Search

The neural circuitry and biomechanics of kicking in locusts have been studied to understand their roles in the control of both kicking and jumping. It has been hypothesized that the same neural circuit and biomechanics governed both behaviors but this hypothesis was not testable with current technology. We built a neuromechanical model to test this and to gain a better understanding of the role of the semi-lunar process (SLP) in jump dynamics. The jumping and kicking behaviors of the model were tested by comparing them with a variety of published data, and were found to reproduce the results from live animals. This confirmed that the kick neural circuitry can produce the jump behavior. The SLP is a set of highly sclerotized bands of cuticle that can be bent to store energy for use during kicking and jumping. It has not been possible to directly test the effects of the SLP on jump performance because it is an integral part of the joint, and attempts to remove its influence prevent the locust from being able to jump. Simulations demonstrated that the SLP can significantly increase jump distance, power, total energy and duration of the jump impulse. In addition, the geometry of the joint enables the SLP force to assist leg flexion when the leg is flexed, and to assist extension once the leg has begun to extend. [ABSTRACT FROM AUTHOR]

Copyright of RICYDE. Revista Internacional de Ciencias del Deporte is the property of Revista Internacional de Ciencias del Deporte and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Even though the importance of artificial soccer turf systems is increasing, the interaction of players with different surface systems during movements specific to soccer is not well understood. As the behaviour of the supporting leg might be crucial for the success of kicks at goal, the purpose of this study was to investigate the movement of the whole body and the supporting leg when kicking at goal on one type of natural turf and two different types of artificial soccer turf. Four synchronized high speed cameras were used to record the movements of 17 players when kicking at goal. The type of surface systems significantly influenced the kicking speed, accuracy, foot eversion of the supporting leg and player comportment during deceleration over the last step before ball contact. Difficulties in controlling the lower leg motion on one certain type of artificial turf might be the reason for variations and kicking performance. [ABSTRACT FROM AUTHOR]

Abstract: The RoboCup community has one definite goal [H. Kitano, M. Asada, RoboCup humanoid challenge: That’s one small step for a robot, one giant leap for mankind, in: IEEE/RSJ Int. Conf. on Intelligent Robots and Systems, IROS1998, Victoria, pp. 419–424, 1998]: winning against the human world soccer champion team by the year 2050. This implies real tackles and fouls between humans and robots, rising safety concerns for the robots and even more important for the human players. Nowadays, similar questions are discussed in the field of physical human–robot interaction (pHRI), but mainly in the context of industrial and service robotics applications. The first part of our paper is an attempt for a pHRI view on human–robot soccer. We take scenes from real soccer matches and discuss what could have happened if one of the teams consisted of robots instead of humans. The most important result is that elastic joints are needed to reduce the impact during collisions. The second and third part consider conversely, how the robot can handle the impact of kicking the ball and how it can reach the velocity of human-level soccer. Again joint elasticity is the key point. Overall, the paper analyzes a vision far ahead. However, all our conclusions are based on concrete simulations, experiments, derivations, or findings from sports science, forensics, and pHRI. [Copyright &y& Elsevier]

Collision modeling and control are important aspects of simulation of many human and robotic tasks. A scientific inquiry into a foot-ball collision is made in this paper from the perspective of dynamics, control, modeling, and simulation. As an extension of the Hertzian contact model, our generalized compliant collision model with nonlinear elasticity and damping is tested by a human lower limb kicking a soccer ball. The experiment-based elasticity is used to model the energy transfer of the foot-ball collision and overcome some problems caused by impulse impact modeling. The nonlinear damping in proportion to a restitution-related constant eliminates impact discontinuity. A robust sliding mode controller is developed to track the preplanned trajectory against modeling uncertainties and impact disturbances. The collision duration (about 0.014 s), the ball departure velocity (31.83 m/s), the average foot-ball collision force (about 975.5 N), and the ball peak deformation (about 0.079 m) obtained by simulation match the reported results. The observed three, phases of the foot-ball collision are confirmed by our simulation, and the ‘follow-through’ phenomenon in sports is demonstrated. [ABSTRACT FROM AUTHOR]

The article focuses on the study about the biomechanical characteristics and determinants of instep soccer kick. Researchers conclude that understanding the biomechanics of soccer kicking is particularly important for guiding and monitoring the training process. Results show that powerful kicks are achieved through a high foot velocity and coefficient of restitution. Preliminary data indicate that accurate kicks are achieved through slower kicking motion and ball speed values.

