Instep Kick Research Articles

Inter-individual variability in elliptical and diagonal error distributions potentially relevant to optimal motor planning in football instep kicking

The distribution of motor errors can influence optimal motor planning (where to aim). In football instep kicking, it was shown that ball landing locations exhibit the right-up-left-down elliptical distribution in right-footed kickers and vice versa. However, this was reported as a result of mixed multiple kickers; the individual-level error distribution has been unclear. Here we show substantial inter-individual variability in error shape and error direction in the 30 kicks aimed at a target (1.7 m high, 11.0 m in front) by 27 male football players. All players exhibit right-up-left-down distributions with ellipticity (minor/major radius ratio of the 95% confidence ellipse) ranging from 0.25 to 0.77 and major axis angle ranging from 13 to 67° from the horizontal axis. The mean absolute error and the area of the 95% confidence ellipse are not significantly correlated with major axis angle (ρ ≤ 0.312) and ellipticity (|r| ≤ 0.343). By simulating shots aimed at the top-right and top-left edges of a goal with these observed ranges and normalised ellipse area, we reveal a wide range of probability of shots on goal (top-right: 2.7-fold difference, top-left: 1.5-fold difference) due to inter-individual variability in error shape and direction independent of error size. Further simulation shows that, depending on the shape-direction combination, the aiming points with the same 80% probability of shots on goal change by up to 0.3 m vertically, even for the same minimal error size. We highlight the importance for football players to consider not only accuracy/precision, but also error shape and direction to optimise motor planning.

A Video App for Screening Osgood-Schlatter Disease Using Soccer Instep Kicking Motion Analysis.

Osgood-Schlatter disease (OSD) is a type of osteochondrosis and traction apophysitis that results from repeated contractions of the quadriceps femoris muscle on the tibial tuberosity. Its prevention, early diagnosis, and treatment are crucial because it causes chronic knee pain and surgical approaches are required if left untreated. Three-dimensional motion analysis is a useful approach for elucidating the pathological factors of OSD; however, it requires advanced cameras, sophisticated facilities, and expensive software. Conversely, the advent of technology has provided affordable video recording devices, and smartphone/tablet-based applications have enabled two-dimensional (2D) motion analysis. This emerging tool and artificial intelligence technology were used to analyze the pivot leg from videos recorded on a tablet device during the instep kicks of adolescent soccer players. Therefore, in this study, we aimed to determine whether the pathological factors for OSD occurring in the pivot foot can be identified through a simple 2D motion analysis using a tablet device. In total, 94 knees of 47 soccer players (aged 14.1±0.8 years, all male) who belong to a single soccer club were evaluated. OSD was diagnosed using ultrasonography and physical examination (a positive bone fragment on ultrasonography or tenderness at the tibial tuberosity). Lower limb muscle tightness was evaluated using the finger-floor distance, straight leg raising test, heel-buttock distance, Thomas test, and ankle range of motion using a goniometer. We then performed motion analysis, and the instep kicking motion was recorded using a video camera on a tablet device. The joint angles of the hip, knee, and ankle were measured using a real-time human-pose detection system. Data were compared between the OSD and non-OSD groups. Overall, six of the 47 players (12.8%) were diagnosed with OSD. No correlation was found between lower limb tightness and the occurrence of OSD in all indices. However, the 2D motion analysis revealed that the knee flexion angle at the time of plantar placement during the instep kick movement was significantly larger in the OSD group than in the non-OSD group (OSD group: 42.0±7.2˚, non-OSD group: 33.5±6.6˚, *p=0.013). A video motion analysis revealed that the knee flexion angle during the instep kicking motion was significantly greater in athletes with OSD of the supporting foot.

Strategic insights into penalty kick execution: A comprehensive analysis of observable behaviors in the German Bundesliga

This study aimed to investigate which observable variables would be able to predict the penalty taker strategy; and to identify the prevalence of the penalty taker strategy in successful penalty kicks. Dataset consists of 220 penalty kicks from the German Bundesliga (2019-2021). Video-based performance analysis of in-match penalty kicks was performed. Chi-squared (χ2) test and logistic regression (enter method) analyses were performed to investigate the relationship between observable behaviors and the penalty-taker strategy. The following behavior: gaze behavior at the ball, no deception, number of steps more than 3, perceived ball speed as powerful shot, run up speed fast, penalty kick shot height at the center or down, kicking technique instep kick, and run up approach frontal was related to the goalkeeper independent strategy (χ2 (177) = 211.049, 96%, p < .001). In successful penalty kicks the independent goalkeeper strategy was more adopted (59.87%). The differentiation between penalty kick patterns provides scientific and practical insights as it enables researchers to identify patterns in the German Bundesliga. Through analysis of the kicker's running pattern, deception actions, gaze behavior, and kicking technique, football practitioners may attempt to determine the kicker's favored approach, and ultimately the penalty kick strategy, so they can inform coaching staff and players.

