EVALUATION OF MECHANICAL POWER OUTPUT MEASUREMENT IN A BENCH PRESS EXERCISE UNDER VARIABLE LOAD

The study is aimed to investigate evaluation of mechanical power output measurement during bench press exercise by methods which are used at training practice. As the criterion of power output measurement evaluation we selected a method which estimates the output by means of empirical 3D mechanical model (work in progress)

COMPARISON OF THE FORCE-TIME STRUCTURE OF THE VERTICAL JUMP BETWEEN MEN AND WOMEN

INTRODUCTION The vertical jump is a relatively simple movement situation which is very ofkn used for the study of the performance in take-off activities, quality of the muscles, coordination of the movement etc. (e.g. Komi & Bosco, 1978; Bobbert, F. M.,1988; Sanders, R. H., 1992,1993 and others). The vertical jump can be used as a very suitable model for the solution of many problems in sport pedagogy, effectiveness of the training process and studying of the movement quality of man. The object of our research is not only the final performance, (i.e. final characteristic of the jump - height of jump), but we are interested in the course of the movement, timing, stability - reproducibility of the movement and other aspects. This study was a part of a larger research project. The main goal of this study is to focus on the following questions: What was the inter-individual variability of the structure of the vertical jump? How was the stability (reproducibility) of the movement during the vertical jump? What were the differences in the structure of the vertical jump between the men and women? The classical counter-movement vertical jump was at the center of our interest. Students of physical education - men (n = 54, body height = 178.40 ± 6.12 cm, body weight = 70.29± 6.36 kg, age = 18 - 20 years) and women (n = 47, body height = 8.48± 6.20 cm, body weight 9.72 ± 6.44 kg, age = 18-20 years) were the subjects of the research. They performed two counter-movement vertical jumps. The vertical component Fz was registered by using the KISTLER platform. The reaction force Fz(t) was analyzed on an on-line system by using our own software which derived the velocity-time and distance-time functions from the Fz(t) curve and computed 23 biornechanical variables describing the structure of the vertical jump from the point of view of time, force, impulse, velocity, and the track of the center of gravity. Data were elaborated by statistical procedures based on STATGRAPHICS package (basic statistical characteristics, t-test, correlation analysis). Statistical characteristics of measured variables have provided the information about the inter-individual variability of the time, force, track, and velocity structure of the movement in the vertical jump for both men and women. This information was the basis for the next step of our research. Reproducibility of the structure of the vertical jump varies for different groups of variables (rtt = 0.50 - 0.98). The highest stability was found in the strength parameters (take-off force, braking and accelerating impulse, rtt = 0.91-0.98) and the lowest level of stability for the time structure of the movement (at = 0.45-0.66). Statistical analysis has confmed a significant difference in the structure of the vertical jump between the group of men and women

THE RELATIONSHIP BETWEEN ANTHROPOMETRIC BODY DIMENSIONS AND THE MODEL FOR WEIGHT LIFTING TECHNIQUE

INTRODUCTION The basic problem in learning weight lifting techniques is to define the optimum track of the bar-bell. The parameters of the bar-bellis track can be thought of as a basic criterion of the level of the weight lifting technique of an individual. The course of the bar-bell track is very individual and dependent on many different factors. One of the most important factors is the anthropometric body dimensions of the athlete. By using a special device which is called pantograph the general parameters of the bar-bell track can be defined. At present time a special simulator is being constructed which enables us to simulate the individual track of the bar-bell according to input data of the individual. The system is controlled by computer. The main goal of this research is to find the relationship between the anthropometric body dimensions of the individuals and the basic parameters of the barbell track. We expect that the parameters of the individual will be the input data for the simulation of the optimum bar-bell track for the individual. METHODS The research has been provided by a group of 29 top weightlifting athletes. Eight anthropometric data (length parameters) and 7 derived anthropometric values from previous data were the input data for the statistical analysis. By using the device of our own construction (pantograph) the track of the bar-bell for each individual has been measured. The model of the individual track of the bar-bell was expressed by 8 different measured characteristics. The best competition attempts were selected for the research. The basis for the statistical evaluation of measured data was the method of correlation and multiple regression analysis. By using these statistical methods, the relationship was examined between anthropometric dimensions and the characteristics of the bar-bell track (8 variables). We expect, that the regression equations will enable us to find the individual parameters of the bar-bell track which will be the input data to the simulation of the individual model of the bar-bell track. RESULTS - The range of multiple correlation coefficients was 0.45 to 0.94. Based on the multiple regression analysis the matrix of the anthropometric data was reduced to 5 selected significant variables (2 lengths and 3 derived parameters). Derived equations of multiple regression analysis enable us to compute the key parameters which define the individual bar-bell track. The results of this research will be used for the solution of the problem of learning the optimal technique of weightlifting by using the simulator

A COMPARISON BETWEEN THE KINEMATIC CHARACTERISTICS OF THE TRANSITION PHASE OF SKI-JUMPING ON JUMPING HILLS WITH DIFFERENT CRITICAL POINTS

