Skilled Soccer Players Research Articles

Variability and typical error in the kinematics and kinetics of the maximal instep kick in soccer

The purpose of this paper was to establish the variability and typical error of kinematic and kinetic variables representing the maximal instep kick in soccer for both the kicking and support legs. Ten skilled (good amateur or semi-professional) soccer players performed 20 maximal instep kicks of a stationary ball into a goal mouth. Motion of the kicking and support legs was recorded by an optoelectronic motion analysis system, and a six degrees of freedom model was used to compute kinematic and kinetic variables. Participants repeated the kicks on a second day at least 1 week later. The mean within-subject coefficient of variation across the kinematic and kinetic variables, trials, and days was 16% and did not change substantially as trial number increased or between day of test. Increasing trial number reduced the typical error (as determined by the standard error of the mean) such that for 20 trials 75% of the variables were below an arbitrary 5% threshold. It was concluded that for kicking investigations, 10–15 trials could be used and typical errors of 5% should be expected.

Capturing and testing perceptual-cognitive expertise: A comparison of stationary and movement response methods

Numerous methods have been used to study expertise and performance. In the present article, we compare the cognitive thought processes of skilled soccer players when responding to film-based simulations of defensive situations involving two different experimental conditions. Participants either remained stationary in a seated position (n = 10) or were allowed to move (n = 10) in response to life-size film sequences of 11 versus 11 open-play soccer situations viewed from a player's perspective. Response accuracy and retrospective verbal reports of thinking were collected across the two task conditions. In the movement-based response group, participants generated a greater number of verbal report statements, including a higher proportion of evaluation, prediction, and action planning statements, than did participants in the stationary group. Findings suggest that the processing strategies employed during performance differ depending on the nature of the response required of participants. Implications for behavioral methods and experimental design are discussed.

The role of movement exaggeration in the anticipation of deceptive soccer penalty kicks

Human movement containing deception about the true outcome is thought to be perceived differently compared to the non-deceptive version. Exaggeration in the movement is thought to change the perceiver's mode of functioning from an invariant to a cue-based mode. We tested these ideas by examining anticipation in skilled and less skilled soccer players while they viewed temporally occluded (-240 ms, -160 ms, -80 ms, 0 ms, +80 ms) deceptive, non-deceptive, and non-deceptive-exaggerated penalty kicks. Kinematic analyses were used to ascertain that the kicking actions differed across conditions. The accuracy of judging the direction of an opponent's kick as well as response confidence were recorded. Players were over confident when anticipating deceptive penalty kicks compared to non-deceptive kicks, suggesting a cue-based mode was used. Furthermore, there was a significant relationship between less skilled players' confidence ratings and their accuracy 80 ms before ball-foot contact in the deceptive and non-deceptive-exaggerated conditions, but not the non-deceptive condition. Because both deceptive and non-deceptive-exaggerated kicks contained exaggeration, results suggest exaggerated movements in the kickers' action at 80 ms before ball-foot contact explains why a cue-based mode prevails when anticipating deceptive kicks at this time point.

Visual span and change detection in soccer: An expertise study

There is evidence to suggest that sports experts are able to extract more perceptual information from a single fixation than novices when exposed to meaningful tasks that are specific to their field of expertise. In particular, Reingold et al. (2001) showed that chess experts use a larger visual span including fewer fixations when compared to their less skilled counterparts. The aim of the present study was to examine whether also in a more complex environment, namely soccer, skilled players use a larger visual span and fewer fixations than less skilled players when attempting to recognise players’ positions. To this end, we combined the gaze-contingent window technique with the change detection paradigm. Results seem to suggest that skilled soccer players do not use a larger visual span than less skilled players. However, skilled soccer players showed significantly fewer fixations of longer duration than their less skilled counterparts, supporting the notion that experts may extract more information from a single glance.

Identifying the processes underpinning anticipation and decision-making in a dynamic time-constrained task

A novel, representative task was used to examine skill-based differences in the perceptual and cognitive processes underlying performance on a dynamic, externally paced task. Skilled and less skilled soccer players were required to move and interact with life-size, action sequences involving 11 versus 11 soccer situations filmed from the perspective of a central defender in soccer. The ability of participants to anticipate the intentions of their opponents and to make decisions about how they should respond was measured across two separate experiments. In Experiment 1, visual search behaviors were examined using an eye-movement registration system. In Experiment 2, retrospective verbal reports of thinking were gathered from a new sample of skilled and less skilled participants. Skilled participants were more accurate than less skilled participants at anticipating the intentions of opponents and in deciding on an appropriate course of action. The skilled players employed a search strategy involving more fixations of shorter duration in a different sequential order and toward more disparate and informative locations in the display when compared with the less skilled counterparts. The skilled players generated a greater number of verbal report statements with a higher proportion of evaluation, prediction, and planning statements than the less skilled players, suggesting they employed more complex domain-specific memory representations to solve the task. Theoretical, methodological, and practical implications are discussed.

