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Motivation: The precise identification of punches and kicks in martial arts sporting competitions is a critical issue, often complex, and at times subject to controversies due to the subjective judgment of referees. Problem: The subjectivity in assessing punches and kicks during martial arts sporting competitions poses a significant challenge regarding impartiality and accuracy in refereeing. Solution Approach: This study analyzes the most recent contributions to punch and kick recognition in martial arts competitions. It reviews classification techniques, commonly used sensors, and the performance achieved in identifying these movements. Results: The analysis provides a general overview of implemented punch and kick classification techniques. This contributes to understanding recent advancements in this field and how they can enhance objectivity and precision in refereeing martial arts competitions. Conclusions: This study underscores the growing interest in machine learning techniques for classifying punches and kicks in martial arts, encompassing a wide range of classifiers, from traditional methods to deep learning models. The combination of inertial sensors and depth cameras emerges as a promising avenue. Future research is expected to thoroughly compare and characterize these approaches, paving the way for implementing artificial intelligence systems in martial arts competitions and potentially revolutionizing the objectivity in assessing movements in this sport. [ABSTRACT FROM AUTHOR]

Introduction: Optimising post-strike ball velocity is essential for success in football. Biomechanical factors play a significant role in determining ball speed. However, further investigation is needed to understand the specific relationships between the biomechanical factors and post-strike ball velocity in football players. Aim: To identify the key biomechanical factors contributing to post-strike ball velocity and provide insights for enhancing performance in league-level football players. Materials and Methods: A cross-sectional study was conducted in the Department of Arthroscopy and Sports Medicine at the Sri Ramachandra Centre for Sports Science, Tamil Nadu, India. The duration of the study was five months, from January 2022 to May 2022. The study included 25 professional male football players from national-level league teams. Participants performed maximal instep kicks while various kinematic variables were measured using Vicon cameras, Advanced Mechanical Technology Inc., (AMTI) force footplates, and a radar speed gun. Data processing was performed using Vicon Nexus software version 2.7. The data were analysed using R statistical software version 4.0.2. The Analysis of Variance (ANOVA), followed by Tukey's Honestly Significant Difference (HSD) post-hoc tests, were used to compare the various kick matrices across the players. Pearson's r correlation analysis was used to check for a correlation between post-strike ball velocity and other kick matrices. Multiple regression analysis was conducted to examine the relative effects of various kick matrices on post-strike ball velocity, with significance set at a p-value <0.05. Results: The mean age of the study participants was 18.8 years. A significant positive correlation was observed between prestrike foot velocity (r=0.58) and training experience (r=0.48) with post-strike ball velocity. Step-wise multiple linear regression analysis revealed that 39% of the variance in post-strike ball velocity could be attributed to training experience and prestrike foot velocity. Conclusion: Training experience and prestrike foot velocity could be the most important factors to consider in order to maximise post-strike ball velocity among league-level football players. [ABSTRACT FROM AUTHOR]

Background: People with Parkinson's disease (PD) benefit from boxing exercise. Adding kicking variations to the boxing may provide additional benefit to improve balance. However, the benefits and adherence to such trainings is unknown. Objective: To explore the feasibility, safety, and benefits on balance of boxing training combined with kicking techniques in comparison to boxing without kicking in PD. Methods: Participants were randomized to group-based boxing training with kicking techniques (BK) or to group-based boxing alone training (BO). Both groups trained for one hour, once a week, for a period of 10 weeks. Participants were assessed at baseline and ten weeks post-intervention for difference in balance, fear of falling, balance confidence, walking ability, and quality of life. Results: Twenty-nine people with PD (median age 64 years; median disease duration 5 years) participated. Both interventions were feasible and acceptable for all participants. No adverse events occurred. Most participants (BK 80%; BO 75%) were satisfied with the training. We found no significant between group difference on either the primary (Mini-BEST) or secondary outcomes. The within group comparison showed that balance improved in both groups after the intervention (BK 22.60 (2.7) to 25.33 (2.64) p = 0.02; BO 23.09 (3.44) to 25.80 (2.39); p = 0.01 on the Mini BEST test). Conclusion: Both types of boxing seem to be feasible and safe. Adding kicking techniques to boxing does not improve balance significantly more than boxing alone. Incorporation of kicking may be a valuable addition to the exercise therapy repertoire. [ABSTRACT FROM AUTHOR]