The jumping hill construction is one of the major external factors which influence the ski-jump. The increase in the jumper's velocity reduces the time for the mainparts of the ski-jump. It is necessary to determine the influence of these changes on the transition phase in the ski-jump. The transition phase is the section from the edge of the hill to the beginning of the flight phase. This part is determined by many factors which occur during the takeoff. The magnitude of the aerodynamic forces increases with the high velocity. Therefore, for the quick implementation of the transition phase, the rotation of the ski-jumper has to increase. We suppose, that the inter individual differences between various performance levels of jumpers will increase. The purpose of this study was to find relationships between the kinematic characteristics of the transition phase on jumping hills with different constructional characteristics and to determine the degree to which jumpers at various skill levels are able to manipulate the technique. The study was carried out at the events held on the jumping hills with different critical points: - GP Frenstat pod Radhostem (K=90) – Intersport tournee Innsbruck 1995 (K=109) - World Championship in the ski flight Planica 1994 (K=185).The 2-D analyses were implemented using the System of Kinematic Analysis of Ski-jumping, which was presented on the XI1 International Symposium of Sport Biomechanics in Budapest. This system allows us to find the basic angle, length and velocity parameters for the transition phase of the ski jump. The sets of competitors in the 1st round (n=50-80) were divided -into three groups (n=12-15,B-best, M-middle, Glow) according to the length of jump. The statistical analyses were using the statistic package Statgraphics

THE INFLUENCE OF EXTRA LOAD ON TIME AND FORCE STRUCTURE OF VERTICAL JUMP

Extra load is very often used in the training for development of explosive strength. Some research works are focused on a problem of take-off activity in relationship to extra load (Nelson & Martin, 1985; Bosco et al., 1984 and others). The main aim of this study was to find how the extra load influences time and force curve of the vertical jump

COMPARISON OF ISOMETRIC AND DYNAMIC METHODS OF STRENGTH TRAINING PROGRAM

The purpose of this study was to determine the difference in the quality of muscle strength employing two methods of strength training (isometric, dynamic). Nineteen male university students volunteered to participate in the experiment, encompassing a five week strength training sessions. The dynamic method was applied to the elbow flexion and extension of the right side (load totalling 60 % of maximal performance) and the isometric method applied on the same muscle groups of the left side (maximal voluntary isometric contraction). Pre- and post-test measurements included maximal isometric strength, the angle a expressed the speed of increasing muscle strength and the number of repetitions performed for each exercise (at a of load 60 % max), as a measure of muscle endurance. No differences were found between the results of strength training when using both methods (isometric, dynamic). A five week training program improved the isometric force by about 8-14 % of pre-test values, and by about 34-54 % in repetition exercises with the load. No differences were exhibited in the rate of the speed of increasing muscle strength

A GENERAL VERSUS AN INDIVIDUAL MODEL OF THE SKI JUMPING TECHNIQUE

INTRODUCTION The stochastic models which are based on the results of biomechanical analyses of the ski jump (kinematic analysis, eg ARNOT, 1995; dynamic analysis of the take-off, e.g. VAVERKA, 1987) help us to solve the basic question of the relationship between the biomechanical variables and the criterion (validity). Statistical models form the output used to select the set of observed variables which represent the parameters for the effective ski jumping technique The results of many studies have shown that the validity of the biomechanical variables are very different in different phases of the ski jump. Contrary to what has been seen in practice it has been repeatedly found that the statistical dependence between take-off variables and the criterion are relatively low (R2 = 0.2-0.3) In comparison with the flight phases (R2= 0.6-0.9). The hypothesis of an individual model for the take-off is supported by the multifactor theory of the take-off (VAVERKA, 1987) in which the principle optimisation of the take-off factors and individualisation of the take-off have been defined. This paper represents an attempt to determine a practical model for ski-jumping technique. METHODOLOGY The system for the 20 kinematic analyses of the ski-jump (VAVERKA, 1994; take-off phase) and the Peak Performance Analyses System (flight phase) have been used in this study. The set of 11 variables for both the take-off and flight phase served as the input matrix for the statistical analyses (Intersporttournee event in Innsbruck 1993-1995, n=155). The set of 18 world class level athletes were selected for the study of intra-individual variability for the take-off phase. The average number of analysed take-offs by individuals was 7.6 jumps (range=5-13 takeoffs). Analyses of variance, multiple range of analyses of variance, regression, correlation and factor analyses computed by the STATGRAPHICS package were used. RESULTS The results of the statistical analyses on the inter-individual variability (5 matrices for the take-off phase and 6 matrices for the flight phase) demonstrated a low level of validity for the take-off parameters (R2 =0.15-0.20) and increased validity for the flight parameters (R2=0. 7-0.8) The statistical analyses of differences between individuals has shown that there are the significant differences in the aerodynamics and forward-backward position for the centre of gravity (relates to the factor of rotation). CONCLUSIONS The results of the statistical analyses have shown the predominant tendencies of individualisation of the take-off model. A very successful take-off for an individual could be realised by the use of many different patterns of movement. From the results of the flight phase we can accept a general pattern for the performance this ski-jumping phase REFERENCES Arndt, A. et al. (1995). Journal of Applied Biomechanics, 11, 224-237. Vaverka, F. (1987). Biomechanics of Ski-jumping (Czech language), Monograph, Univerzita Palackeho Olomouc, 235 pp. Vaverka, F. et al. (1994). In. Biomechanics in Sports XII, Proceedings, 285-287