Soccer and national culture: estimating the impact of violence on 22 lads after a ball

Sports have been recently conceptualized as an effective tool for development. Questioning that argument, recent evidence suggests that the practice of soccer reveals national cultures of violence prevailing in players’ countries of origin. We model violent behaviour in the soccer pitch as a function of game specific controls as well as socioeconomic, political, cultural and conflict variables characterizing players’ home countries. We construct a database for the Latin American 2008 Libertadores Cup Competition and find that across multiple specifications and estimating techniques, only game specific variables determine sanctions to violent actions. There are three compatible explanations for this result: highly skilled soccer players may not be representative average citizens; violent conflicts may not necessarily cause a violent culture affecting all corners of society; and even when violent cultures are transmitted to individual players, those values do not condition significantly their behaviour during games. After all, sports may not be a pernicious activity that intrinsically transmits violent values to youths.

An Evaluation of End-Point Trajectory Planning during Skilled Kicking

There is evidence that actions are planned by anticipation of their external effects, with the strength of this effect being dependent on the amount of prior practice. In Experiment 1, skilled soccer players performed a kicking task under four conditions: planning in terms of an external action effect (i.e., ball trajectory) or in terms of body movements, either with or without visual error feedback. When feedback was withheld, a ball focus resulted in more accurate outcomes than a body focus. When visual feedback was allowed, there was no difference between these two conditions. In Experiment 2, both skilled and novice soccer players were tested with the addition of a control condition and in the absence of visual feedback. For both groups there was evidence that a ball focus was more beneficial for performance than a body focus, particularly in terms of movement kinematics where correlations across the joints were generally higher for body rather than ball planning. Most skilled participants reported that ball planning felt more normal than body planning. These experiments provide some evidence that actions are planned in terms of their external action effects, supporting the common-coding hypothesis of action planning.

Identifying the Critical Time Period for Information Extraction When Recognizing Sequences of Play

The authors attempted to determine the critical time period for information extraction recognizing play sequences in soccer. Although efforts have been made to identify the perceptual information underpinning such decisions, no researchers have attempted to determine when this information may be extracted from the display. The authors manipulated the duration of film sequences during the recognition phase to identify this critical time window. In an initial viewing phase, skilled soccer players watched action sequences lasting 5 s, while in a subsequent recognition phase they viewed either the entire 5-s clip or the final 3 or 1 s of each sequence. The authors predicted that for the structured viewing sequences recognition performance would be most accurate in the 3-s condition, whereas for the unstructured sequences performance was expected to become more accurate with longer exposure. The data supported the authors' predictions for the structured sequences. Skilled players were more accurate on the structured sequences in the 3-s viewing condition than the 5- (d = 1.47) or 1-s (d = 1.74) condition. No significant differences were observed between the 1- and 5-s (d = 0.23) conditions. The finding that recognition performance for structured sequences is enhanced limited to viewing only the final 3s of an attacking sequence is important in understanding expert performance and anticipation in soccer. The results supported the proposal that in soccer, and tentatively in other similar sports, structure only emerges at discrete moments preceding a critical event. Additional research is necessary to determine whether these findings generalize to other sports and even across alternative play patterns. (Contains 2 figures.)

サッカー熟練者と非熟練者の予測正確性および視覚探索方略に関する研究—1対1と3対3場面についての比較—

The present study examined the differences in anticipatory performance and visual search strategy between skilled and novice soccer players. Fifteen skilled and 10 novice soccer players participated in the experiment. Their anticipatory performance was evaluated using a temporal occlusion paradigm. Both groups looked at film clips that had been recorded on a soccer field including only one offender (1 vs. 1 situation), or three offenders and two defenders (3 vs. 3 situation). Participants were required to predict the direction of passing from the offender. Each film clip was terminated at 500ms (T1), 200ms (T2), 100ms (T3), or 0ms (T4) before, or 100ms (T5) after the ball had been passed. Skilled players showed high accuracy under T1, T2 and T3 conditions in the 3 vs. 3 situation than novice players. By using an Eyemark Record System, we tested the visual search strategy involved. The skilled players had lower search rates and longer fixation durations just before the ball was passed. These results suggest that, in comparison with novices, skilled soccer players adopt a more appropriate and effective visual search strategy, which has been acquired through experience in complex situations specific to soccer play.