Purpose: Studies on object control skills (OCS) have described changes in movement patterns over time, but mostly in children and adolescents, young adults, or older adults. Most of these studies focused on only one skill and usually only on the process- or product-oriented outcomes. Thus, this study aimed to explore OCS performance in children, younger adults, and older adults. Methods: A total of 120 male participants took part in this study, including 78 primary school children (7.96 ± 1.22 years), 22 young adults (23.5 ± 2.34 years), and 20 older adults (69.5 ± 4.43 years). We assessed the process-oriented performance of throwing, kicking, and catching performance using the component approach. Throwing and kicking velocity was recorded with a STALKER SOLO 2.0 radar gun. For catching, the number of caught balls was assessed. Results. Young adults had the highest component levels in all OCS; they also produced significantly higher throwing and kicking velocities than children and older adults. The proportion of participants achieving mastery or advanced skill proficiency varied significantly in children (6.4–32.1%), young adults (63.6–100.0%), and older adults (10.0–95.0%). With few exceptions, the results showed mainly moderately significant correlations between developmental levels and throwing/kicking velocity or number of successfully caught balls for all age groups. Conclusion: Our data indicate that children in particular rarely demonstrate advanced OCS and that there is a decrease in throwing and kicking but not in catching in older adults compared to the younger age groups. [ABSTRACT FROM AUTHOR]

Improved pass accuracy is a prominent determinant of success in football. It demands an effective interaction of complex behavioral and cortical dynamics. Exploring differences in the ability to sustain an accurate pass behavior in a stable setting and the associated cortical dynamics at different expertise levels may provide an insight into skilled strategies contributing to superior accuracy in football. The aim of this study is to compare trial-to-trial variability of pass biomechanics and the corresponding cortical dynamics during short-distance passes between novices and experienced football players. Thirty participants (15 novices, 15 football players) performed 90 short-distance passes. The intertrial variability of pass biomechanics (foot acceleration, range of hip flexion, knee flexion and foot rotation) was assessed by means of multiscale entropy. The task-related cortical dynamics were analyzed via source-derived event-related spectral perturbations. Experienced players demonstrated higher accuracy and overall lower entropy values across multiple time scales which was significant for hip flexion. The electroencephalography data revealed group differences in parieto-occipital alpha desynchronization and frontal theta synchronization in successive phases of passes. The current findings suggest that experienced football players may show a skilled ability to recruit and retain pass biomechanics promoting higher accuracy, whereas novices may show an explorative behavior with higher spatial variability. This difference may be associated with distinctive visuospatial and attentional strategies acquired with expertise in football. Our study provides an insight into expertise-specific behavioral and cortical dynamics of superior accuracy in football and a basis for its prospective investigation in enriched contexts. [ABSTRACT FROM AUTHOR]

Past investigations provided limited information regarding instep kicking kinematics in soccer. It is unclear how foot dominance and ball approach angle impact whole-body kinematics and consequently the ball velocity. We aimed to analyse the effects of the ball approach angle and the foot used on the whole-body kinematics of soccer players performing an instep kick. Twenty-four soccer players performed maximal instep kicks, using the dominant and non-dominant feet, with the ball stationary or rolling from four different directions. Whole-body motion was recorded during the kicking action and kinematic time-series were extracted and resampled to 200 points equally divided into kicking and follow-through phases. 1-D statistical parametric mapping two-way ANOVA tested for the effect of ball condition and foot dominance. Ball approach angle affected most of the swinging and support limb variables and some upper body variables. Performance-related variables such as CoM, foot, and shank velocities were reduced when the ball approached posteriorly. The linear and angular velocities of the swinging limb, and CoM vertical position, were higher when kicking with dominant foot. Based on these findings, as a practical implication, coaches should vary ball approach angles and the foot used during kicking drills to improve technical effectiveness in various situations. [ABSTRACT FROM AUTHOR]