THE ACCURACY OF THE SKI-JUMPER'S TAKE-OFF

Introduction The Ski-jumper's take-off is the key phase in Ski-jumping. The difficulty lies in the take-off is done a t great speed (20-30 m.6- ) and in a very short amount of time (0.2-0,4sec.). Based on multifactor theory .We have defined 5 factors which are necessary to solve in one movement act: vigour, accuracy, aerodynamics, rotation, arm activity (VAVERKA, 1987).The take-off is accurate in the moment when the acceleration of the center of gravity is finished and passes through the edge of the take-off area. Problem The main goals of t h i s paper are: - quantification of the take-off accuracy (kinematic and dynamic Aspect), - the relation of the accuracy t o the other factors of the take-off and to final performance in ski-jumping, - to create a model of take-off accuracy (kinematic and dynamic point of view) which would be useful in ski-jumper's training method We have been interested in solving these problems Prom the years 1984-1992. We used the following methods: - dynamometry of the ski-jumper's take-off in natural conditions of the jumping hill in Frenstat p.R. (the length of measured platform 6 m, artificially covered jumping-hill), about 800 take-offs were analysed, - kinematic analyses of the take-off (in years 1990-1991, about450 take-offs) analysed from different jumping hills - measurement of the speed during the run-on phase, - statistical and graphical methods. Results The long term observation of these problems revealed: - a large variability of this factor in relation to different levels of performers, different forms of hill surfaces, and patterns of take-off force-time curves, - close relation of accuracy to the length of jump and other factors of the take-off, especially vigour, - t h e possibility to create a statistical model enabling the quantification of the take-off accuracy by using results from dynamometric measurements and kinematic analyses

A KINEMATIC FOCUS ON THE RELATIONSHIP BETWEEN THE MAIN PHASES OF SKI JUMPING AND PERFORMANCE AT THE INNSBRUCK 1995 EVENT

Ski jumping is a unique sport discipline with a wide range of movements consisting of several follow-up phases. There is a selection of studies which have described each of the separate phases of the ski jump performance. However, the interaction between the movements of each of the main ski jump phases and their influence on the final performance have not been explored. The purpose of this project was to carry out a kinematic analysis of the entire ski jump performance and to determine the interrelationships between the various phases of the ski jump and between the final performance. The research was complete during the K120 world cup event Intersporttournee at Innsbruck on January 4th, 1995. The Innsbruck jumping hill provided an ideal environment for the location of each of the required cameras. In addition, the competition attracts a great a great number of top world athletes. The h t(n =50) and final (n=30) jump rounds were taped using seven cameras. Seven researchers from the three research groups who participated in this project (Czech Republic, Canada, and Slovenia) each operated a camera in order to record each of the five main phases: in-run, take-off, transition, flight 1 and flight 2. The kinematic data for each of the different phases were elaborated by using the 2D System of hematic Analysis of Ski-jumping (In-run, take-o& transition), the 3D Consport Motion Analysis System (transition), and the 2D Peak Performance System (flight 1, flight 2). The analysis also included measures of body dimensions (height, weight, and other anthropometric parameters), the length of jump, and the official in-run velocity. Analysis of variance, correlation, regression and factor analyses were used to statistically examine the data. The results of this research have added a new dimension to our understanding of the world's best ski jumpeis performances and the interrelationships between the movements in each of the critical phases

Evaluation of the Suitability of Intel Xeon Phi Clusters for the Simulation of Ultrasound Wave Propagation Using Pseudospectral Methods

The ability to perform large-scale ultrasound simulations using Fourier pseudospectral methods has generated significant interest in medical ultrasonics, including for treatment planning in therapeutic ultrasound and image reconstruction in photoacoustic tomography. However, the routine execution of such simulations is computationally very challenging. Nowadays, the trend in parallel computing is towards the use of accelerated clusters where computationally intensive parts are offloaded from processors to accelerators. During last five years, Intel has released two generations of Xeon Phi accelerators. The goal of this paper is to investigate the performance on both architectures with respect to current processors, and evaluate the suitability of accelerated clusters for the distributed simulation of ultrasound propagation using Fourier-based methods. The paper reveals that the former version of Xeon Phis, the Knight’s Corner architecture, suffers from several flaws that reduce the performance far below the Haswell processors. On the other hand, the second generation called Knight’s Landing shows very promising performance comparable with current processors