KINETIC AND KINEMATIC ANALYSIS OF RECURVE ARCHERY SHOOTING TECHNIQUE

The study investigated shooting techniques of the archers with kinetic and kinematic methods. Twenty-seven archers of different skill levels have been involved into the current study to investigate both muscular activation strategies of nine muscles and some kinematic data on drawing hand side. A statistical significant difference (p0.05) in the time-dependent exchange values of the angle of the joints, a difference was detected in the graphical sense. Elite archers use distal muscles less but proximal and axial muscles more, and mid-level and novice archers use distal muscles more to pull the bowstring. This was interpreted to be the most important factor affecting the horizontal oscillation (lateral diflection) of bowstring

Changes in Orbicularis Oris Superior and Masseter Muscle Activities After Upper Incisor Protrusion in Class II Division 2 Malocclusion: An Electromyographic Study

Objective:This prospective study aimed to evaluate the orbicularis oris superior and masseter muscle activity changes after upper incisor protrusion in CII/2 malocclusion.Methods:A total of 20 patients (mean age 10.29 ± 0.90 years) with CII/2 malocclusion were selected for the study group. A total of 15 patients (mean age 10.56 ± 1.06 years) with Angle Class I malocclusion were recruited as control. Upper incisors were protruded with utility arch in the study group. Muscle activities were evaluated with Biopac MP150 surface electromyography device before and after upper incisor proclination and at the 6-month retention. Orbicularis oris superior and left–right masseter muscles were recorded during rest electromyography and maximum contraction electromyography. Repeated measures and two-way repeated-measures analysis of variance with Bonferroni correction were used for statistical analysis.Results:A significant change occurred over time in orbicularis oris superior (P 0.05. In the CII/2 group, orbicularis oris superior maximum contraction electromyography value was increased after upper incisor protrusion and this increase remained stable. Left masseter and right masseter maximum contraction electromyography measurements were decreased after protrusion and then increased after retention significantly. Rest electromyography values for all muscles were not statistically significant. No significant differences with the control group were found.Conclusion:Upper incisor protrusion increased orbicularis oris superior activity and the increase remained stable after retention. Masseter activities decreased after protrusion and then increased to the initial values. These changes did not show significant differences with the control group

DEVELOPMENTAL DIFFERENCES OF KINEMATIC AND MUSCULAR ACTIVATION PATTERNS IN INSTEP SOCCER KICK

The aim of the study was to evaluate kinematic and muscular activation differences amongst different age groups of soccer players. Thirty male youth soccer players were divided into 3 groups according to their age (age 12-13; age 14-15; age 16-17). There were significant differences in ball velocities and isokinetic strength values amongst groups. Angular and linear velocities of hip, knee, ankle and toe were also significantly different (

Consistency In Acceleration Patterns Of Football Players With Different Skill Levels

The aims of the present study were to compare the consistency in the lower limb acceleration patterns during inside and instep kicks performed by players with different skill levels, and to investigate the correlation between subjective rating scores for skill level relative to their kicking performance and knee acceleration repeatability. Thirteen club-level male soccer players of ages between 15-16 years participated in this study. Skill levels of individual players were quantified previously by evaluating shooting performance as a numerical value ranging from 1 to 10. Further evaluations were held through tri-axial acceleration data recorded at proximal tibial tuberosity beneath each patella on the players' knees, in a procedure in which players were asked to complete four randomly ordered shooting trials of inside and instep kicks with 2-minute resting intervals. Hence, the mainstream data used in consistency calculations are in the form 4 by 1200 matrices (acceleration vs. time) per subject. In order to evaluate the consistency of acceleration data, the mean of the standard deviations (mSD) were calculated, and the associated Pearson-r correlation coefficients were incorporated to obtain mSD vs. skill correlations. As a result, repeatability was found to increase with skill level at z-axis acceleration for instep kicks only. However, it is possible to find the most appropriate orientation (for the two kicks) for meaningful correlations using vector rotations on the 3 orthogonal acceleration data, and this study shows that, after such suitable vector rotations, positive repeatability results could also be acquired for the inside kicks.Wo

Archery Skill Indexes: Estimation of Archers' Performance Level by Using Forearm Surface EMG Data

Surface EMG signals of m. flexor digitorum superficialis (MFDS) and m. extensor digitorum (MED) were recorded of 23 subjects during archery shooting. Two-second periods (clicker falls at 1th sec) of 12 shots' EMG data were recorded, rectified and averaged (moving average filter) for each subjects. 7 and 6 of the subjects were elite and beginner archers respectively, while rest is non-archers. Intra-archer mean value (IAMV) and standard deviations (IASD) of cross-correlations (CC) were calculated for each archer. Kruskal-Wallis Statistic was used for subject's IAMVs or IASDs vs. skill groups. Variation among group medians of IAMVs was statistically significant (p<0.05) for both MED and MFDS. But variation among group medians of IASDs was statistically significant (p<0.05) for only MED. The results show that when archery experience increases archers contract their MED or MFDS more similarly since CCs of EMG waveforms increase. IAMVs and IASDs of CCs may be a good candidate for a) assessing shooting techniques b) evaluation of archers' progress, and c) selection of talented archers

Determination Of Electromyography-Based Coordinated Fatigue Levels In Agonist And Antagonist Muscles Of The Thigh During Squat Press Exercise

