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  • Author: Andrzej Mastalerz x
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Biomechanical Analysis of Successful and Unsuccessful Snatch Lifts in Elite Female Weightlifters

Abstract

The aim of this study was to identify biomechanical factors affecting successful and unsuccessful snatch attempts in elite female weightlifters during the 2013 World Weightlifting Championships. Fourteen female competitors took part in this study. Their successful and unsuccessful snatch lifts with the same load were recorded with 2 camcorders (50 Hz), and selected points were digitized manually on to the body and the barbell using the Ariel Performance Analysis System. The kinetic and kinematic barbell movement as well as the athlete’s body movement variables during the liftoff phase were examined. The results of this study show statistical differences (p ≤ 0.05) between successful and unsuccessful attempts in relation to the angle values in the knee and hip joints in preparation for the aerial phase position. Similarly, the center of gravity velocity was significantly higher in successful attempts during the catch phase. Thus, coaches should pay particular attention to the accuracy of the execution in preparation for the aerial phase position and to the velocity of the center of gravity of the competitors during the catch phase.

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Effectiveness of the Power Dry-Land Training Programmes in Youth Swimmers

Effectiveness of the Power Dry-Land Training Programmes in Youth Swimmers

The aim of the study was to evaluate the effects of the dry-land power training on swimming force, swimming performance and strength in youth swimmers. Twenty six male swimmers, free from injuries and training regularly at least 6 times a week, were enrolled in the study and randomly assigned to one of two groups: experimental (n=14, mean age 14.0 ± 0.5 yrs, mean height 1.67±0.08 m and mean body mass 55.71 ±9.55 kg) and control (n=12, mean age 14.1 ± 0.5 yrs, mean height 1.61±0.11 m and mean body mass 49.07 ±8.25 kg). The experimental group took part in a combined swimming and dry-land power training. The control group took part in swimming training only. The training programmes in water included a dominant aerobic work in front crawl. In this research the experimental group tended to present slightly greater improvements in sprint performance. However, the stroke frequency insignificantly decreased (-4.30%, p>0.05) in the experimental group and increased (6.28%, p>0.05) in the control group. The distance per stroke insignificantly increased in the experimental group (5.98%, p>0.05) and insignificantly decreased in the control group (-5.36%, p>0.05). A significant improvement of tethered swimming force for the experimental group (9.64%, p<0.02) was found, whereas the increase was not statistically significant in the control group (2.86%, p>0.05). The main data cannot clearly state that power training allowed an enhancement in swimming performance, although a tendency to improve swimming performance in tethered swimming was noticed.

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The Relationship Between Biomechanical Indicators of the Snatch Technique and Female Weightlifters' Levels

Abstract

Introduction. The snatch technique is a discipline in Olympic weightlifting. The lifter has to raise the barbell from the platform directly above their head in one movement. While reviewing the literature on biomechanical analysis of the techniques of weightlifting, one can find positions on the analysis of parameters, such as barbell track, horizontal displacement, and angular positions of the joints in the individual phases of the lifter's movement. Many texts concern female and male lifters taking part in World or European Championships. The parameters of the best competitors are outlined - mostly those who finish in the top five places in competition. Mostly these are parameters regarding male lifters, and less frequently those of female lifters. In the literature review, an overlooked aspect is that of the definition of the diversity of indicators as regards the snatch technique practiced by female lifters depending on score. Material and methods. In the research, registered snatch attempts during the World Championship were used. Videos were used by judges to establish a maximum weight limit for female lifters. The attempts were registered by two cameras and were later digitally processed by the APAS 2000 system. Barbell parameters, maximum speed, average of the bar, and the parameters of the lifter-bar collocation (horizontal displacement of barbell weights and height elevation) were assessed. Results. The analysed attempts show the margin of error for measurement of the average speed of the barbell as 0.03 m/s. The difference in maximum speed of analysed attempts is 15%. The height of clearance of the first-placed female lifter's barbell was 12.7 cm, 30 cm for the last-placed. Conclusions. The sporting level of weightlifting by female lifters influences the analysed biomechanical indicators of the snatch. Those indicators, which are similar in the case of both the World Championship winner and the female lifter who came last, may be described as the average speeds of the barbell. The high sporting level of female lifters performing heavy lifting is characterized by the clearance of the barbell.

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Effect of two Backpack Designs on Cop Displacement and Plantar Force Distribution in Children during Upright Stance

Abstract

Introduction. Many studies have compared different backpack designs and their influence on the carrier; however, no data referring to school students aged 7-8 years are currently available. Therefore, the aim of the research was to assess the influence of backpack design on centre of pressure (COP) displacement and plantar force distribution in children during an upright stance. Material and methods. Nineteen school students (9 males and 10 females) volunteered for the study. Two Polish backpacks intended for school use were evaluated: backpack A, which had two main compartments, and backpack B, which had one main compartment. The backpack load was composed of books, binders, and regular school equipment. During the measurements, the subjects were asked to look ahead with the head straight and arms at the sides in a comfortable position and to stand barefoot on the F-Scan® sensors (Tekscan, F-Scan®) attached to the force platform (Kistler), carrying a load corresponding to 10% of their body mass. Results. The study found insignificant differences between the two backpack designs. Moreover, COP parameters increased significantly during an upright stance while carrying backpack B in comparison to the empty backpack condition. Additionally, we observed significantly higher values of plantar force distribution in the heel region for the condition without load and insignificantly higher ones for carrying backpack A. Conclusions. The results of the current study suggest that the differences between the two backpack designs are too marginal to be detected through COP displacement. Disturbances in plantar force distribution suggest a lack of posture control and a lower stability of the standing position with a backpack, but these disturbances were significant only when the backpack with one main compartment was used.

