Miss to the Right: The Effect of Attentional Asymmetries on Goal-Kicking

Cerebral asymmetries for spatial attention generate a bias of attention – causing lines to be bisected to the left or right in near (within reach) and far (outside reach) space, respectively. This study explored whether the rightward deviation for bisecting lines in far space extends to tasks where a ball is aimed between two goal-posts. Kicking was assessed in a laboratory and a real-life setting. In the laboratory setting, 212 participants carried out three conditions: (a) kick a soccer ball at a single goal post, (b) kick a soccer ball between two goal posts and (c) use a stick to indicate the middle between two goal posts. The goals were placed at a distance of 4.0 m. There was no deviation in the one-goal kicking condition – demonstrating that no asymmetries exist in the perceptual motor system when aiming at a single point. When kicking or pointing at the middle between two goal posts, rightward deviations were observed. In the real-world setting, the number of misses to the left or right of goal (behinds) in the Australian Rules football for the 2005–2009 seasons was assessed. The data showed more rightward deviations for kicks at goal. Combined, the studies suggest that the rightward deviation for lines placed in far space extends to the kicking of a football in laboratory and real-life settings. This asymmetry in kicking builds on a body of research showing that attentional asymmetries impact everyday activities.     

Eccentric utilization ratio: effect of sport and phase of training

The eccentric utilization ratio (EUR), which is the ratio of countermovement jump (CMJ) to static jump (SJ) performance, has been suggested as a useful indicator of power performance in athletes. The purpose of the study was to compare the EUR of athletes from a variety of different sports and during different phases of training. A total of 142 athletes from rugby union, Australian Rules Football, soccer, softball, and field hockey were tested. Subjects performed both CMJ and SJ on a force plate integrated with a position transducer. The EUR was measured as the ratio of CMJ to SJ for jump height and peak power. The rugby union, Australian Rules Football, and hockey athletes were tested during off-season and preseason to provide EUR data during different phases of training. For men, EUR for soccer, Australian Rules Football, and rugby was greater than softball (effect size range, 0.83-0.92). For women, EUR for soccer was greater than field hockey and softball (0.86- 1.0). There was a significant difference between the jump height and peak power method for the Australian Rules Football, rugby, and field hockey tests conducted preseason (p < 0.05). For field hockey, there was a significant increase in EUR from off-season to preseason. Athletes in sports such as soccer, rugby union, and Australian Rules Football appear to have higher EUR values, which reflects the greater reliance on stretch shortening activities in these sports. It does appear that EUR can be used to track changes in training with the values significantly increasing from off-season to preseason. The EUR provides the practitioner with information about the performance of athletes and appears to be sensitive to changes in the type of training being undertaken.     

Evaluation of a composite test of kicking performance

The aim of this study was to evaluate the reliability and sensitivity of variables for the direct assessment of kicking performance in young soccer players. One hundred and six elite young soccer players were divided into 4 age groups (12-15 years). Absolute error (AE), variable error (VE), and constant error (CE) were evaluated as the variables of kicking accuracy, whereas the kicking velocity variables involved the maximum ball velocity (BVmax) and the ball velocity during accurate kicks (BVacc). Results suggested low-to-moderate reliability of the kicking accuracy (intraclass correlation coefficient [ICC] = 0.00-0.67) and high reliability of the kicking velocity variables (ICC = 0.87-0.94). Regarding the sensitivity, most of the variables detected the differences both between the dominant and nondominant legs and among the age groups. Because the evaluated variables should have a property of face validity, the findings obtained generally suggest that AE (and perhaps VE, as the measures of kicking accuracy) and both BVmax and BVacc (as the measures of kicking velocity) could be used within a routine composite test of kicking performance in young elite soccer players. Further development of the evaluated composite test of kicking performance could be based on the involvement of other kicking techniques and on testing the athletes of different ages, levels of skill, or sport specialization.     

