Quadriceps EMG muscle activation during accurate soccer instep kicking

Six competitive soccer players were recruited to examine EMG activation in three quadriceps muscles during a kicking accuracy task. Participants performed three maximum instep place kicks of a stationary ball, 11 m perpendicular from the centre of the goal line towards targets (0.75 m(2)) in the four corners of the goal. Surface EMG of the vastus lateralis, vastus medialis, and rectus femoris of the kicking leg was normalized and averaged across all participants to compare between muscles, targets, and the phase of the kick. Although no significant difference were observed between muscles or kick phases, kicks to the right targets produced significantly greater muscle activity than those towards the left targets (P < 0.01). In addition, kicks towards the top right target demonstrated significantly greater muscle activity than towards the top and bottom left (P < 0.01). Under accurate soccer shooting conditions, kicks aimed to the top right corner of the goal demonstrated a higher level of quadriceps muscle activation than those towards the other corners.     

Early visual cues associated with a directional place kick in soccer

The purpose of this paper was to establish postural cues in kicking that may be of use to goalkeepers. Eight male soccer players (age 20.5 ± 1.1 yrs; height 1.78 ± 0.053 m; mass 75.18 ± 9.66 kg) performed three types of kick: a low side-foot kick to the left hand corner of the goal, a low side-foot kick straight ahead, and a low instep kick straight ahead. Kicks were recorded by an optoelectronic motion analysis system at 240 Hz. At kicking foot take-off (about 200 ms before ball contact) the variables which were significantly different and could act as cues were support foot progression angle, pelvis rotation, and kicking hip and ankle flexion. The support foot progression angle was considered to be the most valuable of these variables as its angle coincided with the direction of ball projection. The other variables were less clear in their interpretation and so less valuable for a goalkeeper to use for decision making. Cues appearing after support foot contact were thought unlikely to be of value to a goalkeeper in their decision making. These include kicking leg knee flexion angle, and support leg shank and thigh angles.     

Is soccer kick performance better after a "faking" (cutting) maneuver task?

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.     

Three-dimensional kinematics and ground reaction forces during the instep and outstep soccer kicks in pubertal players

Abstract

The purpose of the present study was to compare the three-dimensional kinematics of the lower extremities and ground reaction forces between the instep kick and the kick with the outside area of the foot (outstep kick) in pubertal soccer players. Ten pubertal soccer players performed consecutive kicking trials in random order after a two-step angled approach with the instep and the outstep portion of the foot. Three-dimensional data and ground reaction forces were measured during kicking. Paired t-tests indicated significantly higher (P < 0.05) ball speeds and ball/foot speed ratios for the instep kick compared with the outstep kick. Non-significant differences in angular and linear sagittal plane kinematic parameters, temporal characteristics, and ground reaction forces between the instep and outstep soccer kicks were observed (P > 0.05). In contrast, analysis of variance indicated that the outstep kick displayed higher hip internal rotation and abduction, knee internal rotation, and ankle inversion than the instep kick (P < 0.05). Our results suggest that the instep kick is more powerful than the outstep kick and that different types of kick require different types of skill training.     

Dynamics of submaximal effort soccer instep kicking

During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.     

Acute and sub-acute effects of repetitive kicking on hip adduction torque in injury-free elite youth soccer players

Abstract

Hip adduction strength is important for kicking and acceleration in soccer players. Changes in hip adduction strength may therefore have an effect on soccer players’ athletic performance. The purpose of this study was to investigate the acute and sub-acute effects of a kicking drill session on hip strength, concerning isometric hip adduction, abduction and flexion torque of the kicking leg and the supporting leg. Ten injury-free male elite soccer players, mean ± s age of 15.8 ± 0.4 years participated. All players underwent a specific 20 min kicking drill session, comprising 45 kicks. The players were tested the day before, 15 min after and 24 h after the kicking drill session by a blinded tester using a reliable test procedure. The isometric hip-action and leg-order were randomized. For the kicking leg, hip adduction torque increased from 2.45 (2.19–2.65) Nm ? kg^?1, median (25th–75th percentiles), at pre-kicking to 2.65 (2.55–2.81) Nm ? kg^?1 (P = 0.024) 24 h post-kicking. This may have implications for the soccer player’s ability to maximally activate the hip adductors during kicking and acceleration, and thereby improve performance the day after a kicking drill session.     

Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players

The players' ability to achieve the greatest distance in kicking is determined by their efficiency in transferring kinetic energy from the body to the ball. The purpose of this study was to compare the kinetics and kinematics of the plant leg position between male and female collegiate soccer players during instep kicking. Twenty-three soccer players (11 males and 12 females) were filmed in both the sagittal and posterior views while performing a maximal instep kick. Plant leg kinetic data were also collected using an AMTI 1000 force platform. There were no significant differences between the sexes in plant leg position, but females had significantly greater trunk lean, plant leg angle, and medial-lateral ground reaction force than the males. Males showed higher vertical ground reaction forces at ball contact, but there were no significant differences in ball speed at take-off between the sexes. Ball speed at take-off was inversely related to peak anterior–posterior ground reaction force ( ? 0.65). The anatomical differences between the sexes were reflected in greater trunk lean and lower leg angle in the females.     