Kicking is fundamental in many field-based sports. Most studies investigating kicking performance have been conducted with male athletes, resulting in a dearth of specific data to inform coaching of this skill in female players. This systematic review aimed to compare kicking biomechanics in male and female athletes in field-based sports. As per PRISMA guidelines, articles were retrieved from searches across five online databases. Studies investigating kicking biomechanics in field-based athletes of both sexes were eligible for inclusion. Articles were screened using Covidence and data extracted based on STROBE recommendations. The review included 23 studies, featuring 455 soccer players. Male athletes produced significantly greater ball velocities and linear velocities of the ankle, foot, and toe than females. Males had greater ankle plantarflexion angles than females at ball strike, while females used larger trunk flexion ranges than males. Hip and knee torques and ball-to-foot velocity ratios were greater in men than women. Skilled players generated power using tension arcs; a technique not seen in novices. Skill level within sex may have a greater influence on kicking performance than differences between the sexes. This review highlights the need for further research investigating kicking performance in both sexes across the spectrum of sports. [ABSTRACT FROM AUTHOR]

The study features a biomechanical analysis of kicking the ball in rugby. Although rugby has a long history, it is understudied in our country. When taking a place kick in the game, the ball should achieve its maximum speed. The skills of place kicking are unique because of the specific shape of the ball, the use of kicking tee, and the angles of the swing. Here we shall explore this proximal-distal sequence aka the combined speed principle with the outcome of reaching maximum ball speed, which requires maximum speed of the foot prior to the contact with the ball. [ABSTRACT FROM AUTHOR]

In Australian Football (AF), small-sided games (SSGs) are used extensively to replicate particular technical, tactical or physiological responses. Whilst research on SSGs has been extensive in soccer, in AF it has been limited to agility demands and exploring the effect of field dimensions on technical skill (i.e., handballing) and physical responses of senior athletes. Therefore, this study investigated the effect of four different SSG player number conditions (5v5, 5v6, 6v6, 7v7) on the technical (e.g., kicking) and physical (i.e., odometer, m-min−1, max velocity and percentage of high intensity running) performance outcomes in 22 sub-elite youth AF players. Particular constraints were applied to the SSG to ensure the focus was on kicking (i.e., after each handball a kick must be performed). The results of this study demonstrate when more technical events are required under more pressured situations (i.e., physical and time) the 5v6 condition appears to be most appropriate. However, when the focus is on kicking to a contested possession (i.e., kicking to leading or covered players) balanced player numbers (e.g., 6v6) would appear optimal. Alternatively, when the SSG focus is on increasing physiological demands (i.e., m.min−1) lower player density conditions (i.e., 5v5) appear more suitable. [ABSTRACT FROM AUTHOR]

Football boots are marketed with a specific performance feature focus, for example, power boots are marketed for optimal shooting performance. However, little evidence exists on the impact of boot design on shooting performance. This study assessed the effect of upper padding on shooting velocity and accuracy using a test–retest reliable test setup. Nine university level football players performed a protocol of shooting to: (1) maximise velocity; and (2) maximise accuracy in football boots with and without upper padding (Poron Memory foam). The protocol was completed twice; the non-padded boot results were used for test–retest validation, while the non-padded versus padding results were used to investigate the effect of padding. Velocity was assessed through actual ball velocity, percentage of maximum velocity and perceived velocity. Accuracy was assessed through radial offset, vertical offset, horizontal offset, success (goal/no goal), zonal offset and perceived accuracy. No significant differences between boots were observed in the velocity measures for either velocity or accuracy focused shots. Significant differences between boots were observed in vertical offset for both accuracy (without padding mean ± standard deviation − 0.02 ± 1.05 m, with padding 0.28 ± 0.87 m, P = 0.029) and velocity (without padding 0.04 ± 1.33 m, with padding 0.38 ± 0.86 m, P = 0.042) focused shots resulting in more missed shots above the goal for the padded boot (without padding 41–43% missed, with padding 56–72% missed). These findings suggest the addition of upper padding has a negative impact on shooting accuracy while not impacting shooting velocity. [ABSTRACT FROM AUTHOR]

