Kicking Accuracy Research Articles

The Effect of Internal Imagery Training on Increasing the Accuracy of Free Kicks for Young Indonesian Football Athletes Aged 13 Years

The Effect of Internal Imagery Training on Increasing the Accuracy of Free Kicks for Young Indonesian Football Athletes Aged 13 Years

Impact of competitive learning method on the accuracy of direct free kicks in football among male university students

The objective of the present research was to study the impact of the competitive learning method on the accuracy of direct free kicks in football among male university students. The research community was composed of the 90 third-year male students of the College of Physical Education and Sports Sciences of the University of Al-Qadisiyah, in the academic year 2020-2021. A total of 24 of these 90 students were randomly selected for the research sample, and they were equally divided into two experimental groups of 12 students. The experimental group 1 used only the competitive learning method, while the experimental group 2 used the competitive learning method and the Football Jumping Wall Device. The statistical analyses were carried out with the Statistical Package for Social Sciences (SPSS). The competitive learning method significantly improved the accuracy of direct free kicks in football among male university students. The combination of competitive learning method with the use of the Football Jumping Wall Device was more effective than the use of the competitive learning method alone. Therefore, the authors recommend the combined use of the competitive learning method and the Football Jumping Wall Device to improve the accuracy of direct free kicks in football among male university students.

TREINAMENTO DE FORÇA NA ESTABILIDADE NOS CHUTES DOS JOGADORES DE FUTEBOL

ABSTRACT Introduction: The physical condition of soccer players in sports competitions has improved over the years. The optimal performance of their professional skills in competitive conditions has become essential for victory in soccer matches. Objective: This paper explores the effects of different methods employing strength training on soccer kicking techniques aiming at the set that best enables the accuracy of hits through its stability. Methods: 36 soccer players were randomly divided into the experimental and control groups, with no statistical difference in fitness and the comprehensive ability characteristics of the players. Both subjects were trained for 12 weeks; only the experimental group received the special strength training intervention for stability. The passing score of the curve ball in 20-meter dribbling was measured before and after training. The data were statistically treated. Results: The kicking accuracy of soccer players in the experimental group differed from before the test (P<0.01). There was also a significant difference in kicking accuracy in the control group (P<0.05). The 20-meter arc dribbling scores in the experimental group were statistically significant compared to those before the test (P<0.05). There was no significant difference between the control group and the test scores on curve ball passing scores in 20-meter dribbling (P>0.05). Conclusion: Functional strength methods to achieve the goal of improving kicking accuracy in athletes have been developed. Coaches should pay attention to physical training, an attitude that encourages players to achieve sufficient physical strength for soccer games with their kicking skills. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

The Effect of the Quadriceps Muscle Fatigue After an ISOTONIC Contraction on Some Kinematic Variables and the Accuracy of Soccer Players’ Performance of the Corner Kick

Fatigue in muscles is a reason for the low skill performance of soccer players so this study sought to find out the effect of the quadriceps muscle fatigue resulting from an isotonic contraction on some kinematic variables and the accuracy of soccer players’ execution of the corner kick. A test for the accuracy of the corner kick and the leg press exercise was used on a sample of 8 international soccer players, and their means were as follows: age: 26.8 ±2.3 years, height: 174 ±12 cm, mass: 71 ±6 kg, training age: 14.6 ±1.8 years. The performance of the corner kick test was videotaped by three cameras and Kinovea program for kinematic analysis was used. The results showed a negative effect of the quadriceps muscle fatigue after isotonic contractions on kinematic variables and on the accuracy of corner kicks. The study results point to the necessity of enhancing the ability of soccer players in terms of endurance of muscle strength in the quadriceps muscle to the highest possible extent due to the importance of that element in their skillful performance, including the accuracy of the implementation of corner kicks.

