Athletics

The purposes of this study were to investigate (1) the relationships between official distance and selected ground reaction measures during discus throwing; and (2) the relationships between selected ground reactions and selected lower extremity joint kinetics. Three high‐speed video cameras and three force plates were used to collect three‐dimensional videographic and force plate data in this study. An inverse dynamic model was used to determine the lower extremity kinetics. Multiple regression analyses were conducted to determine relationships of the selected kinematic and kinetic measures with the official distance. Official distance was significantly correlated with ground reaction forces on the left foot during the first single‐support phase, on the right foot during the second single‐support phase and delivery phase, and on the left foot during the delivery phase. Also, the right‐hip extension and internal rotation moments and left‐knee extension moment during the delivery phase were significantly correlated with official distance. These results suggest that discus throwers should drive vigorously forward during the first single‐support phase and increase the landing impact force on the right foot after flight. Also they should increase forward and rightward ground reaction force on the right foot and backward and vertical force on the left foot by powerful right‐hip extension and internal rotation and left‐knee extension during the delivery phase. These results provide critical information regarding the training of discus‐throwing techniques, and the direction of future biomechanical studies on this event.     

我国优秀女子铁饼运动员旋转节奏—结构特征的研究

通过运动学分析方法,对2008年北京奥运会我国5名达到A标运动员的投掷技术分析发现,孙太凤预摆和起转技术以及双脚的站位有很大问题;宋爱民有腾空时间短、旋转过程中重心和铁饼速度增加过快、右腿摆动弧线小、右脚着地过快等缺点;马雪君的右腿摆动弧线大,右脚抬得过高,增大了摆动半径,延长了左脚在地面停留的时间;徐邵阳有旋转阶段身体重心腾空过高、腾空时间长、着地不积极等缺点.     

The Mechanics of Batting: Analysis of Ground Reaction Forces and Selected Lower Extremity Kinematics

Abstract

The purpose of this study was to examine variations in ground reaction forces and selected lower extremity kinematics during the stride and swing phases of batting. High speed photography (100 fps) employing direct linear transformation methodology and a force plate were used to record three-dimensional kinematic and kinetic data for 7 female fast pitch softball batters. Mean vertical forces (F_z) of the right or rear foot increased to approximately 1 BW during the stride. Once the left or forward foot made contact with the ground after completion of the stride, right F_z forces decreased to .43 BW while left F_z forces rapidly increased to 1.6 BW at contact. The mean decrease in right F_z forces from peak force until contact was 55%, and the ratio of left to right F_z forces; at impact was 3.67:1. Right mediolateral forces (F_x) were exerted laterally, away from the batter, and were responsible for initiating movement of the body toward the pitched ball. As the left foot made contact with the ground at completion of the stride, left F_x forces were exerted laterally toward the pitched ball. The reaction to these forces retarded the batter's forward momentum, increased stability, and caused the left hip and knee to extend as contact approached. Right and left anteroposterior forces (F_y) acted in opposite directions (right foot pushing backward, left foot pushing forward), and were responsible for rotating the hips and upper body in a counterclockwise direction toward the pitched ball. Horizontal angular deceleration of both thighs just prior to contact was due, in part, to a decrease in these forces. These data may prove helpful when attempting to identify atypical batting patterns, and when considering improvements in shoe design. In the latter instance, force production and stability may be enhanced by aligning the cleats along the lines of action of the applied resultant shear forces.     

The influence of foot position on scrum kinetics during machine scrummaging

ABSTRACT

The purpose of this study was to investigate the effect of variations in the alignment of the feet on scrum kinetics during machine scrummaging. Twenty nine rugby forwards from amateur-level teams completed maximal scrum efforts against an instrumented scrum machine, with the feet in parallel and non-parallel positions. Three-dimensional forces, the moment about the vertical axis and sagittal plane joint angles were measured during the sustained pushing phase. There was a decrease in the magnitude of the resultant force and compression force in both of the non-parallel conditions compared to parallel and larger compression forces were associated with more extended hip and knee angles. Scrummaging with the left foot forward resulted in the lateral force being directed more towards the left and the turning moment becoming more clockwise. These directional changes were reversed when scrummaging with the right foot forward. Scrummaging with the right foot positioned ahead of the left may serve to counteract the natural clockwise wheel of the live scrum and could be used to achieve an anti-clockwise rotation of the scrum for tactical reasons. However, this would be associated with lower resultant forces and a greater lateral shear force component directed towards the right.     

Comparison of crossover and jab step start techniques for base stealing in baseball

Base stealing is an important tactic for increasing the chance of scoring in baseball. This study aimed to compare the crossover step (CS) and jab step (JS) starts for base stealing start performance and to clarify the differences between CS and JS starts in terms of three-dimensional lower extremity joint kinetics. Twelve male baseball players performed CS and JS starts, during which their motion and the force they applied to the ground were simultaneously recorded using a motion-capture system and two force platforms. The results showed that the normalised average forward external power, the average forward–backward force exerted by the left leg, and the forward velocities of the whole body centre of gravity generated by both legs and the left leg were significantly higher for the JS start than for the CS start. Moreover, the positive work done by hip extension during the left leg push-off was two-times greater for the JS start than the CS start. In conclusion, this study has demonstrated that the jab step start may be the better technique for a base stealing start and that greater positive work produced by left hip extension is probably responsible for producing its larger forward ground reaction force.     