To investigate non-kicking-side arm motion during rugby place kicking, five experienced male kickers performed trials under two conditions, both with an accuracy requirement but one with an additional maximal distance demand. Joint centre coordinates were obtained at 120 Hz during kicking trials and a three-dimensional model was created to enable the determination of segmental contributions to whole-body angular momentum. All kickers possessed minimal non-kicking-side arm angular momentum about the global medio-lateral axis. The more accurate kickers exhibited greater non-kicking-side arm angular momentum about the global antero-posterior axis. This augmented the whole-body antero-posterior angular momentum, and altered the whole-body lateral lean at ball contact. The accurate kickers also exhibited greater non-kicking-side arm angular momentum about the global longitudinal axis, which opposed the kicking leg longitudinal angular momentum and attenuated the whole-body longitudinal angular momentum. All participants increased the longitudinal angular momentum of the non-kicking-side arm in the additional distance demand condition, except for one participant whose accuracy decreased, suggesting that the longitudinal angular momentum of the non-kicking-side arm assists maintenance of accuracy in maximum distance kicking. Goal kickers should be encouraged to produce non-kicking-side arm rotations about both the antero-posterior and longitudinal axes, as these appear important for both the initial achievement of accuracy, and for maintaining accuracy during distance kicking. [ABSTRACT FROM AUTHOR]

The kicking action predominantly used in Australian Rules football is considered to be responsible for many lower limb injuries. The aim of this study was to describe a non-invasive method of identifying the thigh muscles involved in kicking an Australian Rules football, using MRI. Both upper thighs of 10 recreational footballers were examined using a 1.5-T General Electric MRI scanner before and immediately after carrying out a set kicking exercise protocol. The signal intensity (SI) changes in 14 individual muscles were investigated using a standardized region of interest to determine the levels of muscle activity. Significant SI changes were observed in several muscles of the kicking and stance legs among all participants. In the kicking leg, the greatest SI changes were observed in the adductor longus and tensor fascia latae muscles (49.38% (±8.95) and 45.47% (±7.91), respectively; P < 0.05), whereas in the stance leg, the muscles displaying the highest changes were the semitendinosus and tensor fascia latae muscles (46.48% (±9.97) and 33.68% (±8.36), respectively; P < 0.05). This study has shown that MRI can be useful for observing the activity of individual muscles in the upper thigh during the kicking motion. This non-invasive approach provides a detailed analysis of anatomy and emphasizes the muscles at high risk of injury. [ABSTRACT FROM AUTHOR]

We investigated the escape jumps that locusts produce in response to approaching objects. Hindleg muscular activity during an escape jump is similar to that during a defensive kick. Locusts can direct their escape jumps up to 50° either side of the direction of their long axis at the time of hindleg flexion, allowing them to consistently jump away from the side towards which an object is approaching. Variation in jump trajectory is achieved by rolling and yawing movements of the body that are controlled by the fore- and mesothoracic legs. During hindleg flexion, a locust flexes the foreleg ipsilateral to its eventual jump trajectory and then extends the contralateral foreleg. These foreleg movements continue throughout co-contraction of the hindleg tibial muscles, pivoting the locust’s long axis towards its eventual jump trajectory. However, there are no bilateral differences in the motor programs of the left and right hindlegs that correlate with jump trajectory. Foreleg movements enable a locust to control its jump trajectory independent of the hindleg motor program, allowing a decision on jump trajectory to be made after the hindlegs have been cocked in preparation for a jump. [ABSTRACT FROM AUTHOR]

Background and Purpose. Infants born preterm differ in their spontaneous kicking, as well as their learning and memory abilities in the mobile paradigm, compared with infants born full-term. In the mobile paradigm, a supine infant's ankle is tethered to a mobile so that leg kicks cause a proportional amount of mobile movement. The purpose of this study was to investigate the relative kicking frequency of the tethered (right) and nontethered (left) legs in these 2 groups of infants. Subjects. Ten infants born full-term and 10 infants born preterm (>33 weeks gestational age, >2,500 g) and 10 comparison infants participated in the study. Methods. The relative kicking frequencies of the tethered and nontethered legs were analyzed during learning and short-term and long-term memory periods of the mobile paradigm. Results. Infants born full-term showed an increase in the relative kicking frequency of the tethered leg during the learning period and the short-term memory period but not for the long-term memory period. Infants born preterm did not show a change in kicking pattern for learning or memory periods, and consistently kicked both legs in relatively equal amounts. Discussion and Conclusion. Infants born full-term adapted their baseline kicking frequencies in a task-specific manner to move the mobile and then retained this adaptation for the short-term memory period. In contrast, infants born preterm showed no adaptation, suggesting a lack of purposeful leg control. This lack of control may reflect a general decrease in the ability of infants born preterm to use their limb movements to interact with their environment. As such, the mobile paradigm may be clinically useful in the early assessment and intervention of infants born preterm and at risk for future impairment. [Heathcock JC, Bhat AN, Lobo MA, Galloway JC. The relative kicking frequency of infants born full-term and preterm during learning and short-term and long-term memory periods of the mobile p... [ABSTRACT FROM AUTHOR]