Purpose: In Australian Football (AF), the ability to proficiently kick the ball is a critical skill and has been shown to be advantageous to a team's successful performance; however, a valid and reliable match referenced kicking assessment remains absent. Therefore, the aim of this study was to develop a valid and reliable AF kicking proficiency assessment comparative to match play kicking performance. Method: Youth male Australian Football players (n = 251) from different stages within the AF talent pathway were recruited. The developed AFFB-DKA (Australian Football Field-Based-Dynamic Kicking Assessment) considered particular constraints of match play kicking demands such as kick type, distance, delivery, and locomotion of the player receiving the ball. In total, 14 kicks were completed during the test. Validity (i.e., content, logical and construct) and reliability (i.e., test re-test) were assessed. Results: Findings indicate the kicking test can distinguish across and between age (i.e., U14; U16; U18) and skill groups (i.e., club; sub-elite; elite). The timeframe between U14 and U16 was identified as a potential key period where kicking skill acquisition may be most impressionable; however, further research is recommended to support this. Conclusion: The developed AFFB-DKA is the first Australian Football specific kicking assessment to consider and apply match play kicking constraints to make a more representative, valid and reliable assessment. [ABSTRACT FROM AUTHOR]

In Australian Football (AF), small sided games have been used extensively as an alternative training method for technical and physical adaptations. Considering their application to AF, it is surprising a valid and reliable small-sided game kicking assessment remains absent. Therefore, the aim of this study was to develop a valid and reliable 5v6 Australian football small-sided game kicking proficiency assessment. Youth male AF players (n = 145) from different stages within the AF talent pathway were recruited. Validity (i.e., logical and construct) and reliability (i.e., test re-test) were assessed. The largest kicking proficiency difference was between U13 and U16 players and between novice and sub-elite players. Between the ages of U16 and U18 kicking proficiency appears to stabilise. The Australian football small-sided kicking assessment was 97% successful in identifying players as either novice or sub-elite. Larger physical performance (i.e., odometer, m/min−1 and %HIR) outputs were noted between U14 and U18 players and novice and sub-elite players. Collectively, these findings suggest the Australian football small-sided kicking assessment is a valid and reliable AF kicking proficiency assessment tool and may provide worthwhile information to coaches regarding kicking performance along the AFL pathway, to profile player strengths whilst identifying specific areas of improvement. [ABSTRACT FROM AUTHOR]

The appropriate determination of performance outcome is critical when appraising a performer's technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions. [ABSTRACT FROM AUTHOR]

• Machine learning algorithms can be used to inform practice design in team sports. • Modelling match constraint interactions facilitates objective player assessment. • The interaction of match constraints varies under different competition settings. Representative learning design is a key feature of the theory of ecological dynamics, conceptualising how task constraints can be manipulated in training designs to help athletes self-regulate during their interactions with information-rich performance environments. Implementation of analytical methodologies can support representative designs of practice environments by practitioners recording how interacting constraints influence events, that emerge under performance conditions. To determine key task constraints on kicking skill performance, the extent to which interactions of constraints differ in prevalence and influence on kicking skills was investigated across competition tiers in Australian Football (AF). A data sample of kicks (n = 29,153) was collected during junior, state-level and national league matches. Key task constraints were recorded for each kick, with performance outcome recorded as effective or ineffective. Rules were based on frequency and strength of associations between constraints and kick outcomes, generated using the Apriori algorithm. Univariate analysis revealed that low kicking effectiveness was associated with physical pressure (37%), whereas high efficiency emerged when kicking to an open target (70%). Between-competition comparisons showed differences in constraint interactions through seven unique rules and differences in confidence levels in shared rules. Results showed how understanding of key constraints interactions, and prevalence during competitive performance, can be used to inform representative learning designs in athlete training programmes. Findings can be used to specify how the competitive performance environment differs between competition tiers, supporting the specification of information in training designs, representative of different performance levels. [ABSTRACT FROM AUTHOR]

To assess ball impact force during soccer kicking is important to quantify from both performance and chronic injury prevention perspectives. We aimed to verify the appropriateness of previous models used to estimate ball impact force and to propose an improved model to better capture the time history of ball impact force. A soccer ball was fired directly onto a force platform (10 kHz) at five realistic kicking ball velocities and ball behaviour was captured by a high-speed camera (5,000 Hz). The time history of ball impact force was estimated using three existing models and two new models. A new mathematical model that took into account a rapid change in ball surface area and heterogeneous ball deformation showed a distinctive advantage to estimate the peak forces and its occurrence times and to reproduce time history of ball impact forces more precisely, thereby reinforcing the possible mechanics of ‘footballer’s ankle’. Ball impact time was also systematically shortened when ball velocity increases in contrast to practical understanding for producing faster ball velocity, however, the aspect of ball contact time must be considered carefully from practical point of view. [ABSTRACT FROM AUTHOR]