The influence of joint rigidity on impact efficiency and ball velocity in football kicking

Executing any skill with efficiency is important for performance. In football kicking, conflicting and non-significant results have existed between reducing ankle plantarflexion during foot-ball contact with impact efficiency, making it unclear as to its importance as a coaching instruction. The aims of this study were to first validate a mechanical kicking machine with a non-rigid ankle, and secondly compare a rigid to a non-rigid ankle during the impact phase of football kicking. Measures of foot-ball contact for ten trials per ankle configuration were calculated from data recorded at 4000 Hz and compared. The non-rigid ankle was characterised by initial dorsiflexion followed by plantarflexion for the remainder of impact, and based on similarities to punt and instep kicking, was considered valid. Impact efficiency (foot-to-ball speed ratio) was greater for the rigid ankle (rigid = 1.16 ± 0.02; non-rigid = 1.10 ± 0.01; p < 0.001). The rigid ankle was characterised by significantly greater effective mass and significantly less energy losses. Increasing rigidity allowed a greater portion of mass from the shank to be used during the collision. As the ankle remained in plantarflexion at impact end, stored elastic energy was not converted to ball velocity and was considered lost. Increasing rigidity is beneficial for increasing impact efficiency, and therefore ball velocity.     

Relationships between isokinetic knee strength, single-sprint performance, and repeated-sprint ability in football players

Previous research has demonstrated that muscular strength of the knee extensors is related to the speed an athlete can produce during a single-sprint performance. Football players, as well as many other athletes on the field and the court, execute multiple sprints during the course of a match. The purpose of this study was to examine the relationships between leg strength, single-sprint speed, and repeated-sprint ability. Thirty-eight football players from 3 codes (soccer, rugby league, rugby union) completed a 12- x 20-m repeated-sprint protocol and were evaluated for peak isokinetic knee extension and flexion torque at 60 degrees .s(-1), 150 degrees .s(-1), and 240 degrees .s(-1). Although single-sprint performance correlated with peak extensor and flexor torque at all velocities, the strongest correlation was observed between relative knee extensor torque at 240 degrees .s(-1) and the initial acceleration phase (0-10 m) of the single-sprint performance (r = -0.714, p < 0.01). However, the data suggest that factors other than strength contribute to repeated-sprint ability. This finding provides new evidence in elucidating the relationship between strength and repeated-sprint performance.     

Validity and reliability of agility tests in junior Australian football players

Young, W, Farrow, D, Pyne, D, McGregor, W, and Handke, T. Validity and reliability of agility tests in junior Australian football players. J Strength Cond Res 25(12): 3399-3403, 2011-The importance of sport-specific stimuli in reactive agility tests (RATs) compared to other agility tests is not known. The purpose of this research was to determine the validity and reliability of agility tests. Fifty junior Australian football players aged 15-17 years, members of either an elite junior squad (n = 35) or a secondary school team (n = 15), were assessed on a new RAT that involved a change of direction sprint in response to the movements of an attacking player projected in life size on a screen. These players also underwent the planned Australian Football League agility test, and a subgroup (n = 13) underwent a test requiring a change of direction in response to a left or right arrow stimulus. The elite players were significantly better than the school group players on the RAT (2.81 ± 0.08 seconds, 3.07 ± 0.12 seconds; difference 8.5%) but not in the arrow stimulus test or planned agility test. The data were log transformed and the reliability of the new RAT estimated using typical error (TE) expressed as a coefficient of variation. The TE for the RAT was 2.7% (2.0-4.3, 90% confidence interval) or 0.07 seconds (0.5-1.0), with an intraclass correlation coefficient (ICC) of 0.33. For the test using the arrow stimulus, the TE was 3.4% (2.4-6.2), 0.09 (0.06-0.15) seconds, and ICC was 0.10. The sport-specific stimulus provided by the new RAT is a crucial component of an agility test; however, adoption of the new RAT for routine testing is likely to require more accessible equipment and several familiarization trials to improve its reliability.     