Determining the influence of dynamic balance in the technical training in football game at U13 level

Background and Study Aim. Technical training in football plays an important part in scoring goals. Precise movements can become the key to victory in a match. Among the principal factors determining the accuracy of shooting or kicking the ball is balance. The study aims to determine the influence of dynamic balance on technical training in U13 football. Material and Methods. A group of 26 football players from Otopeni Sports Club (Romania), aged 12-13 years, in the U13 category, participated in this study. Dynamic balance was assessed using the Sensamove MiniBoard platform with tests including: Lateral bipedal balance (LBB), Vertical bipedal balance (VBB), and Vertical unipedal balance for both right (VBRL) and left (VBLL) legs. Technical training was evaluated using tests recommended by the Romanian Football Federation: instep kick from 9 m (Test 1, points), outside kick in 30 sec. (Test 2, points), and 20 m long pass (Test 3, points). Pearson’s correlation coefficient was used to analyze the relationship between dynamic balance (lateral and vertical bipedal, and vertical unipedal for both legs) and technical training in U13 footballers. Results. The analysis of the comparative results between LBB and VBB variables reveals better performances by 9.2% at VBB. There are lower values of the vertical deviations mean by 2.9 degrees forward at LBB and by -2.8 degrees backward. The mean of lateral deviations is lower by -2.7 degrees to the left at VBB and by 3.3 degrees to the right. The comparative results between VBRL and VBLL variables show better performances by 0.3% at VBRL. The values of the vertical deviations mean are lower by 0.5 degrees forward at VBRL and 0.3 degrees backward. The mean of the lateral deviations (left-right) have equal values. Analyzing the performances obtained in technical tests highlights 22.2% (estimated maximum score) at instep kick, 62.5% (individual maximum value) at outside kick and 34.5% (estimated maximum value) at 20 m long pass. The influence of dynamic balance on technical training shows 60.7% positive connections and 39.3% negative ones between LBB and VBB variables. As for VBRL and VBLL variables, there are 67.9% positive connections and 32.1% negative connections between them. Conclusions. The weighting of values at performance and maintaining in space was highlighted. The mean of front-back and left-right deviations in bipedal and unipedal balance has lower values. The technical performances obtained were compared with the estimated maximum score and the individual maximum value. An increased number of positive connections to balance performance variables and of negative connections to the mean of deviations was noticed. This fact contributed to determining the degree of influence on the investigated variables. The findings can serve as a recommendation for future research.

Different Biomechanics in Football Shooting Using Inside and Instep Kick

This research purposes were examinedthe differences in shooting accuracy using inside and instep kicks and observe differences in kick movements based on biomechanical variables. Twelve professional football players shot using inside and instep kicks on circular hops targets, shooting motions were recorded using a camera at 1000 frames per second. The kinematics during the swing phase and the impact phase with the ball producing the ball’s trajectory were analyzed. Independent t-test used to compare shooting using inside and instep kick. The results showed that there was a significant difference in shooting accuracy using inside and instep kick (tcount = 3.317, p = 0.003) with a effect size large (Cohen’s d = 1.35). When observing the movements, there were significant differences in backswing knee angle (p=0.024), frontswing knee angle (p=0.034), shoulder tilt angle (p=0.045), ball bearing foot placement (p=0.019), and inclination angle of pedestal foot(p = 0.000), while other biomechanical variables showed no significant difference (p > 0.05). This research concludes that accurate shooting movement is achieved using inside kicks, caused by the backswing and frontswing knee angles, body tilt, and the placement and angle of the pedestal foot.

Do non-contact injuries occur during high-speed running in elite football? Preliminary results from a novel GPS and video-based method.

Understanding how injuries occur (inciting circumstances) is useful for developing etiological hypotheses and prevention strategies. The aims of this study were 1) to evaluate the feasibility of a method combining video and Global Positioning System data to estimate the speed and acceleration of activities leading to injuries and 2) to use this method to analyse the inciting circumstances leading to non-contact injuries. Retrospective descriptive study. Injury inciting circumstances from 46 elite players over three seasons were analysed from video recordings and from external load measures collected through Catapult Vector S7 Global Positioning System. In total 34 non-contact injuries were analysed. Sixteen out of the seventeen hamstring injuries occurred when players were running for (median and interquartile range) 16.75 m (8.42-26.65 m) and achieved a peak speed of 29.28 km·h-1 (26.61-31.13 km·h-1) which corresponded to 87.55 % of players' maximal speed (78.5 %-89.75 %). Of the three adductor injuries, one occurred whilst the player was decelerating without the ball, one occurred whilst the player was accelerating and controlling the ball at knee level, and one occurred whilst the player was performing an instep kick. Two quadriceps injuries occurred whilst the players were kicking either whilst walking or running. From the preliminary results reported in this study most hamstring injuries occurred when players ran >25 km·h-1 and above 80 % of their maximal speed. This study suggests that this novel approach can allow a detailed and standardised analysis of injury inciting circumstances.