Background: Amputee football is a worldwide popular sport with positive physical and psychological effects on the disabled. Amputee players use their hands dominantly for locomotion. However, the effect of using upper extremity which is not accommodated to loading is not very well known.Research Question: The objective of this study was to determine the load distribution of amputee football players during walking, running and kicking the ball.Methods: This study was conducted with 15 certified amputee football players (age 24.5 ± 5.8 years, body weight 62.3 ± 10.9 kg, height 171.6 ± 7.7 cm). The loads on their non-amputated lower extremity were measured with F-Scan mobile system sensors inserted in their shoes, and the loads on their upper extremities were measured with F-Grip system sensors affixed to the gloves. The participants were asked to walk, run and kick the ball using Lofstrand Crutches.Results: The maximum loading on the upper extremities during walking, running and kicking the ball varied between 111% and 175% of the body weight. While loading during walking and running was similar, the loading on the upper extremity during kicking the ball exceeded that of walking by 58.1% and running by 47.4%. The maximum loading on the non-amputated lower extremity varied between 134% and 196% of the body weight. Loading during running was 46.2% higher than that of walking. The loading on the foot during kicking the ball was 45.7% higher than that of walking. The loading on the foot during running and kicking were similar.Significance: Walking-running-kicking the ball with LC resulted in unusual loading particularly on the upper extremity. During running, the increased loading was transferred to the foot rather than the hands. During kicking, the loading increased extremely and was mainly transferred to the hands. The frequent repetition of kicking during the game may therefore increase the incidence of upper extremity injuries. [ABSTRACT FROM AUTHOR]

A mechanical field-goal kicking machine was used to investigate toppling ball flight in American football place-kicking, eliminating a number of uncontrollable impact variables present with a human kicker. Ball flight trajectories were recorded using a triangulation-based projectile tracking system to account for the football’s 3-dimensional position during flight as well as initial launch conditions. The football flights were described using kinematic equations relating to projectile motion including stagnant air drag and were compared to measured trajectories as well as projectile motion equations that exclude stagnant air drag. Measured football flight range deviations from the non-drag equations of projectile motion corresponded to deficits between 9 and 31%, which is described by a football toppling compound drag coefficient of 0.007 ± 0.003 kg/m. Independent variables including impact location and impact angle orientation resulted in 15 impact conditions. We found that an impact location of 5.5 cm from the bottom of the ball maximized trajectory height and distance. At the 5.5-cm impact location, alterations in impact angle produced minimal change in football trajectory, including launch angle (range = 1.96 deg), launch speed (range = 1.06 m/s), and range (range = 0.94 m). [ABSTRACT FROM AUTHOR]

Wearable inertial measurement systems (IMS) allow for three-dimensional analysis of human movements in a sport-specific setting. This study examined the concurrent validity of a IMS (Xsens MVN system) for measuring lower extremity and pelvis kinematics in comparison to a Vicon motion analysis system (MAS) during kicking. Thirty footballers from Australian football (n = 10), soccer (n = 10), rugby league and rugby union (n = 10) clubs completed 20 kicks across four conditions. Concurrent validity was assessed using a linear mixed-modelling approach, which allowed the partition of between and within-subject variance from the device measurement error. Results were expressed in raw and standardised units for assessments of differences in means and measurement error, and interpreted via non-clinical magnitude-based inferences. Trivial to small differences were found in linear velocities (foot and pelvis), angular velocities (knee, shank and thigh), sagittal joint (knee and hip) and segment angle (shank and pelvis) means (mean difference: 0.2–5.8%) between the IMS and MAS in Australian football, soccer and the rugby codes. Trivial to small measurement errors (from 0.1 to 5.8%) were found between the IMS and MAS in all kinematic parameters. The IMS demonstrated acceptable levels of concurrent validity compared to a MAS when measuring kicking biomechanics across the four football codes. Wearable IMS offers various benefits over MAS, such as, out-of-laboratory testing, larger measurement range and quick data output, to help improve the ecological validity of biomechanical testing and the timing of feedback. The results advocate the use of IMS to quantify biomechanics of high-velocity movements in sport-specific settings. [ABSTRACT FROM AUTHOR]