Hamstring muscle kinematics and activation during overground sprinting

Hamstring muscle strain injury is one of the most commonly seen injuries in sports such as track and field, soccer, football, and rugby. The purpose of this study was to advance our understanding of the mechanisms of hamstring muscle strain injuries during over ground sprinting by investigating hamstring muscle-tendon kinematics and muscle activation. Three-dimensional videographic and electromyographic (EMG) data were collected for 20 male runners, soccer or lacrosse players performing overground sprinting at their maximum effort. Hamstring muscle-tendon lengths, elongation velocities, and linear envelop EMG data were analyzed for a running gait cycle of the dominant leg. Hamstring muscles exhibited eccentric contractions during the late stance phase as well as during the late swing phase of overground sprinting. The peak eccentric contraction speeds of the hamstring muscles were significantly greater during the late swing phase than during the late stance phase (p=0.001) while the hamstring muscle-tendon lengths at the peak eccentric contraction speeds were significantly greater during the late stance phase than during the late swing phase (p=0.001). No significant differences existed in the maximum hamstring muscle-tendon lengths between the two eccentric contractions. The potential for hamstring muscle strain injury exists during the late stance phase as well as during the late swing phases of overground sprinting.     

Performance and reference data in the jump squat at different relative loads in elite sprinters,rugby players,and soccer players

The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n = 62), rugby players (n = 32), and soccer players (n = 32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes’ body mass (BM), and a load of 10% of BM was gradually added until a clear decrement in the bar power was observed. Comparisons of bar variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar velocity, force, and power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40–110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (%BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive, and peak velocity) for sprinters, rugby players, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.     

Visual Search Strategies of Soccer Players Executing a Power vs. Placement Penalty Kick

Introduction

When taking a soccer penalty kick, there are two distinct kicking techniques that can be adopted; a ‘power’ penalty or a ‘placement’ penalty. The current study investigated how the type of penalty kick being taken affected the kicker’s visual search strategy and where the ball hit the goal (end ball location).

Method

Wearing a portable eye tracker, 12 university footballers executed 2 power and placement penalty kicks, indoors, both with and without the presence of a goalkeeper. Video cameras were used to determine initial ball velocity and end ball location.

Results

When taking the power penalty, the football was kicked significantly harder and more centrally in the goal compared to the placement penalty. During the power penalty, players fixated on the football for longer and more often at the goalkeeper (and by implication the middle of the goal), whereas in the placement penalty, fixated longer at the goal, specifically the edges. Findings remained consistent irrespective of goalkeeper presence.

Discussion/conclusion

Findings indicate differences in visual search strategy and end ball location as a function of type of penalty kick. When taking the placement penalty, players fixated and kicked the football to the edges of the goal in an attempt to direct the ball to an area that the goalkeeper would have difficulty reaching and saving. Fixating significantly longer on the football when taking the power compared to placement penalty indicates a greater importance of obtaining visual information from the football. This can be attributed to ensuring accurate foot-to-ball contact and subsequent generation of ball velocity. Aligning gaze and kicking the football centrally in the goal when executing the power compared to placement penalty may have been a strategy to reduce the risk of kicking wide of the goal altogether.     

The effects of resisted sprint training on acceleration performance and kinematics in soccer, rugby union, and Australian football players

Acceleration is a significant feature of game-deciding situations in the various codes of football. However little is known about the acceleration characteristics of football players, the effects of acceleration training, or the effectiveness of different training modalities. This study examined the effects of resisted sprint (RS) training (weighted sled towing) on acceleration performance (0-15 m), leg power (countermovement jump [CMJ], 5-bound test [5BT], and 50-cm drop jump [50DJ]), gait (foot contact time, stride length, stride frequency, step length, and flight time), and joint (shoulder, elbow, hip, and knee) kinematics in men (N = 30) currently playing soccer, rugby union, or Australian football. Gait and kinematic measurements were derived from the first and second strides of an acceleration effort. Participants were randomly assigned to 1 of 3 treatment conditions: (a) 8-week sprint training of two 1-h sessions x wk(-1) plus RS training (RS group, n = 10), (b) 8-week nonresisted sprint training program of two 1-h sessions x wk(-1) (NRS group, n = 10), or (c) control (n = 10). The results indicated that an 8-week RS training program (a) significantly improves acceleration and leg power (CMJ and 5BT) performance but is no more effective than an 8-week NRS training program, (b) significantly improves reactive strength (50DJ), and (c) has minimal impact on gait and upper- and lower-body kinematics during acceleration performance compared to an 8-week NRS training program. These findings suggest that RS training will not adversely affect acceleration kinematics and gait. Although apparently no more effective than NRS training, this training modality provides an overload stimulus to acceleration mechanics and recruitment of the hip and knee extensors, resulting in greater application of horizontal power.     