Effects of Resistance Training of Upper Limb and Trunk Muscles on Soccer Instep Kick Kinematics.

The upper body and trunk muscles are crucial to perform soccer kicks. Resistance training targeting these muscles may modify the pattern adopted during kicking. This study aimed to investigate the effect of resistance training of the arm and anterior trunk muscles on instep kicking kinematics. Twenty-six male participants were randomly allocated into a training group or control group. The training group underwent resistance training of arm and trunk muscles and practiced the instep kick for 8weeks. The control group only practiced kicking during the same period. The trunk, hip, and knee kinematics were assessed during the instep kick before and after the intervention. Kinematics were analyzed according to their data distribution with statistical parametric or nonparametric mapping. The effect of the training on the 1-repetition maximum test was analyzed using a repeated-measures multivariate analysis of variance. The training group showed greater hip extension after the training during the backswing phase (Hedge g effect size of 0.316-0.321) and increased 1-repetition maximum for all exercises. There were no other differences. The present study documented the nonlocal effect of strengthening training in which arm and trunk muscle training resulted in changes in hip kinematics during the backswing phase of the instep kick.

External Focus Reduces Accuracy and Increases Antagonist Muscle Activation in Novice Adolescent Soccer Players.

Instep kick is one of the most effective kicking techniques in soccer. Lower extremity muscles and joints play a crucial role during instep kick. However, external (EF) and internal focus and their effect on the muscles are still ambiguous. In this study, 13 male adolescent soccer players were included and aimed to hit the targets in internal and EF conditions. Lower extremity muscle activations were measured with surface electromyography, and kinematics were measured with a high-speed video camera. Muscle activations and movement latencies were analyzed in four different phases (backswing, leg cocking, acceleration, and follow-through) of kicking. While 10 out of 13 participants kicked accurately in internal focus, only five out of 13 in EF kicked accurately. Gastrocnemius muscle activations increased significantly in EF in all phases except acceleration. Movement latencies were found 0.07 ± 0.002s for accurate and 0.05 ± 0.004s for inaccurate kicks in EF. A correlation has been found between accuracy and movement latency in EF (R = .67). Our results suggest that novices cannot yet coordinate their muscles in EF, cocontraction ratio increases. Therefore, training strategies that aim to reduce the cocontraction ratio can help the athlete increase performance through better motor coordination. Moreover, better motor coordination may be beneficial in preventing injuries (joint stiffness, etc.) caused by increased cocontraction ratio.

Dominant and Nondominant Leg Kinematics During Kicking in Young Soccer Players: A Cross-Sectional Study.

The goal of the study is to analyze the kinematics and provide an EMG analysis of the support limb during an instep kick in adolescent players. We set a video camera, two torque transducers on the knee, and EMG sensors. A sample of 16 adolescent soccer players between 10 and 12years old performed kicks. The kinematics shows a p = .039 on frontal plane (dominant 15.4 ± 1.8, nondominant 18.8 ± 1.7); the EMG analysis shows a p = .04 on muscular activation timing for the vastus medialis. A difference between the legs on the frontal plane emerges. Moreover, a huge difference on sagittal plane between the adolescent pattern and adult pattern exists (15° in adolescent population, 40° in adult population). The result shows a greater activation of the vastus medialis in the nondominant leg; probably, in this immature pattern, the adolescents use this muscle more than necessary.

Comparison of soccer instep kicking kinematics with and without elastic taping

ABSTRACT The present study aimed to determine the effect of elastic taping on soccer instep kicking kinematics. Fifteen male university soccer players performed maximal instep kicking with and without Y-shaped elastic taping on the skin surface of the rectus femoris muscle. Their kicking motions were captured at 500 Hz using a motion capture system. The thickness of the rectus femoris muscle was measured using an ultrasound scanner prior to the kicking session. The thickness of the rectus femoris muscle and kicking leg kinematics in both the conditions were compared. The thickness of the rectus femoris muscle increased significantly after elastic tape application. In conjunction with this change, kinematic variables of the kicking leg, such as peak hip flexion angular velocity and knee and foot linear velocities significantly increased. However, there was no change in the knee extension angular and hip linear velocities. The elastic tape application caused deformation of the rectus femoris muscle and improvement of the instep kicking performance. The study findings provide a new insight on the effect of elastic taping on dynamic sports performance, such as in soccer instep kicking.