An accurate measurement of force and biomechanical energy that people can impart through kicking is useful for kick-related sports training. Existing methods are indirect measurements or focus on force and not on the total energy of the kick. A kick test rig was designed, constructed and instrumented to measure the force and displacement of a vertical target subjected to kicking. The kick energy was calculated from the recorded force and displacement histories. The methodology for measurement of kick force and energy was validated by an open stance front kick test by 52 volunteers. The results showed that 67% of the participants could achieve an average energy above 100 J. An increasing trend of kick energy with increasing body weight of participant was observed. The participant’s gender had a strong influence on the kick energy, while training in martial arts does not appear to be a significant parameter. A probability analysis showed that one in one hundred adults will be able to kick with energies exceeding 215 J. [ABSTRACT FROM AUTHOR]

Foam nests have evolved independently in several amphibian groups as an adaptive response to prevent predation and desiccation in dry environments. Nests are normally laid on ponds, or in underground galleries, humid forest leaf litter or terrestrial bromeliads. They are built when males or females beat a foam precursor associated with the egg masses extruded by the female. The spawning process requires the synchronic actions of the mating pair to obtain a hemispheric nest that protects the offspring. Herein, we describe the spawning behaviour ofEngystomopspustulatusbased on videos from 13 nesting couples from the lowlands of western Ecuador. Three variables were measured as indicators of male effort: duration of mixing events, duration of resting periods, and number of kicks per mixing event. We consider that not only male physical effort but also female behaviour influences nest structure. We suggest that nest building requires prolonged and intense physical activity by the male as well as the female’s steady position during spawning and female’s oviposition site selection. Nest building has two phases. In the first phase, the duration of resting periods, the duration of mixing events, and the number of kicks increase and are highly variable. During the second phase the three variables stabilise until the end. The volume of the nest increased mainly during the second phase. In four nesting events we observed kicking movements by the female. To our knowledge, this is the first time that female kicking has been observed in leptodactylid frogs. The function of this behaviour is unknown but our observations suggest that it may be triggered by insufficient male effort. Traditionally, female mate choice inEngystomopshas been explained under models of indirect benefits exclusively. We argue that the prolonged male activity during nesting could influence female fitness directly. This will allow the operation of sexual selection via direct benefits. [ABSTRACT FROM PUBLISHER]

Locusts jump by using a catapult mechanism in which energy produced by slow contractions of the extensor tibiae muscles of the hind legs is stored in distortions of the exoskeleton, most notably (1) the two semi-lunar processes at each knee joint and (2) the tendons of the extensor muscles themselves. The energy is then suddenly released from these stores to power the rapid, propulsive movements of the hind legs. The reliance on the mechanical storage of energy is likely to impact on jumping because growth occurs by a series of five moults, at each of which the exoskeleton is replaced by a new one. All developmental stages (instars) nevertheless jump as a means of forward locomotion, or as an escape movement. Here, I show that in each instar, resilin is added to the semi-lunar processes and to the core of the extensor tendons so that their thickness increases. As the next moult approaches, a new exoskeleton forms within the old one, with resilin already present in the new semi-lunar processes. The old exoskeleton, the tendons and their resilin are discarded at moulting. The resilin of the semi-lunar processes and tendons of the new instar is initially thin, but a similar pattern of deposition results in an increase of their thickness. In adults, resilin continues to be deposited so that at 4 weeks old the thickness in the semi-lunar processes has increased fourfold. These changes in the energy stores accompany changes in jumping ability and performance during each moulting cycle. [ABSTRACT FROM AUTHOR]