Evaluation of the reliability of soccer-specific field tests

The soccer-specific field tests are popular among coaches due to their simplicity, validity, and minimal use of equipment. Nevertheless, there is a general lack of data about their reliability, particularly regarding the tests of anaerobic performance. Twenty professional male soccer players performed 3 consecutive trials of the tests of throwing-in and standing-kick performance (the distance measured) as well as on timed 10-m sprint, flying 20-m sprint, running 10 x 5 m, zigzag running with and without the ball, and the skill index (i.e., the ratio of the zigzag running without and with the ball). With the exception of the throwing-in and standing kick, the evaluated tests revealed high intraclass correlation coefficients (i.e., >0.80), small within-individual variations (coefficient of variation, <4%), and sample sizes for detecting a 2% change in the tested performance that are either close to or below the standard size of a professional soccer squad. In addition to simplicity and face validity, most of the evaluated tests revealed high reliability. Therefore, the evaluated tests are recommended for sport-specific profiling and early selection of young athletes as well as for routine testing procedures that could detect effects of various intervention procedures. Regarding the throwing-in and standing-kick tests, direct measurement of the ball velocity (e.g., with a standard radar gun) is recommended.     

Perceived importance of weight training to selected NCAA Division III men and women student-athletes

The purpose of this study was to examine differences in perception of the importance of weight training as a part of general and sport-specific training for selected collegiate men and women student-athletes. Subjects included 139 men and 165 women varsity National Collegiate Athletic Association Division III student-athletes who participated in the following sports: baseball, basketball, field hockey, football, lacrosse, soccer, softball, swimming, tennis, track & field, or volleyball. Men student-athletes were significantly more likely to consider weight training essential to their general and sport-specific training than women student-athletes, as measured by the Training Information Survey. Additionally, men student-athletes were found to be significantly more competitive and win-oriented than women student-athletes (p < 0.001) as measured by the Sport Orientation Questionnaire, which is consistent with previous research. Results also showed that only highly goal-oriented student-athletes perceived weight training as: (a) important to both men and women and (b) having both feminine and masculine traits. It was concluded that significant gender differences exist in the perceived importance of weight training and that the constructs of competitiveness, win and goal orientation, may influence a student-athlete's perception of the importance of weight training. Coaches of both men and women student-athletes must teach that weight training is important for female and male student-athletes.     

Analysis of Biomechanical Characteristics of Football Players at Different Levels Kicking with the Inner Edge of Instep

This study aims to analyze the difference in biomechanical properties of football players at different levels when kicking the football with the inner edge of the instep. Before the experiment, ten football players were selected; five were higher than the national level (group A), and the other five players were lower than the national level II (group B). During the experiment, the motion process was captured by a high-speed camera for biomechanical analysis. It was found that in group A, the thigh and leg swung in less time and larger amplitude, the acceleration of backswing and forward swing of the leg was larger, and the angular velocity of forward swing was also larger. At the moment of touching the ball, in the sagittal plane, the ankle joint angle and angular velocity of group A were larger than those of group B (P < 0.05). In conclusion, the high-level athletes can complete the high-quality kicking through a larger swing amplitude and speed of the kicking leg. In the training process, the athletes should pay attention to the speed and strength of the kicking leg to improve the kicking level.     