Sex difference in soccer instep kicking

ABSTRACT We aimed to clarify the differences in soccer instep kicking dynamics between sex groups. The instep kicking of seven female (height: 160.3 ± 6.1 cm; mass: 54.3 ± 5.2 kg) and seven male (height: 173.0 ± 5.9 cm; mass: 70.0 ± 9.0 kg) players were recorded by a motion capture system (500 Hz). Joint moments of the kicking leg were computed and normalized by the body mass and height. Statistical parametric mapping was used to compare the entire kicking motion between the two groups. Significantly slower resultant ball velocity seen in female players was most likely explained by their significantly slower run-up velocity, shorter leg length and lower foot–ball velocity ratio. Female players exhibited significantly smaller knee joint moment in the latter part (80–86%) of kicking. Also, significantly smaller positive work done by knee extension moment and the ratio of work (knee extension/hip flexion) were found in female players. These results suggested that the suppressed knee extension moment action was identified as a key kinetic characteristic in the instep kicking of female players, and to compensate for this action, they more rely on the work due to hip flexion moment to execute the instep kicking.

Differences in lower leg kinetics of soccer instep kicking between female and male players

ABSTRACT We aimed to clarify the difference in lower leg segment kinetics of soccer instep kicking between female and male players. Instep kicking motions of seven female and seven male university soccer players were captured at 500 Hz. Lower leg angular velocity, knee joint moment and the interaction moment acting on the lower leg were calculated. Discrete variables were compared using two sample-t-test, and statistical parametric mapping were used to compare the time-series changes between the two groups. Although female players maintained a comparable magnitude of lower leg angular velocity, they exhibited significantly lower knee extension moment in the latter part of kicking and significantly smaller forward angular impulse due to that moment. In contrast, female players were found to have a comparable magnitude of angular impulse due to forward component of interaction moment to that of male players. Eventually, female players come to have significantly larger ratio of angular impulses (forward interaction moment/knee extension moment) than male players. It can be considered that the forward component of interaction moment acting on the lower leg of female players may compensate their reduced exertion of knee extension moment, thereby achieving a comparable lower leg angular velocity to that of male players.

Foot dominance and ball approach angle affect whole-body instep kick kinematics in soccer players

ABSTRACT 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.

Motion Analysis of Football Kick Based on an IMU Sensor.

A greater variety of technologies are being applied in sports and health with the advancement of technology, but most optoelectronic systems have strict environmental restrictions and are usually costly. To visualize and perform quantitative analysis on the football kick, we introduce a 3D motion analysis system based on a six-axis inertial measurement unit (IMU) to reconstruct the motion trajectory, in the meantime analyzing the velocity and the highest point of the foot during the backswing. We build a signal processing system in MATLAB and standardize the experimental process, allowing users to reconstruct the foot trajectory and obtain information about the motion within a short time. This paper presents a system that directly analyzes the instep kicking motion rather than recognizing different motions or obtaining biomechanical parameters. For the instep kicking motion of path length around 3.63 m, the root mean square error (RMSE) is about 0.07 m. The RMSE of the foot velocity is 0.034 m/s, which is around 0.45% of the maximum velocity. For the maximum velocity of the foot and the highest point of the backswing, the error is approximately 4% and 2.8%, respectively. With less complex hardware, our experimental results achieve excellent velocity accuracy.

Defining movement strategies in soccer instep kicking using the relationship between pelvis and kick leg rotations

ABSTRACT Growing evidence suggests skilled ball kickers use distinct pelvis and kick leg strategies to achieve successful performance. However, since the interaction between different strategies remains unexplored, the aims of this study were to a) examine relationships between pelvis and kick leg rotations in male players performing soccer instep kicks and b) classify different ‘types’ of kickers based on the observed movement strategies. Twenty semi-professional players performed kicks for maximal speed and accuracy, and kick leg and pelvis kinematics were analysed using 3D motion capture (1000 Hz). A strong relationship was found between change in pelvis transverse angular velocity and thigh-knee angular velocity ratio upon ball contact (r = 0.76, p < 0.001), and participants were categorised by their location on kick leg (thigh-knee) and pelvis (maintainer-reverser) continuums. Knowledge of a player’s preferred strategy can inform departure from ‘one size fits all’ technical and conditioning training practices towards more individualised approaches. For example, pelvis maintainer-thigh dominant kickers might benefit from focus towards the concentric capabilities of the hip flexors, whereas reverser-knee dominant kickers might benefit from developing the ability to decelerate the pelvis and thigh to induce motion-dependent angular acceleration of the lower leg towards the ball.