The effectiveness of using power fitness training loads to increase adaptive reserves of female athletes in hand-to-hand combat

Background and Study Purpose. One of the main aspects of improving the special training of athletes in hand-to-hand combat is increasing functional reserves in conditions of power loads. Study Purpose - to study the peculiarities of adaptive body changes and the level of special training in female athletes of hand-to-hand combat using power fitness programs with different structure, parameters, and means.
 Material and Methods. We examined 36 female athletes (18-20 years old) who had been engaged in hand-to-hand combat for the last 4 years. We divided these women into two groups,18 people in each group. Groups used completely different power fitness training programs. We used methods of testing special training (the number of accurate kicks on the mannequin for 30 s) and laboratory monitoring of blood biochemical parameters (cortisol and LDH) before and after training load during 3 months. Group A used the standard power fitness training program for women of this age (exercises on simulators). Group B used well-known exercises with their own body weight with a complete change of kinematic and dynamic characteristics of the technique during 3 months of training.
 Results. The obtained results showed that indicators of special training positively changed by 10.4% (p <0.05) in group B athletes. At the same time, the studied indicator increased by 2.2% compared to initial level in group A athletes. At the end of the study, we observed an increase in cortisol level in the blood serum of group B athletes in response to physical stimuli. This was almost 10 times lower than the results recorded in group A. The results of monitoring LDH activity in the blood serum showed that its level increased by 19.5% (p <0.05) during the entire study period only in group B athletes. The controlled indicator remained almost unchanged in group A. The dynamics of the studied steroid hormone and enzyme in the blood serum in group B indicated an increase in the level of organism resistance to training loads under specified conditions of muscular activity and their pronounced adaptive changes.
 Conclusions. Determining the most effective power fitness training program for special training of female athletes in hand-to-hand combat, will help to increase their adaptive body reserves and their level of fitness. For this using different in structure and parameters training load.

Relationship between Agility, Speed, Leg Muscle Strength, Dynamic Balance with Mawashi Geri Kick Accuracy in Karate

This study aims to examine the relationship between agility, speed, leg muscle strength, dynamic balance and the accuracy of the mawashi geri kick in karate. This research uses correlational research method. The object of this research is female athlete Forki Wonogiri. The data collection technique used purposive sampling with a population of 149 karate athletes and a sample of 60 female karate athletes aged 12-18 years. The research instrument used a dogging run test (agility), a 30 meter run test (speed), a leg dynamometer test (leg muscle strength), and a modified bass test (dynamic balance). The results showed that there was a significant relationship of 0.747 and the interpretation of the correlation coefficient value that the accuracy of the mawashi geri kick had a strong positive relationship with a contribution of 60%. The conclusion of this study there is a negative relationship between agility and speed, a positive relationship between leg muscle strength and dynamic balance with the accuracy of the mawashi geri kick, which is significant so that the hypothesis is accepted. In order for the Training Center activities, especially the mawashi geri kick to be successful, a senpai or trainer should provide exercises through movements that can improve agility, speed, leg muscle strength, and dynamic balance by doing these exercises on a scheduled or routine basis. so that it can increase stamina and karate sports performance for the better.

Relationship between Agility, Speed, Leg Muscle Strength, Dynamic Balance with Mawashi Geri Kick Accuracy in Karate

Relationship between Agility, Speed, Leg Muscle Strength, Dynamic Balance with Mawashi Geri Kick Accuracy in Karate

A Preliminary Study on Factors Influences the Design of Soccer Shoes Among Malaysian Soccer Players

Soccer is a contact sport, so a soccer shoe's design is important because it affects the kick's accuracy, speed, and ability to avoid foot injuries. A research study with an appropriate experimental design and precise execution is necessary to produce high-quality results. A pilot study can be conducted as an external pilot study apart from the main study or as an internal pilot study integrated into the main study's research plan. This paper will review the research conducted from a pilot project to identify the design factors such as anatomy, anthropometry, biomechanics and physical characteristics for a soccer shoe popular amongst Malaysian soccer players. The objectives of this research are to determine the accuracy of the questionnaire items. The initial sample consisted of 50 Men soccer players from Peninsular Malaysian states are randomly selected from various levels of the game and have at least one year of playing experience. This study used the quantitative method, whereby questionnaires were applied to obtain information from respondents and findings were analyzed using SPSS software version 23.0 to calculate the Cronbach's Alpha reliability index. The validation of the instrument involves a total of two expert panels. A total of 84-item survey is divided into 4 sections, covering the demographic information of the respondents, their professional backgrounds, their opinions on soccer shoes, and their perceptions on shoe design elements. This study has shown that 81 items were appropriate to be utilized to measure the selection of soccer shoes design. Overall, these results indicate that the analysis has statistically proved that the items in this instrument has a high degree of validity and reliability and can be used for study’s actual sample. The high value of the alpha coefficients suggest that the instruments is very reliable and capable of determining the accuracy of the questionnaire items.