The kinematics of swimming frogs have been studied extensively in the past and, based on these results, hypotheses regarding the hydrodynamics of frog swimming can be generated. To test these hypotheses we used digital particle image velocimetry (DPIV) to quantify the flow structure of the wake produced by the feet during the propulsion phase of the kick of surface swimming frogs (Rana pipiens). These frogs use two different gaits, asynchronous and synchronous kicking, and the magnitude of the thrust produced by the feet differs between asynchronous (34±5.4 mN foot-1) and synchronous kicking (71±13.3 mN foot-1), as does maximum swimming speed, with higher swimming speed and forces produced during the synchronous kicks. Previous studies have suggested that an interaction between the feet, resulting in a single posteriorly directed fluid jet, as the feet come together at the end of synchronous kicks, may augment force production. Our results show, however, that each foot produces its own distinct vortex ring, in both asynchronous and synchronous kicking of the feet. There is no evidence of a central jet being produced even during powerful synchronous kicks (maximum thrust calculated was 264 mN foot-1). An alternative mechanism of force production could be the lift-based paddling recently suggested for delta-shaped feet of swimming birds. However, the orientation of the vortex rings generated by the feet Is almost perpendicular to the swimming direction for both gaits and there is only a slight asynchrony of the shedding of the distal (start) and proximal (stop) vortex rings, which is different from what would be expected by a dominantly lift-based mechanism. Thus, our results do not support lift as a major mechanism contributing to thrust. Instead, our data support the hypothesis that propulsion is based on drag and acceleration reaction forces where the thrust is generated by separated, but attached, vortex rings on the suction side of the feet, resulting in vortices that are shed behind the frogs during both asynchronous and synchronous kicking. [ABSTRACT FROM AUTHOR]

Background and Purpose. By 3 to 4 months of age, infants born full-term and without known disease display associative learning and memory abilities in the mobile paradigm, where an infant's leg is tethered to a mobile such that leg kicks result in proportional mobile movement. The first purpose of this study was to examine the learning and memory abilities of a group of infants born full-term compared with those of a comparison group. Little is known about the learning and memory abilities in infants born preterm, a group at known risk for future impairments in learning and movement. The second purpose of this study was to determine if and when an age-adjusted group of infants born prematurely display associative learning and memory abilities over a 6-week period. Subjects. Ten infants born full-term (38-42 weeks gestational age [GA]) and 10 infants born preterm (<33 weeks GA and <2,500 g) who were tethered and had control over the mobile movement were independently compared with a comparison group of 10 infants born full-term who were tethered and viewed a moving mobile but did not have control over the mobile movement. Infants in all 3 groups were seen at 3 to 4 months of age and were excluded from participation for any known visual or orthopedic diagnoses. Methods. Infants were tested using the mobile conjugate reinforcement paradigm, where one leg is tethered to an overhead mobile such that kicking with that leg results in proportional mobile movement. The kicking rates of the full-term group and the preterm group were compared with their own initial (baseline) kicking rates and with those of the comparison group. Results. After exposure to the conjugate relationship between kicking and mobile movement, the full-term group kicked more frequently compared with their own baseline levels and compared with the comparison group, fulfilling both criteria for learning and memory. In contrast, the preterm group did not... [ABSTRACT FROM AUTHOR]

We propose a hierarchical retrieval system where shape, color and motion characteristics of the human body are captured in compressed and uncompressed domains. The proposed retrieval method provides human detection and activity recognition at different resolution levels from low complexity to low false rates and connects low level features to high level semantics by developing relational object and activity presentations. The available information of standard video compression algorithms are used in order to reduce the amount of time and storage needed for the information retrieval. The principal component analysis is used for activity recognition using MPEG motion vectors and results are presented for walking, kicking, and running to demonstrate that the classification among activities is clearly visible. For low resolution and monochrome images it is demonstrated that the structural information of human silhouettes can be captured from AC-DCT coefficients. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

