Ki-Kwang Lee

Effect of Anticipation on Lower Extremity Biomechanics During Side- and Cross-Cutting Maneuvers in Young Soccer Players

Background: Less mature athletes exhibit biomechanical parameters during cutting maneuvers that may place these athletes at greater risk for injury than their more mature counterparts, especially if the maneuvers are unanticipated. However, most studies on risk factors for anterior cruciate ligament (ACL) injury have focused on neuromuscular and knee kinematic differences between the sexes, not on the biomechanical parameters between specific sporting maneuvers. Hypotheses: (1) Anticipation will have a greater effect than the type of cutting maneuver (side- vs cross-cutting) in terms of the biomechanical risk factors for ACL injuries, and (2) the biomechanical risk factors will be different between the 2 types of maneuvers. Study Design: Controlled laboratory study. Methods: Thirty-seven young, male middle school soccer players participated in this study. Three-dimensional motion analysis featuring ground-reaction force and electromyography of the right leg was used. Kinematics, kinetics, and electromyography data for each athlete were analyzed during anticipated and unanticipated side- and cross-cutting maneuvers. The differences between anticipated and unanticipated states as well as between side- and cross-cutting maneuvers were calculated and compared. Results: After unanticipated side-cutting, the time to peak ground-reaction force was longer and peak values were smaller compared with anticipated side-cutting. Flexion, valgus, and internal rotations in the knee joint were larger, and greater flexion and valgus moments were observed. The vastus lateralis and vastus medialis showed lower activity, and the lateral gastrocnemius showed higher activity after unanticipated side-cutting maneuvers. With unanticipated cross-cutting, the time to peak ground-reaction force was longer and peak values were smaller compared with anticipated cross-cutting, and the lateral gastrocnemius showed higher activity. Differences in the peak values of the mediolateral and vertical forces were smaller in the cross-cutting maneuver than in side-cutting. Changes in flexion and adduction of the hip joint, flexion of the knee joint, and inversion of the ankle joint were larger during side-cutting. Conclusion: Although there were some interactions between direction and anticipation, anticipating a cutting maneuver generally had a greater effect than the type of maneuver when there was no significant interaction. Clinical Relevance: Increases in the valgus angle and moment of the knee joint and higher lateral gastrocnemius activity during the late period showed an association with ACL injury risk factors during side-cutting, and higher lateral gastrocnemius activity during the early period showed an association with injury risk factors during cross-cutting.

Shoe collar height effect on athletic performance, ankle joint kinematics and kinetics during unanticipated maximum-effort side-cutting performance

Abstract Side-step cutting manoeuvres comprise the coordination between planting and non-planting legs. Increased shoe collar height is expected to influence ankle biomechanics of both legs and possibly respective cutting performance. This study examined the shoe collar height effect on kinematics and kinetics of planting and non-planting legs during an unanticipated side-step cutting. Fifteen university basketball players performed maximum-effort side-step cutting to the left 45° direction or a straight ahead run in response to a random light signal. Seven successful cutting trials were collected for each condition. Athletic performance, ground reaction force, ankle kinematics and kinetics of both legs were analysed using paired t-tests. Results indicated that high-collar shoes resulted in less ankle inversion and external rotation during initial contact for the planting leg. The high-collar shoes also exhibited a smaller ankle range of motion in the sagittal and transverse planes for both legs, respectively. However, no collar effect was found for ankle moments and performance indicators including cutting performance time, ground contact time, propulsion ground reaction forces and impulses. These findings indicated that high-collar shoes altered ankle positioning and restricted ankle joint freedom movements in both legs, while no negative effect was found for athletic cutting performance.

Indentation on YSZ thermal barrier coating layers deposited by electron beam PVD

We have deposited an yttria-stabilized zirconia (YSZ) layer consisting of microsized grains on an alumina substrate using electron beam physical vapour deposition (EBPVD). The effects of Y2O3 concentration and the coating microstructures of YSZ on indentation damage are investigated. Different coating microstructures are prepared by varying the substrate temperature during deposition. Hertzian and nanoindentation are used to characterize the damage responses of the YSZ thermal barrier-coated alumina layered systems. The damage and failure behaviours have been investigated in relation to the effects of microstructures formed at various substrate temperatures as well as indentation loads from indentation tests. Elastic modulus, hardness, and stress–strain behaviours are characterized by results of the indentation tests. With increasing substrate temperature during the EBPVD process, the overall grain sizes became coarser with a smaller fraction of weak interfaces between the columns, and became more faceted. This change in microstructure ultimately influences the indentation behaviour. The results according to the use of smaller and larger scaled indenters during Hertzian/nanoindentations were also analyzed.