Analytical study of some biokinematic variables and their relationship to the strength and accuracy of performance of the front circular kick for Taekwondo players

The aim of the search is to: Codification of a skill test according to the electronic drip system for the front circular kick for Taekwondo players, as well as to identify the values of some biokinematic variables for the front circular kick for Taekwondo players and to identify the values of the two variables (strength and accuracy) of the front circular kick for Taekwondo players according to the electronic drip system, in addition to identifying the relationship between the values of Some biokinematic variables and the productive force for the performance of the front circular kick for taekwondo players according to the electronic drip system, as well as revealing the relationship between the values of some biokinematic variables and the accuracy of the front circular kick for taekwondo players according to the electronic drip system. The researchers hypothesized that there is a significant relationship between the values of some biokinematic variables and the producing force of the front circular kick of Taekwondo players according to the electronic drip system, and the existence of a significant relationship between the values of some biokinematic variables and the accuracy of the front circular kick of Taekwondo players according to the electronic drip system. The researchers used the descriptive approach using the two survey methods and the correlational relationships for its relevance and the nature of the study. The research community consisted of taekwondo players, the advanced category, which numbered (75) players representing the players of the teams (Baghdad, Nineveh, and Erbil). The research sample consisted of a sample of the two exploratory experiments, the number of its members (9) players were chosen from the research community, five of them from the Nineveh Governorate team, the tests for the front circular kick were applied, and four from the Erbil Governorate team to apply the biokinematic analysis tests. And the sample of the application of the tests consisting of (50) players representing the teams (Baghdad, Nineveh, and Erbil), and the stability sample consisting of (10) players, in addition to the analysis sample, they are (6) players who were chosen in a deliberate way who represent (3) from the Nineveh Governorate team and ( 3) From the Erbil governorate team. The researchers used measurement, testing, and technical scientific observation as means of data collection. The scientific observation was carried out using three video cameras at a speed of (100) images/sec. The researchers also used the electronic drip system device imported by them to record successful kicks and then obtain points. The best kick during which the player obtains the best strength and performance accuracy to be analyzed using kinetic analysis programs. The data were statistically processed using the SPSS program to obtain the data (arithmetic mean, standard deviation, simple correlation coefficient, t-test for independent samples) and equations that are related to biokinematic variables. The researchers concluded that the standardized tests of the front circular kick for strength, speed, and accuracy were It has a positive role in revealing the most important Biokinematic variables that achieve a touch recording according to the electronic drip system. The biokinematic variables of the front circular kick had an effective effect in applying the appropriate and effective force in scoring points according to the electronic scoring system during training or a fight. And in light of these conclusions, the researchers recommended the necessity of providing and using the electronic drip device during training and friendly fights between players for the category of applicants, due to the importance of this system in determining the player’s achievement. The necessity of using the electronic scoring device on other samples of different groups (juniors, youth) during the training.

Criteria for assessing the adaptive changes in mixed martial arts (MMA) athletes of strike fighting style in different training load regimes.

