμή ξεκινάει στο σημείο της μέγιστης κύριας τάσης σ1 και η τροχιά της προσδιορίζεται και σχεδιάζεται με βάση διατμητικά κριτήρια (τύπου Tresca και von Mises). Εισάγεται συνεχές ρεύμα από ένα ζεύγος ηλεκτροδίων και από ένα δεύτερο ζεύγος μετράται η διαφορά δυναμικού. Τα αποτελέσματα συσχετίζονται με τo πραγματικό (%) μήκος της ρωγμής. Η βέλτιστη θέση τοποθέτησης των ηλεκτροδίων εντοπίζεται εκτελώντας ηλεκτροστατική ανάλυση πεπερασμένων στοιχείων.In this thesis an electrical potential difference method for the real-time assessment of the length of a gear root crack is presented. In order to design and study a crack sensor for gear teeth it is necessary to assess the stress conditions prevailing in the vicinity of the tooth root . In this report , a Finite Element Analysis (FEA) of single spur gear teeth loaded at their HPSTC was performed and the location of the critical cross-section as well as the crack path were determined assuming a maximum shear stress criterion. Two measuring electrodes were placed in selected positions over the gauge area of a spur gear tooth and their readings were associated with the actual position of the crack tip using FEA. The optimum position of the two measuring electrodes was found performing rigorous Electrostatic Field Analysis Simulations.Ανδρέας Ε. Νικολακάκη

Análisis de la efectividad de los elementos técnico-tácticos durante la fase de servicio-recepción en jóvenes atletas de tenis de mesa

The aim of the current study was to record and compare the technical and tactical elements of the strokes during serve, receive and winning shots between winning and defeated female table tennis athletes, belonging to the cadet leagues and to study their relation with the outcome of the match. The sample for this study was 36 official table tennis matches (2487 rallies) of cadets (14 ± 1.48 years). The technical and tactical analyses was concerned with the type and direction of the serve and receiving the ball, the success rates of the player serving and receiving, as well as the process of winning a point after an offensive shot. In order to record and analyze the matches, the method of video analysis was used and for the statistical treatment of the data the non-parametric X2 test was implemented. The results revealed that the forehand grip was mainly used for the execution of a serve and the serve of the young female winners was statistically superior to the losers, regarding the score and the rates of successfully receiving the ball. Statistically significant differences were also observed in the first return of the ball after the execution of the serve, where the winners preferred mostly the forehand-push, backhand-topspin and forehand-topspin, making even more winning shots compared to the losers. The findings of the current study could be used by coaches in Cadet Leagues to improve training methods and help them to provide feedback to the athletes during the matches.El objetivo de este estudio fue grabar y comparar los elementos técnicos y tácticos de los golpes en el servicio, la recepción y los golpes ganadores (winner shots) entre atletas de tenis de mesa mujeres ganadoras y derrotadas que pertenecen a ligas cadetes, y estudiar su relación con el resultado del partido. La muestra para este estudio fue de 36 partidos oficiales de tenis de mesa (2487 rallies) de cadetes (14 ± 1.48 años). Los análisis técnicos y tácticos estaban relacionados con el tipo y dirección del servicio y la recepción, las tasas de éxito de la jugadora al servir y recibir, así como el proceso de ganar un punto luego de un golpe ofensivo. Con el fin de grabar y analizar los partidos, se usó el método de análisis de video y para el tratamiento estadístico de los datos se usó la prueba no paramétrica X2. Los resultados revelaron que el agarre forehand era usado principalmente para la ejecución de un servicio, y el servicio de las mujeres ganadoras jóvenes fue estadísticamente superior al de las perdedoras en cuanto al puntaje y las tasas de recepción exitosa. También se observaron diferencias significativas estadísticamente en la primera devolución de la pelota luego de la ejecución del servicio, cuando las ganadoras prefirieron principalmente el forehand-push, el backhand-topspin y el forehand-topspin lograron más golpes ganadores comparadas con las perdedoras. Los hallazgos del presente estudio pueden ser útiles para los entrenadores en las ligas cadetes para que mejoren sus métodos de entrenamiento y puedan brindar una mejor retroalimentación a las atletas durante los partidos

Análisis de la efectividad de los elementos técnico-tácticos durante la fase de servicio-recepción en jóvenes atletas de tenis de mesa