Force-velocity relationship and maximal power on a cycle ergometer. Correlation with the height of a vertical jump

The force-velocity relationship on a Monark ergometer and the vertical jump height have been studied in 152 subjects practicing different athletic activities (sprint and endurance running, cycling on track and/or road, soccer, rugby, tennis and hockey) at an average or an elite level. There was an approximately linear relationship between braking force and peak velocity for velocities between 100 and 200 rev.min-1. The highest indices of force P0, velocity V0 and maximal anaerobic power (Wmax) were observed in the power athletes. There was a significant relationship between vertical jump height and Wmax related to body mass.     

A joint kinetic analysis of rugby place kicking technique to understand why kickers achieve different performance outcomes

We aimed to identify differences in kicking leg and torso mechanics between groups of rugby place kickers who achieve different performance outcomes, and to understand why these features are associated with varying levels of success. Thirty-three experienced place kickers performed maximum effort place kicks, whilst three-dimensional kinematic (240 Hz) and ground reaction force (960 Hz) data were recorded. Kicking leg and torso mechanics were compared between the more successful (‘long’) kickers and two sub groups of less successful kickers (’short’ and ‘wide-left’) using magnitude-based inferences and statistical parametric mapping. Short kickers achieved substantially slower ball velocities compared with the long kickers (20.8 ± 2.2 m/s vs. 27.6 ± 1.7 m/s, respectively) due to performing substantially less positive hip flexor (normalised mean values = 0.071 vs. 0.092) and knee extensor (0.004 vs. 0.009) joint work throughout the downswing, which may be associated with their more front-on body orientation, and potentially a lack of strength or intent. Wide-left kickers achieved comparable ball velocities (26.9 ± 1.6 m/s) to the long kickers, but they were less accurate due to substantially more longitudinal ball spin and a misdirected linear ball velocity. Wide-left kickers created a tension arc across the torso and therefore greater positive hip flexor joint work (normalised mean = 0.112) throughout the downswing than the long kickers. Whilst this may have assisted kicking foot velocity, it also induced greater longitudinal torso rotation during the downswing, and may have affected the ability of the hip to control the direction of the foot trajectory.     

Theoretical study of factors affecting ball velocity in instep soccer kicking

The objective of this study was to investigate the factors affecting ball velocity at the final instant of the impact phase (t1) in full instep soccer kicking. Five experienced male university soccer players performed maximal full instep kicks for various foot impact points using a one-step approach. The kicking motions were captured two dimensionally by a high-speed camera at 2,500 fps. The theoretical equation of the ball velocity at t1 given in the article was derived based on the impact dynamics theory. The validity of the theoretical equation was verified by comparing the theoretical relationship between the impact point and the ball velocity with the experimental one. Using this theoretical equation, the relationship between the impact point and the ball velocity was simulated. The simulation results indicated that the ball velocity is more strongly affected by the foot velocity at the initial instant of the impact phase than by other factors. The simulation results also indicated that decreasing the ankle joint reaction force during ball impact shifts the impact point that produces the greatest ball velocity to the toe side and decreasing the ankle joint torque during ball impact shifts the impact point that produces the greatest ball velocity to the ankle side.     

Effective speed and agility conditioning methodology for random intermittent dynamic type sports

Different coaching methods are often used to improve performance. This study compared the effectiveness of 2 methodologies for speed and agility conditioning for random, intermittent, and dynamic activity sports (e.g., soccer, tennis, hockey, basketball, rugby, and netball) and the necessity for specialized coaching equipment. Two groups were delivered either a programmed method (PC) or a random method (RC) of conditioning with a third group receiving no conditioning (NC). PC participants used the speed, agility, quickness (SAQ) conditioning method, and RC participants played supervised small-sided soccer games. PC was also subdivided into 2 groups where participants either used specialized SAQ equipment or no equipment. A total of 46 (25 males and 21 females) untrained participants received (mean +/- SD) 12.2 +/- 2.1 hours of physical conditioning over 6 weeks between a battery of speed and agility parameter field tests. Two-way analysis of variance results indicated that both conditioning groups showed a significant decrease in body mass and body mass index, although PC achieved significantly greater improvements on acceleration, deceleration, leg power, dynamic balance, and the overall summation of % increases when compared to RC and NC (p < 0.05). PC in the form of SAQ exercises appears to be a superior method for improving speed and agility parameters; however, this study found that specialized SAQ equipment was not a requirement to observe significant improvements. Further research is required to establish whether these benefits transfer to sport-specific tasks as well as to the underlying mechanisms resulting in improved performance.     