BackgroundTo study the peculiarities of changes in functional indicators and body composition parameters of mixed martial arts (MMA) athletes of strike fighting style and a number of biochemical blood indicators during two months of using different intensity training load regimes, and to determine the most informative criteria for assessing adaptive body changes in these training conditions.MethodsWe examined 40 MMA athletes (men) aged 20–22, who used mainly strike fighting style in their competitive activity, and divided them into 2 research groups (A and B), 20 athletes in each group. Group A athletes used medium intensity (Ra = 0.64), and group B—high intensity (Ra = 0.72) training load regime. To assess the adaptive body changes we applied methods of control testing of maximum muscle strength growth (1 RM), special training (the number of accurate kicks on the mannequin for 30 s), and bioimpedansometry. By monitoring biochemical parameters (testosterone, cortisol, creatinine, phosphorus, calcium, cholesterol, LDH) in the blood serum of athletes, we determined the peculiarities of adaptive-compensatory body reactions in response to training loads.ResultsThe obtained results of special training increased during the study period by an average of 10.5% in group B athletes, but group A participants’ results had no significant changes compared to basal data. The largest increase in the development of maximum muscle strength growth by an average of 44.4% was recorded after 2 months of research in group B. Group B athletes also had positive changes in body fat and fat-free mass indicators during the study which were two times higher than the results of group A. The laboratory studies and correlation analysis showed informative biochemical markers (cortisol, testosterone and creatinine) for assessing the condition of athletes in both groups before using high and medium training load regimes. The biochemical markers for assessing the adaptive-compensatory reactions of athletes in response to high-intensity physical stimuli at the beginning of the study were indicators of LDH and cholesterol, and in conditions of medium intensity it was LDH, testosterone and cortisol. After 2 months of study the set of biochemical markers assessing the adaptation processes before the load completely changed only in group B athletes and consisted of LDH, phosphorus, cholesterol, and calcium. At the same time, the set of biochemical criteria for assessing adaptive-compensatory reactions after training in group B athletes was completely changed compared with the data recorded at the beginning of the study.ConclusionDefining the optimal set of criteria for assessing the adaptive-compensatory changes in MMA athletes of strike fighting style will allow in the shortest possible time to correct the parameters of the training load regime for accelerating the body functionality in the process of special power training.

Analytical study of some biomechanical variables and their relationship to the strength and accuracy of performance of the front circular kick for Taekwondo players

The aim of the search is to: Codification of a skill test according to the electronic drip system for the front circular kick for Taekwondo players, as well as to identify the values of some biomechanical variables for the front circular kick for Taekwondo players and to identify the values of the two variables (strength and accuracy) of the front circular kick for Taekwondo players according to the electronic drip system, in addition to identifying the relationship between the values of Some biomechanical variables and the productive force for the performance of the front circular kick for taekwondo players according to the electronic drip system, as well as revealing the relationship between the values of some biomechanical variables and the accuracy of the front circular kick for taekwondo players according to the electronic drip system. The researchers hypothesized that there is a significant relationship between the values of some biomechanical variables and the producing force of the front circular kick of Taekwondo players according to the electronic drip system, and the existence of a significant relationship between the values of some biomechanical variables and the accuracy of the front circular kick of Taekwondo players according to the electronic drip system. The researchers used the descriptive approach using the two survey methods and the correlational relationships for its relevance and the nature of the study. The research community consisted of taekwondo players, the advanced category, which numbered (75) players representing the players of the teams (Baghdad, Nineveh, and Erbil). The research sample consisted of a sample of the two exploratory experiments, the number of its members (9) players were chosen from the research community, five of them from the Nineveh Governorate team, the tests for the front circular kick were applied, and four from the Erbil Governorate team to apply the biokinematic analysis tests. And the sample of the application of the tests consisting of (50) players representing the teams (Baghdad, Nineveh, and Erbil), and the stability sample consisting of (10) players, in addition to the analysis sample, they are (6) players who were chosen in a deliberate way who represent (3) from the Nineveh Governorate team and (3) From the Erbil governorate team. The researchers used measurement, testing, and technical scientific observation as means of data collection. The scientific observation was carried out using three video cameras at a speed of (100) images/sec. The researchers also used the electronic drip

Acute Effects of Partial Range of Motion Resistance Training and Increases in Blood Lactate Impact Accuracy of Penalty Kicks in Soccer Players.