The aim of the current study was to record and compare the technical and tactical elements of the strokes during serve, receive and winning shots between winning and defeated female table tennis athletes, belonging to the cadet leagues and to study their relation with the outcome of the match. The sample for this study was 36 official table tennis matches (2487 rallies) of cadets (14 ± 1.48 years). The technical and tactical analyses was concerned with the type and direction of the serve and receiving the ball, the success rates of the player serving and receiving, as well as the process of winning a point after an offensive shot. In order to record and analyze the matches, the method of video analysis was used and for the statistical treatment of the data the non-parametric X2 test was implemented. The results revealed that the forehand grip was mainly used for the execution of a serve and the serve of the young female winners was statistically superior to the losers, regarding the score and the rates of successfully receiving the ball. Statistically significant differences were also observed in the first return of the ball after the execution of the serve, where the winners preferred mostly the forehand-push, backhand-topspin and forehand-topspin, making even more winning shots compared to the losers. The findings of the current study could be used by coaches in Cadet Leagues to improve training methods and help them to provide feedback to the athletes during the matches.El objetivo de este estudio fue grabar y comparar los elementos técnicos y tácticos de los golpes en el servicio, la recepción y los golpes ganadores (winner shots) entre atletas de tenis de mesa mujeres ganadoras y derrotadas que pertenecen a ligas cadetes, y estudiar su relación con el resultado del partido. La muestra para este estudio fue de 36 partidos oficiales de tenis de mesa (2487 rallies) de cadetes (14 ± 1.48 años). Los análisis técnicos y tácticos estaban relacionados con el tipo y dirección del servicio y la recepción, las tasas de éxito de la jugadora al servir y recibir, así como el proceso de ganar un punto luego de un golpe ofensivo. Con el fin de grabar y analizar los partidos, se usó el método de análisis de video y para el tratamiento estadístico de los datos se usó la prueba no paramétrica X2. Los resultados revelaron que el agarre forehand era usado principalmente para la ejecución de un servicio, y el servicio de las mujeres ganadoras jóvenes fue estadísticamente superior al de las perdedoras en cuanto al puntaje y las tasas de recepción exitosa. También se observaron diferencias significativas estadísticamente en la primera devolución de la pelota luego de la ejecución del servicio, cuando las ganadoras prefirieron principalmente el forehand-push, el backhand-topspin y el forehand-topspin lograron más golpes ganadores comparadas con las perdedoras. Los hallazgos del presente estudio pueden ser útiles para los entrenadores en las ligas cadetes para que mejoren sus métodos de entrenamiento y puedan brindar una mejor retroalimentación a las atletas durante los partidos

Comparison of the service and reception between winning and defeated high-level table tennis athletes

The aim of the present study was to compare service and reception in winning and defeated Table Tennis athletes. The sample of the survey consisted of 64 games (34 men and 30 women) of the A1 Table Tennis Greek national league, where a total of 5,065 points were analysed between 33 male athletes and 18 female athletes, who are among the best 32 of the official Hellenic Table Tennis Federation ranking. The variables analysed were: service grip, service execution length, reception technique, reception movement, the point conquest of the serving athlete and the point advantage in the first three hits. The non-parametric-square test(x2) showed that statistically significant differences were found between winning and defeated men, in the length of the service, with winners having a more effective service and more offensive reception. As for the female athletes, statistically significant differences were found in the grip and length of the service between winning and defeated women, while it was found that the winners have better service, perform defensive shots in the reception, and have an advantage in the first three hits. The above findings will help high-level athletes, coaches, physical trainers and performance analysts in understanding the importance of serving and receiving in high-level Table Tennis

COVID-19 and its consequences on mental health (Review)

As one year is approaching since the beginning of the Coronavirus disease 2019 (COVID-19) pandemic, it is important to acknowledge the detrimental effect that it is having on mental health at the individual, societal and public health levels. The current review presents the direct and indirect psychological impact of COVID-19 on the general public, as well as on vulnerable groups, including the elderly, the young, healthcare professionals, people with pre-existing mental health issues, those infected by COVID-19, homeless people and refugees. Important findings are discussed in the present review, including the social stigma in older people associated with portraying COVID-19 as the disease of the elderly, and the limited psychological impact of COVID-19 in the severely mentally ill, alongside the response of the mental healthcare systems globally to this unparalleled public health crisis. The important lessons to be learnt so far can help formulate individual mental health recommendations, as well as improved intervention and prevention public health strategies