Soccer kicking training should be adjusted to the characteristics of the athletes. Therefore, examination of differences in kicking kinematics of females and pubertal players relative to males is worthwhile. The purpose of the study was to compare kicking kinematics and segmental sequence parameters between male, female, and pubertal players. Ten adult male, ten adult female, and ten male pubertal players participated in the study. Participants performed five consecutive kicking trials of a stationary ball, as powerful as they could. Analysis of variance showed significantly higher ball velocity, higher joint linear velocities for the knee and the hip, and higher angular velocities of the knee and the ankle for males compared to female and pubertal players (p < 0.05). Similarly, the peak joint velocity was achieved significantly closer to ball impact in males compared to other groups (p < 0.05). Males also showed a more plantarflexed ankle immediately before ball impact (p < 0.05). Females and pubertal players may benefit from skill training aiming to increase ankle plantarflexion and hip flexion prior to ball impact, and to adjust thigh and shank motion, such that the shank–foot segment travels through a higher range of motion and with a greater velocity. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate the relationships between repeated explosive effort sequences (20 + 20 m shuttle sprint with change of direction, kicking and jumping), metabolic response (lactate and ammonia), and fitness qualities (strength and endurance) in under-19 soccer players. 21 players completed: 1) sprint test: 30 m (T30 ) and 40 m (20 + 20 m) shuttle sprints; 2) countermovement jumps (CMJ); 3) maximal kicking; and 4) 9 repeated-explosive effort sequences (RES); 4) a progressive isoinertial loading test in full squat to determine the load which subjects achieved ~1 m · s −1 (V1 - load); 6) Yo-Yo Intermittent Recovery Test Level 1 (YYIRT-1). Mean sprint time of the 9 repeated sprints (RSAmean1–9 ) showed correlation with V 1 - load (r = − 0.52 [− 0.79, − 0.25]) metabolic response (lactate, r = 0.67 [0.47, 0.87] and ammonia, r = 0.53 [0.27, 0.79]). YYIRT-1 correlated with RSAmean1-9. (rw = − 0.78 [− 0.92, − 0.64]) when the body weight was controlled. Furthermore, the 3 first sprints (RSAmean1-3 ) correlated with RSAbest (r = 0.93 [0.88, 0.98]), V 1 -load (r = − 0.64 [ − 0.86, − 0.42]), and T30 (r = 0.63 [0.41, 0.85]). These results suggest that the soccer player’s lower body strength (V1 -load, jumping and sprinting) explains a large part of the performance in the first sequences, whereas the aerobic capacity, estimated through YYIRT-1, becomes more important to performance as the number of sprints is increases. [ABSTRACT FROM AUTHOR]

The current investigation aimed to determine whether there are differences in ball velocity and 3D kinematics when performing maximal kicks with the dominant and non-dominant limbs. Seventeen male academy soccer players performed maximal speed place kicks with their dominant and the non-dominant limbs. The 3D kinematics of the lower extremities were obtained using a 10-camera motion capture system operating at 500 Hz. Hip, knee and ankle joint kinematics were quantified in the sagittal, coronal and transverse planes and then contrasted using pairedt-tests. Significantly higher ball velocities were obtained with the dominant limb. Foot linear velocity and knee extension velocity at ball contact were also found to be significantly greater in the dominant limb. That reduced ball velocities were observed between kicking limbs highlights the potential performance detriments that may occur when kicking with the non-dominant limb; thus, it is recommended that additional bilateral training be undertaken in order to attenuate this and improve overall kicking performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] The NIRK is performed relying on the movement of all lower limb segments. [•] The final part of the NIRK presents a more in-phase action of hip and knee. [•] A reduced angular momentum was observed in the final part of the NIRK. [•] The NIRK presents a reduced angular momentum about the vertical axis. [Copyright &y& Elsevier]

The aim of this study was to investigate the effects of target distance on temporal and impact force parameters that are important performance factors in taekwondo kicks. Forty-nine taekwondo athletes (age = 24.5 ± 5.9 years; mass = 79.9 ± 10.8 kg) were recruited: 13 male experts, 21 male novices, 8 female experts, and 6 female novices. Impact force, reaction time, and execution time were computed. Three-way repeated measure ANOVAs revealed significant ‘distance’ effect on impact force, reaction time, and execution time (p = 0.001). Comparisons between distance conditions revealed that taekwondo athletes kicked with higher impact force from short distance (17.6 ± 7.5 N/kg) than from long distance (13.1 ± 5.7 N/kg) (p < 0.001), had lower reaction time from short distance (498 ± 90 ms) and normal distance (521 ± 111 ms) than from long distance (602 ± 121 ms) (p < 0.001), and had lower execution time from short distance (261 ± 69 ms/m) than from normal distance (306 ± 105 ms/m) or from long distance (350 ± 106 ms/m) (p = 0.003 andp < 0.001, respectively). In conclusion, target distance affected the kick performance; as distance increases, impact force decreased and reaction time increased. Therefore, when reaction to a simple visual stimulus is needed, kicking from a long distance is not recommended, as longer time is required to respond. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