Background. Simultaneous tiredness of two or more muscles around a joint can be defined as coordinated fatigue (co-fatigue) and might occur between agonist and antagonist muscles, and vary according to the level of sporting activity levels or gender. Objectives. The aim of this study was to determine the levels of coordinated fatigue in agonist and antagonist muscles during squat-press exercise. Methods. Twenty athletes and twenty sedentary subjects participated in the study. Surface electromyography signals of the rectus femoris, vastus lateralis obliquus, biceps femoris and semitendinosus muscles were recorded at the squat press position for 15 seconds during isometric contraction. Measurements were repeated five times and a 2-minute rest period was allowed between repetitions. After erroneous EMG elimination, movement artefacts were removed by using a 20 Hz high-pass Butterworth filter. Then, as a well-recognized fatigue index, the median frequency (MF) of each filtered middle part of the EMG signal (5 to 10 s. of contraction) was calculated, given that it is known that the MF decreases during isometric contractions. Finally, each MF-based co-fatigue index was calculated by dividing the mean RF and VLO median frequencies by the mean ST and BF median frequencies. The cumulative co-fatigue values of “male vs. female” and “sedentary vs. athlete” comparisons were performed by using a two-sided Student t-test with a Bonferroni correction. Results. There was a statistically significant (Bonferroni corrected p-value < 0.05) difference between the mean female (1.57 +/- 0.53) and the mean male (1.23 +/- 0.17) co-fatigue values, while there was no statistically significant difference between the mean co-fatigue values of sedentary (1.51 +/- 0.52) and athlete (1.29 +/- 0.27) subjects. Conclusion. The offered co-fatigue indices might be useful for other sports, physiotherapy and related areas if sufficient scientific proof is accumulated.WoSScopu

Effect of Touch Coordinate Display As a Form of Augmented, Concurrent Visual Feedback on The Accuracy of Single-Handed Typing Via Smartphone Virtual Keyboards

This study assessed the effect of an easily perceived real-time visual feedback method on touchscreen typing accuracy. Thirty subjects were asked to hold a smartphone with a capacitive touchscreen in one hand and enter a text using the thumb of the same hand via a custom designed virtual keyboard. There were two types of text entry sessions: with or without visual feedback. The visual feedback consisted of a full-screen crosshair, representing the accurate coordinate of touch in real time. In each session, touch-down time on the virtual keyboard and touch coordinates were recorded for every touch action. Two types of typing errors were defined: 1) centering error (CE), which was calculated as the mm distance between the coordinate of the touch and the center of the key, and 2) incorrect entry (IE), which was the number of missed keys. Student t-tests and Wilcoxon tests were used for mean and mean-rank comparisons of CE and IE, respectively. The results showed that visual feedback decreased CE (mean SD) significantly from 1.34 +/- 0.38 mm to 0.85 +/- 0.24 mm (P < 0.0005), and decreased IE (median and range, # of incorrect entries) significantly from 5.50 and 32.00 to 1.00 and 7.00 (P < 0.005). In conclusion, the accurate, easily perceived, and 2D real-time feedback decreases touch-typing error rates markedly and therefore can be of practical importance for increasing the productivity of smartphone users.WoSScopu

The Effect of Kick Type on the Relationship between Kicking Leg Muscle Activation and Ball Velocity

This study aimed to identify the effects of different kick types on the relationship between kicking leg muscle activation and ball velocity. The muscle activation of selected knee extensor and flexor muscles of 10 amateur soccer players were measured using electromyography during the performance of six maximal soccer kick types. The highest ball velocity was achieved by the instep kick (96.2 km/hr-1), followed by the lofted kick, the inside curve kick, the outside kick, the outside curve kick, and finally the inside kick (81.3 km/hr-1). There were significant positive correlations between muscle activation and ball velocity for the vastus lateralis and lofted (0.765), inside curve (0.792) and instep kicks (0.788), and for the gastrocnemious with the outside kick (0.796). Non-significant correlations between muscle activation and ball velocity exhibited a trend such that they were positive for the vastus medialis and vastus lateralis but negative for the biceps femoris and gastrocnemious for inside-foot-dominated kicks, while this trend was reversed for outside-foot-dominated kicks. According to results, the noted trends can be explained by the change in muscle activation patterns required to orientate the foot for each type of kick; this has implications for players’ training activities

Muscular coordination of movements associated with arrow release in archery

The aim of this study was to examine the muscular activation strategy of archers with different levels of expertise. Twenty-seven (27) male archers volunteered to participate in the current study. The activation of nine forearm and shoulder girdle muscles were analysed. Statistically significant differences were observed among the archery groups in the activation of muscles (flexor digitorum superficialis, extensor digitorum communis, deltoids middle, deltoids posterior, trapezius pars ascendens, trapezius pars transversa, and trapezius pars descendens) (p&lt;0.05). The results of this study, indicated that in order to pull the bowstring, the elite archers used distal (forearm) muscles less, but used proximal (shoulder) and axial (trapezius) muscles more, while the mid-level and novice archers used distal muscles more. This differential muscle use was interpreted as the most important factor affecting the horizontal oscillation of the bowstring. To minimise horizontal oscillation, it is suggested that archers carry the weight with their axial and proximal muscles. The findings of the present study could be used as a reference to pave the way for the development of effective archery training, which would include visual or audial feedback methods.Keywords: Archery; Electromyography (EMG); Muscular activation; Shooting