The effect of muscle fatigue on instep kicking kinetics and kinematics in association football

The aim of this study was to examine the effect of leg muscle fatigue on the kinetics and kinematics of the instep football kick. Fatigue was induced by repeated, loaded knee extension (40% body weight) and flexion (50% body weight) motions on a weight-training machine until exhaustion. The kicking motions of seven male players were captured three-dimensionally at 500 Hz before and immediately after the fatigue protocol. The significantly slower ball velocity observed in the fatigue condition was due to both reduced lower leg swing speed and poorer ball contact. The reduced leg swing speed, represented by a slower toe linear velocity immediately before ball impact and slower peak lower leg angular velocity, was most likely due to a significantly reduced resultant joint moment and motion-dependent interactive moment during kicking. These results suggest that the specific muscle fatigue induced in the present study not only diminished the ability to generate force, but also disturbed the effective action of the interactive moment leading to poorer inter-segmental coordination during kicking. Moreover, fatigue obscured the eccentric action of the knee flexors immediately before ball impact. This might increase the susceptibility to injury.     

Primary mechanical factors contributing to foot eversion moment during the stance phase of running

Rearfoot external eversion moments due to ground reaction forces (GRF) during running have been suggested to contribute to overuse running injuries. This study aimed to identify primary factors inducing these rearfoot external eversion moments. Fourteen healthy men ran barefoot across a force plate embedded in the middle of 30-m runway with 3.30 ± 0.17 m · s^–1. Total rearfoot external eversion/inversion moments (Mtot) were broken down into the component Mxy due to medio-lateral GRF (Fxy) and the component Mz due to vertical GRF (Fz). Ankle joint centre height and medio-lateral distance from the centre of pressure to the ankle joint centre (a_cop) were calculated as the moment arm of these moments. Mxy dominated Mtot just after heel contact, with the magnitude strongly dependent on Fxy, which was most likely caused by the medio-lateral foot velocity before heel contact. Mz then became the main generator of Mtot throughout the first half of the stance phase, during which a_cop was the critical factor influencing the magnitude. Medio-lateral foot velocity before heel contact and medio-lateral distance from the centre of pressure to the ankle joint centre throughout the first half of the stance phase were identified as primary factors inducing the rearfoot external eversion moment.     

Ankle taping can reduce external ankle joint moments during drop landings on a tilted surface

Ankle taping is commonly used to prevent ankle sprains. However, kinematic assessments investigating the biomechanical effects of ankle taping have provided inconclusive results. This study aimed to determine the effect of ankle taping on the external ankle joint moments during a drop landing on a tilted surface at 25°. Twenty-five participants performed landings on a tilted force platform that caused ankle inversion with and without ankle taping. Landing kinematics were captured using a motion capture system. External ankle inversion moment, the angular impulse due to the medio-lateral and vertical components of ground reaction force (GRF) and their moment arm lengths about the ankle joint were analysed. The foot plantar inclination relative to the ground was assessed. In the taping condition, the foot plantar inclination and ankle inversion angular impulse were reduced significantly compared to that of the control. The only component of the external inversion moment to change significantly in the taped condition was a shortened medio-lateral GRF moment arm length. It can be assumed that the ankle taping altered the foot plantar inclination relative to the ground, thereby shortening the moment arm of medio-lateral GRF that resulted in the reduced ankle inversion angular impulse.     

Recollections of Expo 70: Visitors' Experiences and the Retention of Vivid Long‐Term Memories

Abstract This study reports on outcomes of an investigation of visitors' longterm memories of the 1970 Japan World Exposition, Osaka. The paper reports in two parts the emergent outcomes of a study that provides understanding of the nature of visitors' long‐term memories of their experiences in an informal leisure‐time context. First, the paper discusses the common and most dominant recollections that emerged from 48 visitors' memories of this event 34 years ago. An overall explication of visitors' memories of their experiences of the event reveals an interesting mix of reactions: wonderment about the world and the amazing technological advances of the era, blended with personal discomfort and frustrations associated with the memories. These mixed feelings are presented against the backdrop of Japanese national identity re‐emergent on the world stage. Second, an analysis and discussion of qualitative data provides case examples of how three psychological and behavioral factors (affect, agenda fulfillment, and rehearsal) shape the vividness of episodic and/or autobiographical memories of the episodes as they are recalled 34 years later. This paper vividly illustrates the power of qualitative data to illuminate understanding of visitors' long‐term memories and presents some significant issues for museum staff to consider as they plan for visitor experiences that will have lasting impact.     

Internal and external discipline: The effect of project leadership and government monitoring on the performance of publicly funded R&D consortia

R&D consortia have been regarded as an effective means of promoting innovation. Several R&D consortia obtain public financial support, which may affect their governance structure and performance. This study investigates the governance mechanisms of publicly funded R&D consortia and their effects on innovation performance. Few studies have empirically addressed the effect of project monitoring by the government or the role of project leadership in R&D consortia. Focusing on a major support program for R&D consortia in Japan and using a sample of 251 firms that participated in publicly funded R&D consortia from 2004 to 2009, we empirically confirm that to enhance firms’ innovation performance, both project leadership as internal discipline and government monitoring as external discipline matter. Our results show that project leadership directly improves firms’ innovation performance, while firms’ commitment indirectly affects performance. Project leadership and government monitoring also promote commitment. Furthermore, both factors are complementary: consortia members are more willing to accept a project leader’s coordination under stricter government monitoring.     

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.     

Impact phase kinematics of instep kicking in soccer

Abstract

The purpose of this study was to capture the lower limb kinematics before during and after ball impact of soccer kicking by examining the influence of both sampling rate and smoothing procedures. Nine male soccer players performed maximal instep kicks and the three-dimensional leg movements were captured at 1000 Hz. Angular and linear velocities and accelerations were determined using four different processing approaches: processed using a modified version of a time-frequency filtering algorithm (WGN), smoothed by a second-order low-pass Butterworth filter at 200 Hz cut-off (BWF), re-sampled at 250 Hz without smoothing (RSR) and re-sampled at 250 Hz but filtered by the same Butterworth filter at 10 Hz cut-off (RSF). The WGN approach appeared to establish representative kinematics, whereas the other procedures failed to remove noisy oscillation from the baseline of signal (BWF), lost the peaks of rapid changes (RSR) or produced totally distorted movement patterns (RSF). The results indicate that the procedures used by some previous studies may have been insufficient to adequately capture the lower limb motion near ball impact. We propose a new time-frequency filtering technique as a better way to smooth data whose frequency content varies dramatically.     

A novel comparison between standard and new testing procedures to assess shock absorbency of third generation artificial turfs

This study aims to re-examine to what extent the testing procedure of the Artificial Athlete Berlin (DIN18032) is a valid evaluation method to assess the shock absorbency of third generation artificial turf (3-g turf) and to establish a new testing procedure, which precisely reflects the acute load by human sports action. The DIN test was conducted for 3-g turfs with different infill component. The baseline of the load of acute human sports action was obtained from the ground reaction force underneath the standard type of 3-g turf sample during landing from a 55-cm height with minimal shock attenuation. For reproducing the force similar to such a hard landing, a testing rig was developed and the same 3-g turf samples were tested. The DIN test failed to distinguish most types of 3-g turf and was found to be inappropriate to evaluate the shock absorbency of the 3-g turf mainly due to bouncing actions of the test foot on measured samples. In contrast, the newly developed testing rig succeeded in illustrating the differences of shock attenuation properties among most types of 3-g turfs in a high loading condition. In terms of players’ safety, the necessity of high loading test using an alternative testing procedure was highlighted.