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The main goal of the present study was to examine muscle strength and power of dominant and non-dominant leg, knee extensors and flexors, and their correlations with jumping performances in soccer players. A secondary aim was to evaluate muscle sense. Methods: 31 male professional strikers (age 20.9 ± 2.3 years, body mass 75.1 ± 6.6 kg, body height 179.5 ± 4.7 cm) participated in the study. The power output of lower extremities and the height of rise of the body mass centre during vertical jumps were measured using a force plate. The maximum muscle torque of the flexors and extensors of the knee were measured under isometric conditions using a special isometric torquemeter. Force sense was measured in isometric conditions in two tests: (a) fifty percent of the maximal voluntary contraction was set as a value of target force and the participants were instructed to reproduce the target force, (b) the participants attempted to develop a torque reproducing a sine course within the range of 10 to 50% of MVC performed. Results: A direct relationship was observed between the peak muscle torque in knee extensors developed during isokinetic contraction at all velocities and power and height of three types of vertical jumps ( p < 0.05). No correlation was observed between jumping performance and muscle torque under isometric condition. No differences were found in strength and jumping abilities as well as in force sense between dominant and non-dominant legs. Conclusions: This study offered a comprehensive and complete evaluation of leg muscle strength, sense and power, with the use of using force plate and isokinetic dynamometry.
EN
The aim of this study was to identify the determinants of peak power achieved during vertical jumps in order to clarify relationship between the height of jump and the ability to exert maximum power. Methods: One hundred young (16.8±1.8 years) sportsmen participated in the study (body height 1.861 ± 0.109 m, body weight 80.3 ± 9.2 kg). Each participant performed three jump tests: countermovement jump (CMJ), akimbo countermovement jump (ACMJ), and spike jump (SPJ). A force plate was used to measure ground reaction force and to determine peak power output. The following explanatory variables were included in the model: jump height, body mass, and the lowering of the centre of mass before launch (countermovement depth). A model was created using multiple regression analysis and allometric scaling. Results: The model was used to calculate the expected power value for each participant, which correlated strongly with real values. The value of the coefficient of determination R2 equalled 0.89, 0.90 and 0.98, respectively, for the CMJ, ACMJ, and SPJ jumps. The countermovement depth proved to be a variable strongly affecting the maximum power of jump. If the countermovement depth remains constant, the relative peak power is a simple function of jump height. Conclusions: The results suggest that the jump height of an individual is an exact indicator of their ability to produce maximum power. The presented model has a potential to be utilized under field condition for estimating the maximum power output of vertical jumps.
EN
Purpose: The aim of the study was to develop a method to measure and analyse kinematics of movement of the pelvic girdle in butterfly swimming in order to support training of technical skills. Methods: A device for recording triaxial accelerations and triaxial rotational angular velocities was mounted on the dorsal part of the pelvic girdle of athlete. The measurements were performed in ten elite butterfly swimmers (age: 23.1 ± 3.7 years, body height: 187.6 ± 4.3 cm, body mass 83.4 ± 6.33 kg). The task of the athlete was to swim one length of short course pool at maximal intensity. Individual mean graphical and numerical profiles of the kinematics of the movement of the pelvic girdle was computed, within the average cycle based on five consecutive cycles. Results: Statistical analysis of numerical individual parameters of profiles of the athletes studied revealed statistically significant differences between the swimmers. Statistically significant correlations were also found between personal best times in 50 m swimming (r = –0.76, p < 0.05) and 100 m swimming (r = –0.76, p < 0.05) and duration of the part of the cycle connected with the decline in velocity from maximum translational motion velocity obtained during propulsion with the upper and lower limbs to minimum value of the velocity obtained before the beginning of propulsion only with the lower limbs. Conclusion: The proposed measurement method, presentation and analysis of the profile of the pelvic girdle motion in butterfly swimming represents a good tool for fast and effective qualitative and quantitative biomechanical evaluation of movement technique components.
EN
The main aim of the study was to design a new system to measure punching and kicking forces as well as reaction times in combat sport athletes. In addition, the study examined whether there were any intergender differences in the force of punches thrown by boxers and kicking forces delivered by taekwondo athletes. Boxers (male, n = 13; female, n = 7) were examined for the force of single straight punches and taekwondo athletes (male, n = 14; female, n = 14) for force of single Apdolio and Dwit Chagi kicks. The punching bag was equipped with acceleration transducers and gyroscopes embedded in a cylinder covered with a layer to absorb shock as well as a set of colour signal diodes. Value of the punching bag’s acceleration was used for calculating: strike force; the punching location on the bag; and time of a strike. The relative error of force calculation was 3%; the relative error in acceleration measurement was less than 1%. The force of a straight rear-hand punch was greater than the force of a lead-hand punch among male and female boxers. The force of Apdolio kick delivered with a rear leg was greater compared to a lead leg among female and male taekwondo athletes. Significant gender differences were noticed in the force in both types of kicks. In boxers, intergender differences were reported only for the force of a punch thrown with the rear hand. Based on these findings, it was concluded that the modified punching bag is a good diagnostic tool for combat sports.
EN
The aim of the study was to follow the changes of the maximal muscle torque of male volleyball players during training performed in the preparatory and starting period. Muscle torque measurements in static conditions were performed in preparatory (I, III) and starting (II, IV) periods for two years. The sum of muscle torque of the trunk and sum of muscle torque of lower extremities were decreases between I and II period, and increases between III and IV period. The sum of muscle torque of upper extremities were significantly increases between III and IV period. The significant differences between II and IV period were observed for upper extremities.
EN
The work presents analyze of vertical acceleration curve of the body mass center (VACM characteristic) obtained by eleven athletes during on treadmill running with gradual rise velocity. The measurements are made by uniaxial accelerometer placed in loins part of trunk near the center of body mass. The chosen value of characteristics was calculated for every single run with applied velocity of treadmill The velocity of treadmill of every run was significantly correlated to mean values of VACM characteristics calculated for all subjects. For every athletes analyzed mean values of characteristics calculated separately for left and right steps were significantly different.
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