Évaluation lymphoscintigraphique d’éventuelles anomalies du système lymphatique au niveau des membres inférieurs de joueurs de football : à propos de six observations

In order to demonstrate possible abnormalities of the lymphatic system as consequence of soccer practice, lymphoscintigraphic investigations of the lower limbs have been performed (1) in five young male volunteers with at least ten years of soccer practice (kicking with one foot in the five cases; previous osteoarticular events involving the ankles in four: no clinical edema observed) and (2) in one professional female soccer player (also kicking with one foot) who presented with one bilateral distal edema of the lower limbs. After the subcutaneous injection of ^99mTc-labeled HSA nanosized colloids in the first interdigital space of the feet and the limbs being at rest during 30 min, the tracer did reach normally the first inguinal nodes in only three subjects (their kicking limbs), suggesting thus one functional insufficiency of the lymphatic system at the level of nine of the twelve limbs. With exercise (tip-toeing during 5 min), one (abnormal) functional asymmetry (activity reaching the inguinal nodes greater at the level of the kicking limb than at the level of the not-kicking one) was also observed. Finally, the female player with distal limb edemas showed at the end of the investigation the lowest values (within the group) of tracer disappearance at the level of the injection sites. Morphological abnormalities on the lymphatic system of the lower limbs (as dermal backflow, lymphostasis, …) were observed in none of the subjects at the end of the investigation, suggesting lesions at the level of the tissues injected and/or of the initial lymphatics of the feet rather than lesions at the level of the great lymphatic vessels of the limbs. To conclude and although based on a limited series of subjects, the results suggest the development of functional lymphatic abnormalities at the level of the feet in soccer players, abnormalities mostly without clinical manifestations but that can lead to clinically obvious edemas. These abnormalities would have to be confirmed on a larger series.     

The dominant leg is more likely to get injured in soccer players: systematic review and meta-analysis

In soccer (football), dominant limb kicking produces higher ball velocity and is used with greater frequency than the non-dominant limb. It is unclear whether limb dominance has an effect on injury incidence. The purpose of this systematic review with meta-analysis is to examine the relationship between limb dominance and soccer injuries. Studies were identified from four online databases according to PRISMA guidelines to identify studies of soccer players that reported lower extremity injuries by limb dominance. Relevant studies were assessed for inclusion and retained. Data from retained studies underwent meta-analyses to determine relative risk of dominant versus non-dominant limb injuries using random-effects models. Seventy-four studies were included, with 36 of them eligible for meta-analysis. For prospective lower extremity injury studies, soccer players demonstrated a 1.6 times greater risk of injury to the dominant limb (95% CI [1.3–1.8]). Grouped by injury location, hamstring (RR 1.3 [95% CI 1.1–1.4]) and hip/groin (RR 1.9 [95% CI 1.3–2.7]) injuries were more likely to occur to the dominant limb. Greater risk of injury was present in the dominant limb across playing levels (amateurs RR 2.6 [95% CI 2.1–3.2]; youths RR 1.5 [95% CI 1.26–1.67]; professionals RR 1.3 [95% CI 1.14–1.46]). Both males (RR 1.5 [95% CI 1.33–1.68)] and females (RR 1.5 [95% CI 1.14–1.89]) were more likely to sustain injuries to the dominant limb. Future studies investigating soccer injury should adjust for this confounding factor by using consistent methods for assigning limb dominance and tracking use of the dominant versus non-dominant limb.