FOOT AND BALL BEHAVIOR DURING IMPACT PHASE OF INSTEP SOCCER KICKING

METHODS Eleven skilled male soccer players participated in this study. They performed maximal instep kicks and two successful shots hit the target with minimal ball spin were selected from each subject. Two electrically synchronized ultra high-speed video cameras (MEMRECAM fx-6000, NAC Inc., Tokyo, Japan) located in the lateral side and backward were used. To adequately capture the foot and ball behavior during ball impact, the sampling rate of 5000 Hz was used.

Segmental dynamics of soccer instep kicking with the preferred and non-preferred leg

Detailed time-series of the resultant joint moments and segmental interactions during soccer instep kicking were compared between the preferred and non-preferred kicking leg. The kicking motions of both legs were captured for five highly skilled players using a three-dimensional cinematographic technique at 200 Hz. The resultant joint moment (muscle moment) and moment due to segmental interactions (interaction moment) were computed using a two-link kinetic chain model composed of the thigh and lower leg (including shank and foot). The mechanical functioning of the muscle and interaction moments during kicking were clearly illustrated. Significantly greater ball velocity (32.1 vs. 27.1 m · s−1), shank angular velocity (39.4 vs. 31.8 rad · s−1) and final foot velocity (22.7 vs. 19.6 m · s−1) were observed for the preferred leg. The preferred leg showed a significantly greater knee muscle moment (129.9 N · m) than the non-preferred leg (93.5 N · m), while no substantial differences were found for the interaction moment between the two legs (79.3 vs. 55.7 N · m). These results indicate that the highly skilled soccer players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg. The faster leg swing observed for the preferred leg was most likely the result of the larger muscle moment.

Attentional Focus, Dispositional Reinvestment, and Skilled Motor Performance under Pressure

Attentional processes governing skilled motor behavior were examined in two studies. In Experiment 1, field hockey players performed a dribbling task under single-task, dual-task, and skill-focused conditions under both low and high pressure situations. In Experiment 2, skilled soccer players performed a dribbling task under single-task, skill-focused, and process-goal conditions, again under low and high pressure situations. Results replicated recent findings regarding the detrimental effect of skill-focused attention and the facilitative effect of dual-task conditions on skilled performance. In addition, focusing on movement related process goals was found to adversely affect performance. Support for the predictive validity of the Reinvestment Scale was also found, with high reinvesters displaying greater susceptibility to skill failure under pressure. Results were consistent with explicit monitoring theories of choking and are further discussed in light of the conceptual distinction between explicit monitoring and reinvestment of conscious control.

Soccer

The aim of our study was to determine if any immediate changes in balance were discernable in college soccer players after a specially designed heading session. Eight male and two female skilled collegiate soccer players had a baseline balance pre‐test using the Balance Master, followed by heading 20 balls kicked consecutively by a teammate from the touchline to a point near the goal, which was followed by a post‐test using the same testing technique. Paired t‐tests were used to compare balance ability between pre‐ and post‐test conditions. There was no difference in balance pre‐ to post‐test (85.3% and 86.2% respectively). No significant difference was noted from pre‐ to post‐test in the mean equilibrium scores for conditions three through six on the Sensory Organization Test, with the exception of condition four, which revealed a significant increase from pre‐ to post‐test. We concluded that an acute session of heading soccer balls may not result in balance changes in collegiate soccer players.

Soccer

This study looks at segmental movements in the jumping header from an optimization viewpoint. Investigations on the header so far have focused on head restriction in the movement but have not clarified how and to what extent body segments influence the performance of the skill. In the present study a biomechanical model was used to analyze the jumping header in simulated competition to give a clear picture of an optimized header. Skilled soccer players headed balls at speeds of 13 m.s.‐1 the results indicated that the head moves as a free non‐restricted segment in the jumping header and should be allowed to do so, even though much soccer literature says otherwise to prevent injuries. The arm movement showed individual characteristics and gave no general advantages in optimizing ball speed after impact in the header. The movement of the legs was, on the other hand, the single most important factor in the skill. Therefore, coaches and players should focus on developing muscle strength in the stomach, back and pelvis and should put no restrictions on head and arm movement to optimize the jumping header.

Do pattern recognition skills transfer across sports? A preliminary analysis

The ability to recognize patterns of play is fundamental to performance in team sports. While typically assumed to be domain-specific, pattern recognition skills may transfer from one sport to another if similarities exist in the perceptual features and their relations and/or the strategies used to encode and retrieve relevant information. A transfer paradigm was employed to compare skilled and less skilled soccer, field hockey and volleyball players' pattern recognition skills. Participants viewed structured and unstructured action sequences from each sport, half of which were randomly represented with clips not previously seen. The task was to identify previously viewed action sequences quickly and accurately. Transfer of pattern recognition skill was dependent on the participant's skill, sport practised, nature of the task and degree of structure. The skilled soccer and hockey players were quicker than the skilled volleyball players at recognizing structured soccer and hockey action sequences. Performance differences were not observed on the structured volleyball trials between the skilled soccer, field hockey and volleyball players. The skilled field hockey and soccer players were able to transfer perceptual information or strategies between their respective sports. The less skilled participants' results were less clear. Implications for domain-specific expertise, transfer and diversity across domains are discussed.