The purpose of this investigation was to assess the acute effects of partial range of motion (pROM) exercises, on the accuracy of soccer penalty kicks on goal. This method limits the joint from moving through the complete length of a motion, creates an occlusion effect, and thus causes the type 1 muscle fibers to work anaerobically. Thirty-six soccer players, with 5-8 years of soccer playing experience, were pretested for accuracy then retested (rtt = 0.92) and divided into random groups from the Associação Banco do Brasil Futebol Clube—Group A, Paraná Futebol Clube—Group P, and Coritiba Futebol Clube—Group C. Groups were composed of 12 people performing full range of motion (fROM) exercises or pROM exercises. Both groups performed 5 sets of back squats at 50% of body weight in sets of 40 seconds with metronome tempo of 56 bpm for an average of 10-12 repetitions per 40-second set. Blood samples were collected post-warm-up, after the 3rd set, and following the 5th set for both groups, within 3–5 minutes of cessation of exercise. Athletes performing fROM exercises showed increased blood lactate from 2.69 ± 0.2 to 4.0 ± 1.2 mmol/L (p < 0.05), and in pROM, blood lactate increased from 2.48 ± 0.42 to 10.29 ± 1.3 mmol/L (p < 0.001). In fROM, accuracy decreased from 42.96 ± 13.39% to 41.37 ± 17.25% (p > 0.1), a slight decrease, while in the pROM groups, accuracy decreased from 45.42 ± 14.93% to 24.53 ± 10.2% (p < 0.001). The calculations demonstrating average percentages of accuracy are presented in the tables. These findings support that pROM exercises significantly increase blood lactate resulting in a reduction in soccer kick accuracy. This decrease in accuracy directly correlates to the accumulation of lactic acid and hydrogen ions (H+) and demonstrates that pROM strength training should not be utilized prior to a sport-specific session in order to avoid interference with the development of special skills.

Statistical modelling of goalkicking performance in the Australian Football League

ObjectivesAustralian football goal kicking is vital to team success, but its study is limited. Develop and apply Bayesian models incorporating temporal, spatial and situational variables to predict shot outcomes. The models aim to (i) rank players on their goal kicking and (ii) create clusters of statistically similar players and rank these clusters to provide generalised recommendations about player types. DesignRetrospective longitudinal study with goal kicking data from three seasons, 2018–2020, 576 official Australian Football League matches, containing 26,818 attempts at goal from 778 players. MethodsThe Bayesian ordinal regression model enables descriptive analysis of goal kicking performance. The models include spatial variables of distance and kick angle, situational variables of shot type and player or cluster with interaction terms. Alternative models included situational variables of weather and player characteristics, spatial variables of stadium location and temporal variables of time and quarter. Approximate leave-one-out cross validation was used to test the model. ResultsOverall goal rate of 47% (12,600), behind rate of 35% (9373) with misses the remaining 18% (4845). Accuracy of both player and cluster model achieved 0.51 against an uninformed (predict goal) model result of 0.47. The models allow for analysis of goal kicking accuracy by distance and angle and analysis of player and player-type performance. ConclusionsWhile credible intervals for all players for set shots and general play were relatively large, some 95% credible intervals excluded zero. Therefore, it may be concluded that some players' goal kicking skill can be quantified and differentiated from other players.

A comparative study of instep kicking swings, ball impacts, and ball speeds in male and female football players

This research aims to compare swings, ball impacts, and ball velocities of instep kick between male and female players. The research used comparative design method, in which two groups of males and females were compared. This research used eight Indonesian football players as sample: four males and four females. The instrument used for data collection in this research is football long pass test. Video documentation was taken with high-speed camera unit with 1000 fps ability. The data collected were then analyzed through Kinovea, in which swing angles, foot angular velocities, ball impact times, ball velocities, and resulting ball distances were calculated. Non-parametric Mann-Whitney test were used to compare each instep kick of male and female players. Results show that no difference on instep long pass swing and ball impact between male and female players was observed. On average, male players performed instep kicking with kicking foot knee flexion angle of 104.750, hip angle of 77.250, kicking foot knee extension angle of 1580, kicking foot steepness angle of 58.250, average power of 209.38 J/s (watt), and average kicking foot angular velocity of 0.11 rad/s, which resulted in average ball impact of 10.27 Ns that caused average post-impact ball velocity of 22.83 m/s and average ball distance of 26.63 meters. Meanwhile, female players performed instep kicking with kicking foot knee flexion angle of 930, hip angle of 74.250, kicking foot knee extension angle of 1480, kicking foot steepness angle of 56.250, average power of 237.28 J/s (watt), and average kicking foot angular velocity of 0.11 rad/s which resulted in average ball impact of 10.32 Ns that caused average post-impact ball velocity of 22.94 m/s and average ball distance of 26.87 meters. The results show that the average ball distance of male players was closer to 25-meter target than those of female players. In order to achieve 25-meter kicking accuracy, female players contributed greater power and steeper kicking foot angle than their male counterparts. In conclusion, to master instep kicking technique, female players need to pay attention to their power and body position during kicking.