A sensor-aided self coaching model for uncocking improvement in golf swing

This paper describes an autonomous kinematic analysis platform for wrist angle measurement that is capable of evaluating a user’s uncocking motion in his or her golf swing and providing instructional multimodal feedback to improve his or her skills. This uncocking motion, which is a characteristic movement of the wrist during the golf swing, is an important factor in achieving accurate ball hitting and long driving distances, but is difficult to measure. In order to efficiently compute the wrist angle for uncocking evaluation, we present a sensor-based intelligent Inertial Measurement Unit (IMU) agent that collects three-dimensional orientation data during the golf swing from two IMU sensors placed on the forearm and on the golf club. It accurately analyzes changes in wrist angle to detect uncocking throughout the sequence of golf swing motions. In this paper, we first introduce the design considerations based on the concept of the uncocking motion and explain the system architecture with the sensors used for quantitative measurement and qualitative feedback generation. Then, we illustrate the detailed algorithms for wrist angle computation, golf swing motion segmentation based on key pose detection, and uncocking evaluation. A multimodal feedback-based user interface for our system is also presented. Experimental results show that the proposed system has the ability to accurately calculate the wrist angle in real time and also that it can be applied to a practical self-coaching system to improve the uncocking motion.

Effect of shoe heel modifications on shock attenuation and joint loading during extreme lunge movement in elite badminton players

In badminton, lunging is essential and frequently, it accounts for approximately 15% of all badminton movements in competitive single game (Kuntze et al. 2010). Players exhibited about 2.5 BW ground reaction force during each lunge (Kuntze et al. 2010) and this would result in a high force load and painful symptoms on the patellar tendon (Fahlstrom et al. 2002, Peers and Lysens 2005, Boesen et al. 2006). In competitive badminton games, players often performed the extreme lunges having more than 40 degrees of the initial shoe-ground angle that may result in greater impact forces and joint loading than normal lunging. Because the location of initial contact between shoe and ground is around heel edge of shoe, particular modification on the heel shape would be plausible to reduce ground reaction forces and knee joint loading. Currently, no scientific guideline is available to show how the heel modifications of badminton shoe influences heel cushioning during lunge.

Does shoe heel design influence ground reaction forces and knee moments during maximum lunges in elite and intermediate badminton players

Background Lunge is one frequently executed movement in badminton and involves a unique sagittal footstrike angle of more than 40 degrees at initial ground contact compared with other manoeuvres. This study examined if the shoe heel curvature design of a badminton shoe would influence shoe-ground kinematics, ground reaction forces, and knee moments during lunge. Methods Eleven elite and fifteen intermediate players performed five left-forward maximum lunge trials with Rounded Heel Shoe (RHS), Flattened Heel Shoe (FHS), and Standard Heel Shoes (SHS). Shoe-ground kinematics, ground reaction forces, and knee moments were measured by using synchronized force platform and motion analysis system. A 2 (Group) x 3 (Shoe) ANOVA with repeated measures was performed to determine the effects of different shoes and different playing levels, as well as the interaction of two factors on all variables. Results Shoe effect indicated that players demonstrated lower maximum vertical loading rate in RHS than the other two shoes (P < 0.05). Group effect revealed that elite players exhibited larger footstrike angle, faster approaching speed, lower peak horizontal force and horizontal loading rates but higher vertical loading rates and larger peak knee flexion and extension moments (P < 0.05). Analysis of Interactions of Group x Shoe for maximum and mean vertical loading rates (P < 0.05) indicated that elite players exhibited lower left maximum and mean vertical loading rates in RHS compared to FHS (P < 0.01), while the intermediate group did not show any Shoe effect on vertical loading rates. Conclusions These findings indicate that shoe heel curvature would play some role in altering ground reaction force impact during badminton lunge. The differences in impact loads and knee moments between elite and intermediate players may be useful in optimizing footwear design and training strategy to minimize the potential risks for impact related injuries in badminton.