Biomechanical differences in soccer kicking with the preferred and the non-preferred leg

The aims of this study were to examine the release speed of the ball in maximal instep kicking with the preferred and the non-preferred leg and to relate ball speed to biomechanical differences observed during the kicking action. Seven skilled soccer players performed maximal speed place kicks with the preferred and the nonpreferred leg; their movements were filmed at 400 Hz. The inter-segmental kinematics and kinetics were derived. A coefficient of restitution between the foot and the ball was calculated and rate of force development in the hip flexors and the knee extensors was measured using a Kin-Com dynamometer. Higher ball speeds were achieved with the preferred leg as a result of the higher foot speed and coefficient of restitution at the time of impact compared with the non-preferred leg. These higher foot speeds were caused by a greater amount of work on the shank originating from the angular velocity of the thigh. No differences were found in muscle moments or rate of force development. We conclude that the difference in maximal ball speed between the preferred and the non-preferred leg is caused by a better inter-segmental motion pattern and a transfer of velocity from the foot to the ball when kicking with the preferred leg.

Perceptual skill in soccer: Implications for talent identification and development

In this review, key components of perceptual skill in soccer are identified and implications for talent identification and development highlighted. Skilled soccer players can recall and recognize patterns of play more effectively than their less skilled counterparts. This ability to encode, retrieve and recognize sport-specific information is due to complex and discriminating long-term memory structures and is crucial to anticipation in soccer. Similarly, experts use their knowledge of situational probabilities (i.e. expectations) to anticipate future events. They have a better than average idea of what is likely to happen given a particular set of circumstances. Also, proficiency-related differences in visual search strategy are observed. Skilled players use their superior knowledge to control the eye movement patterns necessary for seeking and picking up important sources of information.The nature of the task plays an important role in constraining the type of search used. Skilled soccer players use different search strategies when viewing the whole field (i.e. 11 vs 11 situations) compared with micro-states of the game (i.e. 1 vs 1,3 vs 3 situations). Visual search behaviour also differs between defensive and offensive plays. These observations have implications for the development of perceptual training programmes and the identification of potential elite soccer players.

EMG activity of the iliopsoas muscle and leg kinetics during the soccer place kick

The purpose of the study was to develop a method to record intramuscular electromyogram (EMG) from the iliopsoas muscle and to relate this activity to the kinetics during the soccer place kick. Seven skilled soccer players performed 3 maximal velocity place kicks. The kicks were filmed with a high-speed camera (400 Hz) and EMG recordings were obtained from 5 muscles of the kicking leg, including wire electrodes inserted into the m. iliopsoas. The EMG signals were compared to the kinetics of the kicking leg, which were calculated from the digitised film. The results showed hardly any torque reversal about the hip joint before impact. Angular deceleration of the thigh segment did not increase the angular velocity of the shank (work -3.57 to 0.0%). M. iliopsoas was active during the entire kicking motion (average EMG 65.1-100.9%), even in the period when the thigh was decelerating. Wire electrodes can successfully be applied to EMG recordings of fast unloaded movements.

DEVELOPMENT OF PRINCIPAL MOTOR MOVEMENTS CONTROLLING BALL KICKING PERFORMANCE240

The purpose of this study was to clarify the development of principal motor movements controlling ball-kicking performance by comparing skilled soccer players with unskilled counterparts. Fifty-three skilled and sixty unskilled male college students, aged 18 to 22, were asked to perform ball-kicking as far as possible within a 30-degree fan-shaped area. The ball-kicking consisting of various movement elements was video-taped by two Hi-8 video cameras. A new version of Cause and Effect Diagram was developed to clarify a structure of ball-kicking movement qualitatively. Delphi method was applied to determine content validity of the ball-kicking movements. The ball-kicking movements in the motor process were measured by 28 movement items. Multiple regression analysis with stepwise procedure was utilized to determine criterion-related validity with various principal motor movements as the independent variables and maximum performance in ball-kicking as the dependent variable. The multiple correlation coefficient was 0.88 for the skilled player group, and 0.71 for the unskilled player group. The number of principal motor movements extracted was 9 for the skilled player group, and 6 for the unskilled. The most contributing principal movement to ball-kicking performance was inside inclination of the supporting leg in the forward-swing phase (27%) for the skilled player group, and inclination of legs in the approaching phase (46%) for the unskilled. The results indicate that the principal motor movements controlling ball-kicking performance develop corresponding to improvement in ball-kicking skill.