Open access
The Effects of Different Types of Verbal Feedback on Learning a Complex Movement Task

The Effects of Different Types of Verbal Feedback on Learning a Complex Movement Task

Introduction. The aim of the study was to assess the efficiency of learning complex movement tasks with the use of different types of verbal feedback. Material and methods. Thirteen students randomly assigned to two groups (E&P=7; P=6) took part in the study. Results. In learning a movement task verbal information on errors and correctness (E&P) was more efficient than verbal information on correctness (P). Conclusion. At early stages too much information hinders the process of learning.

Open access
Biomechanical Criterions to Estimate Round-Off Tucked Performance Among Acrobats Aged 10-11

Biomechanical Criterions to Estimate Round-Off Tucked Performance Among Acrobats Aged 10-11

Introduction. The aim of the study was to carry out a biomechanical analysis of performing key elements of sports technique of the round-off tucked back somersault by acrobats aged 10-11. Material and methods. Thirty male acrobats participated in the study. They were randomly assigned to two groups: experimental (n=15) and control (n=15). Training experiment (specially designed training program applied in the experimental group), experts' evaluation and film analysis were the methods used to evaluate effects of experiment. Results. The results of the experimental group were statistically significantly better than in the control group (p<0.05). Conclusion. Training program based on teaching and improving key elements of technique may be recommended as one of the effective ways of teaching and improving the technique of selected acrobatic exercises of a coordinationally complex movement structure.

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The Influence of Different Training Conditions on the Kinematics of Long Jump-Specific Exercise in Young Female Jumpers

Abstract

Introduction. This study examined the changes in the kinematic parameters of long jump-specific technical exercise performed in different training conditions.

Material and methods. The study involved a group of young female athletes who volunteered to participate in the research. The key variables for long jump performance were measured using the Xsens MVN system. A three-way ANOVA (general linear model with repeated measures; factors: surface × hurdle × number of jumps) was used to determine if significant differences existed between the testing conditions.

Results. The main finding of this study was that the tartan surface resulted in significantly (p < 0.05) greater velocities of the centre of mass of the body (CM) or parts of the athlete’s body than the grass surface. The second important finding was that the hurdles condition provided significantly (p < 0.05) greater velocity of the CM when landing and shorter contact time compared to the condition without hurdles.

Conclusions. The findings of the study indicate that technical exercise should be performed on harder surfaces such as a tartan track rather than softer ones (e.g. grass) due to more beneficial movement characteristics and greater potential for the automaticity of movement during specific training tasks.

Open access
The Effects Of Swimming And Dry-Land Resistance Training Programme On Non-Swimmers

Abstract

Introduction. The aim of the study was to estimate the influence of combined swimming and dry-land resistance training on swimming force, swimming performance and strength in non-swimmers.

Material and methods. Thirty male non-swimmers took part in the research. They were randomly assigned to one of the two groups: experimental (n=17) and control (n=13). The experimental group took part in combined swimming and dry-land resistance training. The control group took part in swimming training only. The swimming and dry-land resistance training programme lasted twelve weeks (48 training sessions of swimming and 36 sessions of dry-land resistance training). Average training volume and intensity were the same for all swimmers throughout the study protocol. The training programme included dominant aerobic work in front crawl.

Results. Dry-land resistance training applied in the experimental group significantly improved the upper body strength. In spite of the theory that dry-land strength training is probably not specific enough to improve the sprint swim performance, the experimental group tended to demonstrate greater improvement in sprint performance. The imitation of the underwater phase of shoulder work during front crawl provided by the ergometer can be a useful training method in non-swimmers.

Open access
Benefits of Bandwidth Feedback in Learning a Complex Gymnastic Skill

The aim of this study was to examine the effects of two different frequencies of feedback during the process of learning a complex gymnastic skill, the round-off salto backward tucked. Thirty male acrobats participated in the study. They were randomly assigned to two groups: B - bandwidth feedback (n=15) or C - 100% feedback (n=15). Group B was provided with error information regarding the key elements of movement techniques only (bandwidth feedback). Our research demonstrates the advantage of augmented feedback information related to errors in the key elements. Information about errors in the key elements during learning a complex gymnastic skill prevents the gymnast from becoming overwhelmed, which promotes better motor control. These results provide support for the generalisation of bandwidth feedback principles to a complex task. Our research shows that the guidance hypothesis can also be tested in practical settings for a complex movement task.

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Direction and Velocity of the Ball in Volleyball Spike Depending on Location on Court

Abstract

Introduction. The aim of this study was to determine the correlations between the direction and velocity of the ball in volleyball spike. We adopted the hypothesis that the direction of an attack is dependent upon the arrangement of the pectoral girdles in the phase of flight.

Material and methods. The research was carried out for four different types of attacks: from the left side of the court down the line (A) and in the cross-court direction (B) and from the right side in the same directions (C and D). Sixteen young volleyball players from a Sports Championship School run by the Polish Volleyball Federation were examined.

Results. The analysis of the results showed different ball velocities in different attacks. The velocity was the lowest in attack B and the highest in attack D.

Conclusions. The direction of attack was produced by hitting the ball in a non-central manner and by aligning the glenohumeral joints diagonally to the net.

Open access