Der Einfluss des Fußballschuhs auf die Schussgeschwindigkeit beim Vollspannstoß

Einleitung: Der Vollspannstoß im Fußball ist die Schusstechnik, mit der die höchste Ballgeschwindigkeit erzielt wird. Ein höheres Gewicht von Fußballschuhen verringert die Geschwindigkeit des Schussfußes (Amos und Morag 2002). Die Ballgeschwindigkeit beim Vollspannstoß unterliegt dem Einfluss unterschiedlicher Fußballschuhmodelle (Hennig und Zulbeck 1999). Das Ziel der vorliegenden Untersuchungsreihe war es, den Einfluss des Fußballschuhs auf die Schussgeschwindigkeit beim Vollspannstoß zu untersuchen. Methodik: In neun Einzelstudien wurden unterschiedliche Eigenschaften von Fußballschuhen isoliert auf ihre Wirkung bezüglich der Schussgeschwindigkeit beim Vollspannstoß untersucht. Die Studien wurden als Laborexperimente durchgeführt. Grundlegende Untersuchungsaspekte waren unterschiedliche Traktionsverhältnisse beim Standbeinaufsatz, das Schießen mit und ohne Schuh sowie die Reibungsverhältnisse zwischen Ball und Schuhmaterial. Weitere Untersuchungsgegenstände waren der Einfluss verschiedener Schuhmodelle auf die Ballgeschwindigkeit, das Schuhgewicht, die Steifigkeit der Außensohle, die Zehenboxhöhe sowie die Bequemlichkeit. Zudem wurde untersucht, inwiefern Fußballspieler ihre erzielte Ballgeschwindigkeit in Abhängigkeit von der Schuhbedingung einschätzen können. Zur Durchführung der Einzelstudien führten etwa 20 Fußballspieler sechs maximale Vollspannstöße in allen spezifischen Schussbedingungen der jeweiligen Studie durch. Die Ballgeschwindigkeit wurde mittels einem Radarpistolensystem gemessen. Die statistische Auswertung geschah mittels der einfaktoriellen Varianzanalyse für abhängige Stichproben und Post-Hoc t-Tests nach Fisher’s PLSD. Ergebnisse: Die Traktion des Standbeins war ein wichtiger Einflussfaktor für eine hohe Ballgeschwindigkeit (p<0,01). Das barfüßige Schießen war gegenüber drei verschiedenen verwendeten Schuhbedingungen überlegen (p=0,05). Die Reibungsverhältnisse zwischen Ball und Schuhmaterial sind statistisch nicht entscheidend für die erzielte Ballgeschwindigkeit (p=0,07). Signifikante Unterschiede wurden allgemein zwischen unterschiedlichen Schuhmodellen hinsichtlich der Ballgeschwindigkeit festgestellt (p<0,01 und p<0,05). Der Einfluss des Schuhgewichts war nicht ausschlaggebend für die resultierende Ballgeschwindigkeit (p=0,29). Zwischen der Steifigkeit der Außensohle und der Ballgeschwindigkeit beim Vollspannstoß zeigte sich kein genereller Zusammenhang (p=n.s.). Einen negativen Einfluss auf die Ballgeschwindigkeit bewirkte die Erhöhung der Zehenbox von Fußballschuhen (p<0,01). Eine verbesserte Bequemlichkeit von Fußballschuhen an der Fersenkappe führte nicht zu einer Erhöhung der erzielten Ballgeschwindigkeit (p=n.s.). Schlussfolgerung: Der Fußballschuh nimmt entscheidenden Einfluss auf die Ballgeschwindigkeit beim Vollspannstoß sowohl am Standbein als auch am Spielbein. Ein Zusammenspiel verschiedener materialtechnischer und geometrischer Faktoren der einzelnen Schuhkomponenten ist zur Erzielung der maximalen Ballgeschwindigkeit notwendig. Zukünftige Studiengegenstände zur Schussgeschwindigkeit können der Einflug der Passform des Schuhs sowie der Einfluss innovativer Schuhobermaterialien mit Rückstellfähigkeit sein

KINEMATIC COMPARISON OF KICKING A STATIONARY AND ROLLING BALL

Much biomechanical research has examined stationary ball kicking in soccer. However, most kicks in games are performed on a rolling ball. It is important to evaluate this kick as findings for stationary ball kicking might not transfer. The aim of this study was to compare stationary and rolling ball kicks. Nine skilled soccer players performed three kicks under four pre-kick ball conditions (stationary, rolling 30? relative to kick direction, rolling 90? relative to kick direction, dribbling). Lower body kinematics were captured using VICON Nexus (250 Hz), analysed in Visual 3D and compared via a factorial ANOVA. No significant difference existed for foot speed at ball contact, or leg kinematics between stationary and rolling ball conditions Further, kinematics did no change regardless of the approach angle of the ball indicating kinematics do not change regardless of pre-kick ball conditions. Future stationary-rolling ball comparison work should examine kinetics, support leg mechanics and foot to ball interaction