Kinetic comparison of a side-foot soccer kick between experienced and inexperienced players

The aim of this study was to identify critical kinetic variables that lead to increased ball velocity during a side-foot passing kick in soccer. Seven experienced male soccer players and eight inexperienced players participated in the experiment. They were instructed to perform side-foot kicks along the ground with maximum effort with an eye on the target line. The joint angles, angular velocities, and torques of the kicking leg were determined based on the three-dimensional kinematic data. The mean ball speed of the experienced group (21.4 +/- 1.5 m/s) was significantly faster than that of the inexperienced group (16.0 +/- 1.0m/s; P < 0.001). The motions of the inexperienced players tended to be less dynamic than those of the experienced players. The most noticeable difference in the kinetics of the kick was found in the hip flexion torque throughout the back-swing phase until the leg-cocking phase. The mean peak value of the experienced group (168 +/- 20 N x or m) was significantly greater than that of the inexperienced group (94 +/- 17 N x or m; P < 0.001). To increase ball speed during a side-foot passing kick, the generation of hip-flexion torque during the earlier stage of kicking is critical.     

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

The aims of this study were to examine the release speed of the ball in maximal instep kicking with the preferred and the non-preferred leg and to relate ball speed to biomechanical differences observed during the kicking action. Seven skilled soccer players performed maximal speed place kicks with the preferred and the non-preferred 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.     

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

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

Early visual cues associated with a directional place kick in soccer

The purpose of this paper was to establish postural cues in kicking that may be of use to goalkeepers. Eight male soccer players (age 20.5 +/- 1.1 yrs; height 1.78 +/- 0.053 m; mass 75.18 +/- 9.66 kg) performed three types of kick: a low side-foot kick to the left hand corner of the goal, a low side-foot kick straight ahead, and a low instep kick straight ahead. Kicks were recorded by an optoelectronic motion analysis system at 240 Hz. At kicking foot take-off (about 200 ms before ball contact) the variables which were significantly different and could act as cues were support foot progression angle, pelvis rotation, and kicking hip and ankle flexion. The support foot progression angle was considered to be the most valuable of these variables as its angle coincided with the direction of ball projection. The other variables were less clear in their interpretation and so less valuable for a goalkeeper to use for decision making. Cues appearing after support foot contact were thought unlikely to be of value to a goalkeeper in their decision making. These include kicking leg knee flexion angle, and support leg shank and thigh angles.     

Adductor longus mechanics during the maximal effort soccer kick

Groin pain is a common cause of athletic disability and often involves the adductor longus. A common complaint of patients with groin problems is pain while preparing to kick the ball. The purpose of this study was to examine muscle length and activation of the adductor longus while kicking a soccer ball. Three-dimensional joint positions and muscle activation were obtained from 15 National Collegiate Athletic Association (NCAA) Division 1 male soccer players during maximal effort kicks. Musculoskeletal modeling techniques incorporating joint position and muscle attachments were used to estimate adductor longus length from the beginning of the kicking leg's swing phase until ball strike. The maximum rate of stretch of the adductor longus (22.3 ± 5.3 cm/s) and maximum hip extension (23.3 ± 8.8°) occurred near 40% of swing phase. Activation of the adductor longus occurred between 10% and 50% of the swing phase. Adductor longus maximum length occurred at 65% of the swing phase. Maximum hip abduction (25.3 ± 5.4°) occurred at 80% of swing phase. The adductor longus appears to be at risk of strain injury during its transition from hip extension to hip flexion. This knowledge could be applied to muscle injury prevention and rehabilitation programs to aid with treatment of adductor longus related groin pain.     

Mechanical factors associated with the development of high ball velocity during an instep soccer kick

The purpose of this study was to determine whether joint velocities and segmental angular velocities are significantly correlated with ball velocity during an instep soccer kick. We developed a deterministic model that related ball velocity to kicking leg and pelvis motion from the initiation of downswing until impact. Three-dimensional videography was used to collect data from 16 experienced male soccer players (age = 24.8 ± 5.5 years; height = 1.80 ± 0.07 m; mass = 76.73 ± 8.31 kg) while kicking a stationary soccer ball into a goal 12 m away with their right foot with maximal effort. We found that impact velocities of the foot center of mass (CM), the impact velocity of the foot CM relative to the knee, peak velocity of the knee relative to the hip, and the peak angular thigh velocity were significantly correlated with ball velocity. These data suggest that linear and angular velocities at and prior to impact are critical to developing high ball velocity. Since events prior to impact are critical for kick success, coordination and summation of speeds throughout the kicking motion are important factors. Segmental coordination that occurs during a maximal effort kick is critical for completing a successful kick.     

Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players

The players' ability to achieve the greatest distance in kicking is determined by their efficiency in transferring kinetic energy from the body to the ball. The purpose of this study was to compare the kinetics and kinematics of the plant leg position between male and female collegiate soccer players during instep kicking. Twenty-three soccer players (11 males and 12 females) were filmed in both the sagittal and posterior views while performing a maximal instep kick. Plant leg kinetic data were also collected using an AMTI 1000 force platform. There were no significant differences between the sexes in plant leg position, but females had significantly greater trunk lean, plant leg angle, and medial-lateral ground reaction force than the males. Males showed higher vertical ground reaction forces at ball contact, but there were no significant differences in ball speed at take-off between the sexes. Ball speed at take-off was inversely related to peak anterior-posterior ground reaction force (-0.65). The anatomical differences between the sexes were reflected in greater trunk lean and lower leg angle in the females.     

Three-dimensional kinematic correlates of ball velocity during maximal instep soccer kicking in males

Abstract

Achieving a high ball velocity is important during soccer shooting, as it gives the goalkeeper less time to react, thus improving a player's chance of scoring. This study aimed to identify important technical aspects of kicking linked to the generation of ball velocity using regression analyses. Maximal instep kicks were obtained from 22 academy-level soccer players using a 10-camera motion capture system sampling at 500 Hz. Three-dimensional kinematics of the lower extremity segments were obtained. Regression analysis was used to identify the kinematic parameters associated with the development of ball velocity. A single biomechanical parameter; knee extension velocity of the kicking limb at ball contact Adjusted R² = 0.39, p ≤ 0.01 was obtained as a significant predictor of ball-velocity. This study suggests that sagittal plane knee extension velocity is the strongest contributor to ball velocity and potentially overall kicking performance. It is conceivable therefore that players may benefit from exposure to coaching and strength techniques geared towards the improvement of knee extension angular velocity as highlighted in this study.     

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

Abstract

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

Three-dimensional kinematic differences between the preferred and non-preferred limbs during maximal instep soccer kicking

Abstract

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 paired t-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.     

Support leg action can contribute to maximal instep soccer kick performance: an intervention study

This investigation assessed whether a Technique Refinement Intervention designed to produce pronounced vertical hip displacement during the kicking stride could improve maximal instep kick performance. Nine skilled players (age 23.7 ± 3.8 years, height 1.82 ± 0.06 m, body mass 78.5 ± 6.1 kg, experience 14.7 ± 3.8 years; mean ± SD) performed 10 kicking trials prior to (NORM) and following the intervention (INT). Ground reaction force (1000 Hz) and three-dimensional motion analysis (250 Hz) data were used to calculate lower limb kinetic and kinematic variables. Paired t-tests and statistical parametric mapping examined differences between the two kicking techniques across the entire kicking motion. Peak ball velocities (26.3 ± 2.1 m · s^?1 vs 25.1 ± 1.5 m · s^?1) and vertical displacements of the kicking leg hip joint centre (0.041 ± 0.012 m vs 0.028 ± 0.011 m) were significantly larger (P < 0.025) when performed following INT. Further, various significant changes in support and kicking leg dynamics contributed to a significantly faster kicking knee extension angular velocity through ball contact following INT (70–100% of total kicking motion, P < 0.003). Maximal instep kick performance was enhanced following INT, and the mechanisms presented are indicative of greater passive power flow to the kicking limb during the kicking stride.     

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

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

Hip adductor activations during run-to-cut manoeuvres in compression shorts: implications for return to sport after groin injury

Abstract

Athletes at high risk of groin strains in sports such as hockey and soccer often choose to wear shorts with directional compression to aid in prevention of or recovery from hip adductor strains. Large, eccentric contractions are known to result in or exacerbate strain injuries, but it is unknown if these shorts have a beneficial effect on hip adductor muscle activity. In this study, surface electromyography (EMG) of the adductor longus and ground reaction force (GRF) data were obtained simultaneously on 29 healthy individuals without previous history of serious injury while performing unanticipated 45° run-to-cut manoeuvres in a laboratory setting wearing shorts with non-directional compression (control, HeatGear, Under Armour, USA) or shorts with directional compression (directional, CoreShort PRO, Under Armour, USA), in random order. Average adductor activity in the stance leg was significantly lower in the directional condition than in the control condition during all parts of stance phase (all P < 0.042). From this preliminary analysis, wearing directional compression shorts appears to be associated with reduced stance limb hip adductor activity. Athletes seeking to reduce demand on the hip adductors as they approach full return to activities may benefit from the use of directional compression shorts.