EFFECTS OF THE FIFA 11+ AND HARMOKNEE WARM-UP PROGRAMS ON PHYSICAL PERFORMANCE MEASURES ININDIAN ELITE FOOTBALL PLAYERS (AN EXPERIMENTAL STUDY)

This study was carried to determine the benefits of fifa 11+ and harmoknee warm-up protocol in indian male football players and conclude the superiority between the two established protocols in accordance with their effects on sprinting, vertical jump, kicking accuracy, and agility. 45 healthy male footballers (mean age 21.44±5.3yrs, height1.76±0.2m&amp;weight 73.19±11.5kgs) participated in the study. The participants were equally divided into group a= fifa 11+, group b = harmoknee, and the control group. The experimental groups (gp a &amp;gp b) underwent training for 6 weeks, and trained for 20 minutes per session on all days except sunday (36 sessions), whereas the control group performed their regular football training. The performance tests carried out were the 20m speed test, vertical jump test, illinois agility test, and wall volley test. The results were analyzed by spss version 17. Within-group pre and post comparisons were done using paired t-test, an inter-group comparison was done using one-way anova followed by multiple comparisons bonferroni. The level of significance for all tests was set at 5% (p=0.05). In the present study, the vertical jump was improved significantly only in gp a (6.75% increase, p=0.001) as compared to gp b (p=0.082) &amp; the control group (p=0.291). While agility improved in both gp.a (7.23% increase, p=0.00) &amp; gp.b (5.43% increase, p=0.001), no significant improvements were observed in the kicking accuracy &amp; sprinting ability in all the 3 groups within group comparison. However, on inter-group comparison, significant differences were observed between group a&amp; b (p=0.009) with gp b demonstrating more kicking accuracy as compared to gp a. 6-weeks training of 11+ warm-up program enhance vertical jump and agility but it does not improve player’s kicking accuracy and sprinting ability and the harmony program improves agility but has no positive effect on sprinting and kicking accuracy in young professional male footballers. 11+ injury prevention programs can be implemented to enhance agility and vertical jump in young male football players.

Age- and size-corrected kicking speed and accuracy in elite junior soccer players

ABSTRACT Kicking powerfully and accurately is essential in soccer, and players who kick proficiently with both feet are highly sought after. Assessing performance in youth players is often confounded by more physically developed players outperforming their smaller peers. To alleviate such bias, we present a testing protocol and normative data developed with an elite Brazilian soccer academy that controls for players’ age and size to assess kick performance with both feet. We measured kick speed and kick accuracy of 178 players and recorded their age (10–20 years), height, and mass. Combining age, height, and mass into an age and size index (ASI), we developed equations describing the relationship between ASI and performance. To determine the underlying predictors of performance, we also measured sprint ability and soccer-specific motor control of each foot with ball dribbling tasks. Kicking speed with the dominant foot was predicted by ASI, sprint speed, and motor control of the nondominant foot, while kicking speed with the nondominant foot was predicted by ASI and motor control of the nondominant foot. Kick accuracy with each foot was predicted by ASI and motor control of the corresponding foot. To improve kicking performance, we suggest training programs focus on motor control.

Biomechanical analysis of long pass in U-19 women football players

Kicking movement is process of moving position on leg. Biomechanical analysis explains kick performance which influenced by kinematics and kinetics factors. The research purpose analyzed biomechanical long pass movement. This research is both qualitative and quantitative. The research sample are 11 Indonesian woman football players who were taken by saturated sampling. Data in the form of long pass kick video with airborne ball test. Data analyzing used Kinovea software to determine the flexion angle of backswing kick leg, hip angle, and distance to target, then looking for the force, power, and energy in kick motion. The motion analysis shown that sample 3 produces closest distance to target as far as 0.65 m which done with flexion angle of backswing knee is 740 and hip angle of 640. The force exerted by sample 3 is 10.09 N, resulting in a ball speed of 22.42 m/s and a kinetic energy of 113.12 Joule, potential energy of 14.64 Joule and mechanical energy of 127.76 Joule. It can be concluded that accuracy of long pass kick are influenced by flexion angle of backswing kick knee, hip angle, power and force as well as producing energy in the form of kinetic, potential, and mechanical energy.