In this review, we explore the role of motor control and biomechanics in developing an understanding of soccer skills using kicking as the main vehicle. The links between these sub-disciplines of sport science have not been well established in the past because of an emphasis on cognitive processes in traditional accounts of motor behaviour. We argue that a dynamical systems interpretation of the processes of coordination and control in movements with multiple degrees of freedom signals a new era in the relationship between the sub-disciplines of motor control and biomechanics. Although research on coordination and control of soccer skills is currently sparse, there are indications that the relationship between motor control and biomechanics could form a significant component of scientific programmes in talent identification and skill development. Further interdisciplinary work is needed to enhance understanding of coordination and control of soccer skills. [ABSTRACT FROM AUTHOR]

Fetal movement has always been considered an essential indicator to evaluate the health of the unborn fetus. Many factors affect fetal movement. The frequency of fetal kicking is an important measurement of whether fetal development is progressing and healthy. Various instruments and methods of detecting fetal movement have been used and each method has its advantages and disadvantages. Although limited by the fetal environment in utero, the finite element method and musculoskeletal model can be used to calculate fetal lower limb movement. This review aims to summarize the current detection techniques for fetal movement, especially in the lower limbs. These will be outlined by describing the different measurements of fetal movement, and the related biomechanical analyses of fetal lower limb skeletogenesis and the associated muscular development to better evaluate and calculate the movements of the fetus in the womb.

Fast unloaded movements (i.e. striking, throwing and kicking) are typically performed in a proximo-distal sequence, where initially high proximal segments accelerate while distal segments lag behind, after which proximal segments decelerate while distal segments accelerate. The aims of this study were to examine whether proximal segment deceleration is performed actively by antagonist muscles or is a passive consequence of distal segment movement, and whether distal segment acceleration is enhanced by proximal segment deceleration. Seventeen skilled taekwon-do practitioners were filmed using a high-speed camera while performing a high front kick. During kicking, EMG recordings were obtained from five major lower extremity muscles. Based on the kinematic data, inverse dynamics computations were performed yielding muscle moments and motiondependent moments. The results indicated that thigh deceleration was caused by motion-dependent moments arising from lower leg motion and not by active deceleration. This was supported by the EMG recordings. Lower leg acceleration was caused partly by a knee extensor muscle moment and partly by a motion-dependent moment arising from thigh angular velocity. Thus, lower leg acceleration was not enhanced by thigh deceleration. On the contrary, thigh deceleration, although not desirable, is unavoidable because of lower leg acceleration. [ABSTRACT FROM AUTHOR]

The cuticle strain which develops in the hindleg tibiae when a locust prepares to kick, or when the tibia thrusts against an obstacle, is detected by two campaniform sensilla, which reflexly excite the fast extensor tibiae motoneuron, some of the flexor tibiae motoneurons and nonspiking interneurons. The reflex excitation is adaptive for the extensor motoneuron during both co-activation and thrusting, but is only adaptive for the flexor motoneurons during co-activation, and is maladaptive during thrusting. We show that the femoral chordotonal organ, which monitors tibial position, controls the efficacy of the strain feedback. The campaniform sensilla-induced depolarization in the extensor motoneuron is about twice as large when the tendon is in mid position (reflecting a tibial-femoral angle of 90°) than when fully stretched (reflecting tibial flexion), while in the flexors the reverse is true. The amplitudes of excitatory postsynaptic potentials evoked by single campaniform sensilla spikes, are, however, not affected. Our data suggests that the chordotonal organ modulates the gain of the strain feedback onto the motoneurons by exciting interneuronal circuits whose output sums with the former. Thrusting typically occurs with the tibia partially extended, therefore the actions of the chordotonal organ support the production of a maximal thrusting force. [ABSTRACT FROM AUTHOR]