INFLUENCE OF FOOTWEAR ON FOOT SENSITIVITY: A COMPARISON BETWEEN BAREFOOT AND SHOD SPORTS

The purpose of this study was to compare the vibration thresholds of the sensor of the plantar foot between athletes that practice sport with shoes and athletes that practice sport without shoes. Fourty female subjects were divided in two groups: Shod group (SG) with 20 volleyball players and barefoot group (BG) with 20 gymnasts. Vibration thresholds were measured by the use of a vibration exciter at five points of the foot sole: Heel; Midfoot; Metatarsal Head I; Metatarsal Head V and Hallux. The amplitude of the vibration stimulus was raised until it could be perceived by the subjects, which responded with a verbal sign. The amplitude read at the verbal sign was taken as the vibration threshold. The results show significantly lower vibration threshold values for the BG (p< 0.001) when calculating the mean values of the five foot points. The vibration thresholds measured at each of the five selected foot points were lower for the BG in comparison with the SG. However those differences were not statistically significant. The results indicate that the higher vibration sensitivity at the plantar foot for the BG may be explained by the sport practice without footwear as well as by the technical demands of the sport

Biomechanical locomotion adaptations on uneven surfaces can be simulated with a randomly deforming shoe midsole

Background: A shoe with unsystematic perturbations, similar to natural uneven terrain, may offer an enhanced training stimulus over current unstable footwear technologies. This study compared the instability of a shoe with unpredictably random midsole deformations, an irregular surface and a control shoe-surface whilst treadmill walking and running. Methods: Three-dimensional kinematics and electromyography were recorded of the lower limb in 18 active males. Gait cycle characteristics, joint angles at initial ground contact and maximum values during stance, and muscle activations prior to initial contact and during loading were analysed. Perceived stability, injury-risk and energy consumption were evaluated. Instability was assessed by movement variability, muscular activations and subjective ratings. Results: Posture alterations at initial contact revealed active adaptations in the irregular midsole and irregular surface to maintain stability whilst walking and running. Variability of the gait cycle and lower limb kinematics increased on the irregular surface compared to the control across locomotion types. Similarly increased variability (coefficient of variation) were found in the irregular midsole compared to the control for frontal ankle motion (walk: 31.1 and 14.9, run: 28.1 and 11.6), maximum sagittal knee angle (walk: 7.6 and 4.8, run: 2.8 and 2.4), and global gait characteristics during walking only (2.1 ± 0.5 and 1.6 ± 0.3). Tibialis anterior pre-activation reduced and gastrocnemius activation increased in the irregular midsole compared to the control across locomotion types. During running, peroneus longus activation increased in the irregular midsole and irregular surface. Conclusions: Results indicate random shoe midsole deformations enhanced instability relative to the control and simulated certain locomotion adaptations of the irregular surface, although less pronounced. Thus, a shoe with unpredictable instability revealed potential as a novel instability-training device

CONTRIBUTION OF THE SUPPORT LEG TO ACCELERATE KICKING LEG SWING DURING SOCCER INSTEP KICKING

The present study aimed to determine the contribution of support leg motion to the acceleration of the kicking leg in soccer instep kicking. The kicking motion was recorded by a motion capture system. According to the procedures proposed in previous studies, the power due to the muscle and interaction moments acting on the kicking lower leg was computed. The forward swing of the lower leg during the final phase of kicking was dominated by the power of the interaction moment rather than by that of the muscle moment. The support leg motion contributed to produce more than 50 % of the total amount of positive work due to the power of the interaction moment. The present study proposed a reasonable mechanism for the acceleration of the lower leg swing when its angular velocity exceeds the inherent force-velocity limitation of muscles

KINETIC ANALYSIS OF THE SUPPORT LEG IN SOCCER INSTEP KICKING

The purpose of the present study was to illustrate the kinetic aspect of the support leg during soccer instep kicking. The motion was captured together with the ground reaction force using a motion capture system. Moments and angular velocities of ankle, knee and hip joint for the support leg were calculated. The ankle joint was passively rotated threedimensionally, during which these motions were counteracted to the joint moments. The knee joint motion, likewise, counteracted to the joint moment from the instant of the touch-down to just before ball impact. It is likely that the ankle and knee joints have a role in attenuating the impact of landing. In contrast, positive power due to the knee and hip extension moments appeared just before ball impact. It can be assumed that those motions may serve to lift the body thereby indirectly contributing the kick leg swing

The influence of sprint spike bending stiffness on sprinting

There is evidence that increasing the longitudinal bending stiffness of sprinting footwear can lead to improved sprinting performance although this has not yet been established. This study examined the effect of four known shoe stiffness conditions on both sprinting performance and metatarsophalangeal joint (MTPJ) motion. Twelve trained sprinters performed 40 m maximal sprints along an indoor running track, two sprints in each stiffness condition, and high-speed video (600 Hz) recorded two-dimensional MTPJ motion during ground contact. To explore individual responses to the footwear manipulations, three-dimensional (1000 Hz) kinematic and kinetic data were collected during maximal sprinting for two sprinters. At the group-level, increasing shoe bending stiffness elicited no significant differences in sprinting performance or MTPJ motion, with any changes between conditions being subject-specific. In-depth individual analyses revealed that increased shoe stiffness could restrict motion about the MTPJ and there appeared to be a preferred stiffness for best performance. This notion of individual optimal sprint shoe stiffness and what factors might contribute to the optimum requires further investigation