A Data Analytics Approach to Assess the Functional and Physical Performance of Female Soccer Players: A Cohort Design.

Background and Objectives: The aim of this study was twofold: (i) to observe the individual results of fitness status [countermovement jump (CMJ)], hop test, linear sprinting time, stride frequency, stride distance, force–power–velocity, peak power maximal and maximal speed, and repeated sprint ability (RSA) and functional performance (overhead squat, single-leg squat test, dumbbell hip-hinge, Thomas test, hip extension, and internal and external hip rotators) and (ii) to analyze the relationship between anthropometrical measures and values of fitness status with % of difference in the Thomas test, hip extension, and internal and external hip rotators. Materials and Methods: The study followed a cohort design. Sixteen female soccer players competing in the second division of the Spanish league were monitored during the first days of the pre-season. These players were evaluated three times during the preseason of the cohort period. The dataset showed a negative moderate correlation between time and percentage of difference in hip angle and another positive moderate correlation between maximal sprint and percentage of difference in hip angle (r = −0.54, p = 0.02 and r = 0.53, p = 0.04), respectively. The correlations of stride time and distance with hip extension are interesting, as professional soccer players should have higher levels of hip flexor flexibility during the stride phase, recoil of the instep kick action.

Analysis of the ball speed in the kick of futsal players as a function of the contact instep of the lower limbs

In order to identify the variation of the ball speed in kicks performed with different contact faces in futsal, 30 athletes were evaluated, who performed three kicks with the inside face, back and toe, of the 10-meter shot, separating the dominant and non-dominant sides. A BUSHNELL speed radar, model 101911, measuring in km/h was used. Statistical tests were performed and the results showed statistical differences in toe and instep kicks, with velocity greater than the inner instep in both dominant and non-dominant. These findings help in training planning, with the aim of increasing the effectiveness of this motor action.

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

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

Effects of wearing knee-guards on skin pressure and skin blood flow during dynamic motions

The purpose of the present study was to explore the effects of wearing knee guards on skin blood flow and skin pressure during dynamic soccer motions. Twenty-one male subjects participated in the following two experimental conditions: wearing knee guards (KG) and no knee guards (Control). Subjects performed several consecutive soccer motions along with a standing position between each motion. Skin blood flow and skin pressure on the thigh, knee, and calf were monitored. The results showed that skin pressure had the greatest value in a sitting position for both the KG condition and Control, but the smallest during instep kicking and switching directions (P < 0.001). The rear calf had the greatest skin pressure for the KG condition (P < 0.001), while the side knee showed the greatest for the Control (P < 0.001). Normalized skin blood flow based on values from their standing position was the greatest during the jump motion among the various soccer motions. Interestingly, skin blood flow decreased by wearing the knee guards on the front thigh and calf (r = − 0.859; r = − 0.835; P < 0.001), while the blood flow increased on the side knee (r = 0.295, P < 0.001). Subjects felt greater skin pressure sensation during the jump motion and switching directions than other soccer positions/motions (P < 0.001). These results indicate that the knee guards result in relatively lighter pressure for dynamic motions (e.g., kick, switching directions, or jump) than for static positions (e.g., sitting or standing), and the skin blood flows for the thigh, knee, and calf are redistributed by wearing the knee guards, especially during jumping.

Effect of support foot placement on football instep kick performance

ABSTRACT Although the support foot plays an important role in kicking a football, there has been a paucity of research exploring the effect of the placement of the support foot on kicking performance. To investigate the kick performance under different support foot positions, ten male footballers were recruited to participate in two experiments: one determining the maximum ball speed and the second determining accuracy. The participants were instructed to plant their support foot on one of nine different spots marked in the form of a 3 × 3 shape on a piece of artificial grass and asked to kick the ball. In the first (maximum speed) test, the participants tried their best to kick the ball at the maximum ball speed from nine different support foot positions. In the second (accuracy) test, the participants kicked the ball toward the target area without restricting the support foot position. The ball speed, as well as the success rate, were recorded from each support foot position. Significantly higher ball speed and accuracy were obtained at medial positions than was the case at lateral positions from the nine spots. It was concluded that although footballers may choose different positions for support foot placement, the maximum ball speed and better accuracy could be expected when the support foot was next to or slightly in front of the ball centre without too much side-by-side separation (27–37 cm).