Locusts ( Schistocerca gregaria) use a distinctive motor pattern to extend the tibia of a hind leg rapidly in a kick. The necessary force is generated by an almost isometric contraction of the extensor tibiae muscle restrained by the co-contraction of the flexor tibiae (co-contraction phase) and aided by the mechanics of the femoro-tibial joint. The stored energy is delivered suddenly when the flexor muscle is inhibited. This paper analyses the activity of motor neurons to the major hind leg muscles during kicking, and relates it to tibial movements and the resultant forces. During the co-contraction phase flexor tibiae motor neurons are driven by apparently common sources of synaptic inputs to depolarized plateaus at which they spike. The two excitatory extensor motor neurons are also depolarized by similar patterns of synaptic inputs, but with the slow producing more spikes at higher frequencies than the fast. Trochanteral depressors spike at high frequency, the single levator tarsi at low frequency, and common inhibitors 2 and 3 spike sporadically. Trochanteral levators, depressor tarsi, and a retractor unguis motor neuron are hyperpolarized. Before the tibia extends all flexor motor neurons are hyperpolarized simultaneously, two common inhibitors, and the levator trochanter and depressor tarsi motor neurons are depolarized. Later, but still before the tibial movement starts, the extensor tibiae and levator tarsi motor neurons are hyperpolarized. After the movement has started, the extensor motor neurons are hyperpolarized further and the depressor trochanteris motor neurons are also hyperpolarized, indicating a contribution of both central and sensory feedback pathways. Variations in the duration of the co-contraction of almost twenty-fold, and in the number of spikes in the fast extensor tibiae motor neuron from 2-50 produce a spectrum of tibial extensions ranging from slow and weak, to rapid and powerful. Flexibility in the networks producing the motor pattern therefore results in a range of movements suited to the fluctuating requirements of the animal. [ABSTRACT FROM AUTHOR]

In a number of dairy farms, a restlessness of hind legs of cows during milking can be observed for no apparent reason. Previous studies have associated the hind leg activity of cows with mental or physical discomfort. Aim of this study was to investigate whether the observed hind leg activity was influenced by the milking process. The analysis was performed for total milking period and also separately for the following milking periods: let-down, main milk flow and over-milking. The following variables were analyzed for their influence on dairy cows' hind leg activity: the vacuum level in the MPC and SMT , the length of the milking periods, the vacuum curve type, bimodal curves and the presence of teat-end hyperkeratosis. In turn, it was also investigated whether the cows' hyperkeratosis is influenced by milking duration, length of milking periods or by the vacuum level in the SMT. Measurements and observations were done in ten milking parlors, each visited twice. Four milking units per parlor were equipped with vacuum loggers (VaDia 2.0, BioControl AS, Norway). One observer recorded hind leg activity per up to four cows, using the following categories: (1) stepping (claw raised < 15 cm) and (2) kicking (claw raised > 15 cm). A powerful, purposive kick to milking unit/milker was classified as p-kick (3) initially. Due to a small number of p-kicks, they were added to the number of kickings for further analysis. The analyses showed that none of the milking process-related variables had a significant influence on the dairy cows' prevalence to show hind leg activity. Although the prevalence was not influenced, the type of hind leg activity was. The hind leg activity kicking was observed at significantly higher average mouthpiece chamber vacuum levels than steppings. Cows showing kickings had a higher degree of teat-end hyperkeratosis than those showing steppings. The degree of teat-end hyperkeratosis was related to the milking duration. [ABSTRACT FROM AUTHOR]