The effect of approach velocity on pelvis and kick leg angular momentum conversion strategies during football instep kicking

ABSTRACT During football instep kicking, whole-body deceleration during the final stride has been associated with greater kick leg angular momentum and enhanced foot and ball velocities, but the influence of approach velocity on these mechanisms is unknown. This study assessed how approach velocity affects momentum conversion strategies of experienced players performing fast and accurate kicks. Eleven semi-professional footballers performed instep kicks from self-selected (3.34 ± 0.43 m/s), fast (3.71 ± 0.33 m/s) and slow (2.77 ± 0.32 m/s) approaches. Kicking motions and ground reaction forces under the support leg were captured using 3D motion analysis (1000 Hz). The players responded to perturbations in approach velocity by using the support leg to regulate whole-body deceleration and create ideal conditions for co-ordinated pelvic and kick leg momentums during the downswing. Further, the pelvis was key for generating transverse momentum at the kick leg, but the participants displayed distinctly different pelvis transverse rotation strategies. Identification of these inter-individual strategies may provide a basis for technical and strength training practices to be tailored for individual players. Future research might investigate if training practices that expose footballers to varying approach velocities of between 2.5 and 4.0 m/s promotes development of movement strategies that are robust to perturbations in approach conditions.

6D Localization and Kicking for Humanoid Robotic Soccer

Robotic soccer simulation is a challenging area, where the development of new techniques is paramount to remain competitive. Robotic skill evolution has accelerated with recent developments in deep learning algorithms, leading to improvements in behavior number and complexity. Shooting a ball towards a defined target is one of the most basic yet indispensable skills in soccer. However, fast and accurate kicks pose several challenges. In order to reach that target, the skill is highly dependent on the ability of the agent to self-locate and self-orient, in order to better position itself before the kick. To tackle these issues, a 6D localization technique was devised. To optimize the kick behavior, two scenarios were proposed. In the first, the robot walks to the ball, stops, and then kicks. In the second, it kicks the ball while moving. We used state-of-the-art algorithms — Proximal Policy Optimization and Soft Actor Critic — to solve these complex problems and show their applicability in the context of RoboCup. Obtained results have shown very significant improvements over previously used behaviors by FC Portugal 3D team. The new kick in motion executes 5 times faster than the previous kick, and the new 6D pose estimator has an average error of just 6.3mm, a reduction of more than 97%.

Effects of a lower limb muscular fatigue on posture-movement interaction during a lower limb pointing task.

The aim of the present study was to investigate the effects of muscular fatigue on the interaction between posture and movement during a lower limb pointing task. Participants (n = 16), aged 18-30years, kicked a ball toward a target in four conditions of fatigue: No muscular fatigue (NF), fatigue in the kicking (FM) or postural limb (FP) alone, and fatigue in both limbs (FMP). The mean amplitude and speed of the centre of foot pressure (CoP) and centre of mass (CoM) displacements were estimated through a force platform and an optoelectronic system, respectively. In addition, surface electromyography (EMG) of the biceps femoris, rectus femoris, medial gastrocnemius, and peroneus longus was recorded to investigate the anticipatory postural adjustments (APAs). Muscular fatigue yielded a decreased kicking accuracy (p < 0.001) and an increased time to perform the movement (p < 0.001), mainly during the backswing motion. In addition, significant increases in the mean amplitude and speed of the CoP and CoM displacement were found in the anteroposterior (AP) and mediolateral (ML) axes (ps < 0.001), especially when both limbs were fatigued. The EMG analysis confirmed that fatigue modified the way APAs were generated. During fatigue, postural muscle activity increased, but was delayed with respect to movement onset (ps < 0.001). This pattern of response was more consistent when both limbs were fatigued (p < 0.001). The present results suggested an additive effect of fatigue and a functional adaptation and subsequent decrease in the overall variability of APAs, indicating that postural and motor processes are interdependent.