Effect of Intentional Draw & Fade Shots on Golf Swing Mechanics

Intentional draw and fade shots could be good weapons for lowering golf score. But how to make such shots? To investigate deterministic variables generating different projectile paths of shots in square stance was the purpose of this study. Ten right-handed male collegiate athletes, showing 1.3 of averaged handicap, participated in this study. They were asked to intentionally perform three different shots such as the straight shot(control condition), draw shot, and fade shot. Swing path, pelvis rotation angle, thorax rotation angle and left forearm supination angle were determined for dependent variables on impact event at each trial. For statistical analysis one-way repeated measures ANOVA were used. The results showed that swing path was one of main factor making differences among three kind of shots. Straight shot vs. Draw shot, Straight shot vs. Fade shot and Draw shot vs. Fade shot showed differences on swing path. And left forearm supination angle revealed significant difference between draw shot and fade shot, showing a significant larger angle of draw shot than fade shot. No other significant difference was detected for the other variables. We found that the shot characteristics were influenced primarily by swing path and left forearm supination angle.

Effects of forefoot bending stiffness of badminton shoes on agility, comfort perception and lower leg kinematics during typical badminton movements

Abstract This study investigated whether an increase in the forefoot bending stiffness of a badminton shoe would positively affect agility, comfort and biomechanical variables during badminton-specific movements. Three shoe conditions with identical shoe upper and sole designs with different bending stiffness (Flexible, Regular and Stiff) were used. Elite male badminton players completed an agility test on a standard badminton court involving consecutive lunges in six directions, a comfort test performed by a pair of participants conducting a game-like practice trial and a biomechanics test involving a random assignment of consecutive right forward lunges. No significant differences were found in agility time and biomechanical variables among the three shoes. The players wearing the shoe with a flexible forefoot outsole demonstrated a decreased perception of comfort in the forefoot cushion compared to regular and stiffer conditions during the comfort test (p < 0.05). The results suggested that the modification of forefoot bending stiffness would influence individual perception of comfort but would not influence performance and lower extremity kinematics during the tested badminton-specific tasks. It was concluded that an optimisation of forefoot structure and materials in badminton shoes should consider the individual’s perception to maximise footwear comfort in performance.

Evaluation of the interaction between contact force and decision making on lower extremity biomechanics during a side-cutting maneuver

IntroductionThe purposes of this study were (1) to compare the effect between contact force [first and second ground reaction force (GRF)] and decision making (anticipation vs unanticipation) on lower extremity biomechanics during a side-cutting maneuver in young soccer players; and (2) to identify which condition is more vulnerable to biomechanical risk factors of the anterior cruciate ligament (ACL) injury.Materials and methodsSixteen young, male middle school soccer players with right leg dominance participated in this study. Three-dimensional motion analysis featuring GRF and electromyography (EMG) of the right leg was used during the stance phase of the side-cutting maneuver. Kinematics, kinetics, and EMG data for each athlete were analyzed and averaged for three successful anticipated and unanticipated side-cutting maneuvers.ResultsGRF was smaller and muscle activities were lower in most muscle groups in the first peak than that of the second peak. More flexion and internal rotational angles of the hip joint were observed in the unanticipated first peak that that of the second peak. Lesser flexion angle and moment of the knee joint observed in the first peak than that of the second peak, and abduction moment was increased after the unanticipation.ConclusionThe GRF and muscle activities were smaller in the first peak than those in the second peak; however, first peak showed a closer association with biomechanical risk factors of the ACL injury. There were some interactions between contact force and decision making and unanticipation made the first peak more risky to the ACL injury.

Effect of shoe heel to toe drop and strike patterns in sole angle

In recent years, minimalist running shoes have seen a rapid boom in popularity especially in the running market worldwide. Some arguments have been made about the different strike patterns. Conventional running shoes are designed with a thick heel stack height but minimalist running shoes have a lower heel stack height. Some footwear companies insist that minimalist running shoes strengthen the feet, are safer, improve proprioceptive sensors, and allow a more natural movement. Some shoe companies insist that minimalist running shoes lead to a forefoot strike or midfoot strike during running and so deem that they are safer for running. Strike pattern differences in running have been studied extensively during recent years (Daniel et al. 2009, Daniel et al. 2012). However, there has been minimal research regarding heel-toe drop.