INTRODUCTION: To score in soccer, players need to kick the ball with a high velocity, giving the goalkeeper less time to react. In a match, players often need to kick a moving ball and, to be more successful, need to be able to kick the ball with both feet proficiently. Although muscle activation during the kicking task has been studied [1,2], it is still unclear how limb dominance and ball condition affect lower limb muscles activation during an instep kick. METHODS: Ten experienced male soccer players (age: 21.9±1.9 yrs; BMI: 21.9±2.9 kg·m2; experience: 13.5±3.3 yrs) participated in the study. Eight surface EMG probes (FreeEMG300, BTS, Italy) were positioned on the muscle belly of the vastus medialis (VM), biceps femoris (BF), gastrocnemius medialis (GM) and tibialis anterior (TA) of both limbs. Subjects were asked to kick the ball inside a 1.5 X 1.5m target 3m away as fast as possible in four conditions: stationary ball and rolling ball with both the dominant and non-dominant feet (the ball rolled from behind the subjects at 2 m·-s1). Normalized peak activation was obtained for each kick. A repeated measures two-way ANOVA was used to identify differences between conditions and feet and partial eta-squared (ηp2) was used to measure effect size. RESULTS: There were no significant differences between positions or limbs. However, there were large partial eta-squared values for some comparisons: the swinging limb BF activation was higher when kicking with the dominant foot (ηp2 = 0.19) and when kicking a stationary ball (ηp2 = 0.25); the GM and the TA activation from the supporting limb were higher when kicking a moving ball (ηp2 = 0.35 and ηp2 = 0.18, respectively). CONCLUSIONS: Although we found no significant differences in this pilot study, the large effect sizes in some comparisons suggest that there could be a trend toward different muscle activations in these comparisons. The larger swinging BF activation in the stationary and dominant conditions suggest that there is greater co-contraction when performing these kicks; the larger support GM and TA activations when kicking a rolling ball suggest that muscles that act on the ankle joint could be more active to stabilize the joint during this task. Future studies with a greater sample size can clarify how lower limb muscle activation function in different kicking conditions and possibly help to direct training and consequently improve player's performance. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Besides being accurate, successful kicks in soccer usually generate the highest ball velocity possible (often measured in laboratory as the foot velocity), giving the goalkeeper less time to react (1, 2). Also, a high level of intersegmental coordination is required to perform an effective kick (3). The swinging limb must coordinate to achieve maximal foot velocity at the moment of ball impact, while the support limb must position the body's center of mass in an optimal position. Although intersegmental coordination is fundamental for a successful kick, it is still unclear if there are direct associations between joint angles and foot velocity at the moment of impact. Therefore, we evaluated the associations between joint angles and foot velocity during different maximal instep kicks. METHODS: 18 male soccer players (age: 21±2 yrs, BMI: 22.4±1.9 kg·m-2, exp: 14±2 yrs) participated in the study. Players performed three kicks with the ball stationary or rolling (~2 m·s-1) from four different directions (anterior, posterior, medial, or lateral) and with both feet. They approached the ball at a 45° angle and kicked it as fast as possible with the instep portion of the foot, hitting a target (1.2x1.2m) positioned 3m away. Swinging foot velocity, the distance between support and swinging feet, and angles in the sagittal plane for the hip, knee, and ankle joints at the moment of ball impact were measured with 3D motion capture (BTS, Italy). Correlations between kick performance (foot velocity) and joint angles and feet distance were assessed with Pearson's correlation (a<0.05). RESULTS: Foot velocity was significantly correlated with all variables, except swinging knee flexion angle (p=0.118; r=-0.117). Higher foot velocities were correlated with increased swinging ankle plantarflexion (p<0.001; r=-0.436), swinging hip extension (p=0.003; r=-0.217), support hip (p=0.008; r=-0.198) and knee (p<0.001; r=-0.331) extension, support ankle plantarflexion (p<0.001; r=-0.288) and feet distance (p=0.001; r=0.241). CONCLUSION: Foot speed velocity was associated with joint angles in both limbs, with the highest correlations associated with increased swinging ankle plantarflexion and support knee flexion. Furthermore, the distance between the support and swinging feet at the moment of ball impact also seems to be relevant factor. Coaches and athletes should consider the hip, knee and ankle angles of both limbs and the distance between feet to improve kicking performance. [ABSTRACT FROM AUTHOR]

Hamstring muscle strain injury is one of the most common injuries in sports involving sprinting and kicking. Studies examining hamstring kinematics and activations are rich for sprinting but lacking for kicking. The purpose of this study was to examine kinematics and activations of hamstring muscles in instep and cut-off kicking tasks frequently performed in soccer. Videographic and electromyographic (EMG) data were collected for 11 male soccer-majored college students performing the two kicking tasks. Peak hamstring muscle-tendon unit lengths, elongation velocities, and maximum linear envelop EMG data were identified and compared among hamstring muscles and between kicking tasks. Hamstring muscles exhibited activated elongations before and after the contact of the kicking foot with the ball. The muscle-tendon unit lengths peaked in the follow-through phase. The peak elongation velocity of the semimembranosus was significantly greater than that of the semitendinosus and biceps femoris (p = 0.001). The maximum linear envelop EMG of the biceps femoris was significantly greater than that of the semimembranosus (p = 0.026). The potential for hamstring injury exists in the follow-through phase of each kicking task. The increased hamstring muscle-tendon unit elongation velocities in kicking tasks may explain the more severe hamstring injuries in kicking compared to sprinting. [ABSTRACT FROM AUTHOR]

As the focus on the elite Australian Football League competition becomes greater so too does the demand for success. Clubs are heavily scrutinized for their draft selections and as such are taking more interest in the younger levels of competition in an attempt to identify and monitor talent. Based on contemporary talent identification knowledge, this review examines the current talent identification process in Australian football, with a focus on areas to potentially improve or inform future developments. Currently, a significant gap exists between static and isolated assessment procedures used to identify talent in Australian football and the dynamic nature of match play. Future assessments should consider factors such as maturation, fatigue and ecological dynamics. The addition of a valid and reliable technical skill assessment (e.g., a small-sided game) to the current Australian Football League draft combine was recommended., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Bonney, Larkin and Ball.)