Abstract: Balance control is presumed to be a fundamental constraint on the organization of skilled movement. The current experiment explored whether single-leg balance ability predicted kicking performance on the other leg. Thirty-eight participants ranging widely in skill kicked a soccer ball with the right and left legs for maximum accuracy and velocity and performed single-leg balance on a force plate for 30s with the right and left legs. Significant correlations between single-leg balance and kicking accuracy, but not velocity, were found. Left leg balance was more highly correlated than right leg balance with right (dominant) leg kicking accuracy. However, the same pattern of relations was not seen between single-leg balance and left (non-dominant) leg kicking accuracy. These findings provide preliminary support for the importance of balance ability in kicking performance. The importance of balance in the production of athletic skills is discussed and additional experimental paradigms are suggested that might further our knowledge in this area. [Copyright &y& Elsevier]

Cutting in soccer is a common skill used to avoid the opponent's pressure but the potential effects of such a skill on instep kicking performance have not been previously investigated. The purpose of this study was to examine the differences in lower limb biomechanics between straight approach soccer kicks and kicks performed following a cutting maneuver task. Ten young amateur soccer players performed, in a random order, instep kicks after a two-step straight approach run and kicks after a double 'faking' cutting maneuver task. The results showed that kicking after a cutting maneuver task displayed significantly lower ball speed values compared with the straight approach instep kicking (16.73 vs. 19.78 m/s, respectively; p < 0.05). Moreover, analysis of variance showed significant differences between the two kicking conditions in ankle, knee and hip joint displacements. The present study indicated that performing instep kicks after a double-cutting maneuver reduces ball and foot speed probably due to increasing joint frontal and transverse plane rotations. Improvements in the performance of the cutting maneuver task through training might result in better transfer of energy and speed to the kicking task thus permitting players to perform more powerful kicks under realistic game conditions. [ABSTRACT FROM AUTHOR]

The kicking skill of the individual player is of great importance in soccer, and two parameters can be identified as being important in soccer kicking - achieving high speed of the ball and accuracy of performance. The purpose of the current study was to examine the influence of different speeds of approach on the maximal speed of the ball when kicking a stationary ball, and to examine the influence of accuracy of performance on the maximal speed of the ball relevant to a penalty kick. Seven male soccer players kicked for maximal speed of the ball (I) with a self-selected angle and speed of approach, (II) with accuracy demand placed on the subjects, (III) with a straight-line approach of different velocities ranging from 0 m/s to maximal running speed. The maximal speed of the ball was between 28.60 and 34.48 m/s. An accuracy constraint caused the speed of the ball to decline to 85%. With a straight-line approach, the maximal speed of the ball was between 25.64 and 32.26 m/s. When the subjects approached the ball at speeds other than the self-selected speed of approach, the speed of the ball declined, indicating a subject-specific optimal speed of approach. [ABSTRACT FROM AUTHOR]

The article discusses the study which determines the effect of stroke rate (SR) and stroke length (SL) manipulation on oxygen uptake (VO2) response during swimming at a constant speed. It states that the study was participated by six males and four females, who are middle-distance freestyle swimmers and are engaged in masters or collegiate swimming program. It also mentions that participants, who wore aquatic metronome to manipulate SR, performed the swimming trials in Unidyne flume at Minneapolis, Minnesota with a speed of 1.0 m⋅s-¹. It relates that VO2 was assessed using Douglas bag technique, breath-by-breath measurement through online system and heart rate with a Tissot spirometer. Result shows that there is increase in VO2 by 11.4% and HR by 4.0% when SR was increased to 10%.

Kicking is the defining action of soccer, so it is appropriate to review the scientific work that provides a basis of our understanding of this skill. The focus of this review is biomechanical in nature and builds on and extends previous reviews and overviews. While much is known about the biomechanics of the kicking leg, there are several other aspects of the kick that have been the subject of recent exploration. Researchers have widened their interest to consider the kick beginning from the way a player approaches the ball to the end of ball flight, the point that determines the success of the kick. This interest has encapsulated characteristics of overall technique and the influences of the upper body, support leg and pelvis on the kicking action, foot-ball impact and the influences of footwear and soccer balls, ball launch characteristics and corresponding flight of the ball. This review evaluates these and attempts to provide direction for future research. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]