The influence of cricket fast bowlers’ front leg technique on peak ground reaction forces

Abstract

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.     

Ground reaction force measures when running in soccer boots and soccer training shoes on a natural turf surface

There are differences in ground reaction force when wearing soccer boots compared with training shoes on a natural turf surface. Two natural-turf-covered force platforms, located outdoors in a field, allowed comparison of performance when six-studded soccer boots and soccer training shoes were worn during straight fast running (5.4 m s^-1 ± 0.27 m s-1) and slow running (4.4 m^s-1 ± 0.22 m s^-1). Six male soccer players (mean age: 25 ± 4.18 years; mean mass 79.7 ±9.32 kg) struck the first platform with the right foot and the second platform with the left foot. In fast running, the mean vertical impact peak was significantly greater in soccer boots (2.706 BW) than in training shoes (2.496 BW) when both the right and left foot were considered together and averaged (P = 0.003). Similarly, the mean vertical impact peak loading rate was greater when wearing soccer boots at 26.09 BWs^-1 compared to training shoes (21.32 BWs^-1;P = 0.002). Notably, the mean vertical impact peak loading rate of the left foot (boots: 28.07 BWs^-1; shoes: 22.52 BWs^-1) was significantly greater than the right foot (boots: 24.11 BWs^-1; shoes: 20.11 BWs^-1) in both boots and shoes (P = 0.018). The braking force was greater for the left foot (P = 0.013). In contrast, mean peak vertical propulsion forces were greater for the right foot (P > 0.001) when either soccer boots or training shoes were considered. Similar significant trends were evident in slow running, and, notably, in both soccer boots and training shoes medial forces were greater for the left foot (P = 0.008) and lateral forces greater for the right foot (P = 0.011). This study showed the natural turf ground reaction force measurement system can highlight differences in footwear in an ecological environment. Greater forces and impact loading rates occurred during running activity in soccer boots than in training shoes, with soccer boots showing reduced shock attenuation at impact. Such findings may have implications for impact-related injuries with sustained exposure, especially on harder natural-turf surfaces. There were differences in the forces occurring at the right and left feet with the ground, thus suggesting the use of bipedal monitoring of ground reaction forces.     

我国优秀女子铁饼运动员宋爱民投掷铁饼技术的三维运动学分析

宋爱民是我国优秀的女子铁饼运动员之一,她的技术风格代表了我国优秀的女子铁饼运动员的技术特征,发挥了我国优秀女子铁饼运动员身材灵巧的特点。运用三维摄像法对宋爱民的完整技术进行分析,得出相关数据,并与国外优秀运动员进行对比分析。研究结果表明:在右脚着地到左脚着地阶段,宋爱民的技术特点表现出非常快的特点,投掷臂在旋转过程中不太稳定,造成了一部分速度的损失。     

Lower extremity kinematics of athletics curve sprinting

Curve running requires the generation of centripetal force altering the movement pattern in comparison to the straight path run. The question arises which kinematic modulations emerge while bend sprinting at high velocities. It has been suggested that during curve sprints the legs fulfil different functions. A three-dimensional motion analysis (16 high-speed cameras) was conducted to compare the segmental kinematics of the lower extremity during the stance phases of linear and curve sprints (radius: 36.5 m) of six sprinters of national competitive level. Peak joint angles substantially differed in the frontal and transversal plane whereas sagittal plane kinematics remained unchanged. During the prolonged left stance phase (left: 107.5 ms, right: 95.7 ms, straight: 104.4 ms) the maximum values of ankle eversion (left: 12.7°, right: 2.6°, straight: 6.6°), hip adduction (left: 13.8°, right: 5.5°, straight: 8.8°) and hip external rotation (left: 21.6°, right: 12.9°, straight: 16.7°) were significantly higher. The inside leg seemed to stabilise the movement in the frontal plane (eversion–adduction strategy) whereas the outside leg provided and controlled the motion in the horizontal plane (rotation strategy). These results extend the principal understanding of the effects of curve sprinting on lower extremity kinematics. This helps to increase the understanding of nonlinear human bipedal locomotion, which in turn might lead to improvements in athletic performance and injury prevention.     

Comparison of three-dimensional lower extremity running kinematics of young adult and elderly runners

The objective of this study was to compare the three-dimensional lower extremity running kinematics of young adult runners and elderly runners. Seventeen elderly adults (age 67-73 years) and 17 young adults (age 26-36 years) ran at 3.1 m x s(-1) on a treadmill while the movements of the lower extremity during the stance phase were recorded at 120 Hz using three-dimensional video. The three-dimensional kinematics of the lower limb segments and of the ankle and knee joints were determined, and selected variables were calculated to describe the movement. Our results suggest that elderly runners have a different movement pattern of the lower extremity from that of young adults during the stance phase of running. Compared with the young adults, the elderly runners had a substantial decrease in stride length (1.97 vs. 2.23 m; P = 0.01), an increase in stride frequency (1.58 vs. 1.37 Hz; P = 0.002), less knee flexion/extension range of motion (26 vs. 33 degrees ; P = 0.002), less tibial internal/external rotation range of motion (9 vs. 12 degrees ; P < 0.001), larger external rotation angle of the foot segment (toe-out angle) at the heel strike (-5.8 vs. -1.0 degrees ; P = 0.009), and greater asynchronies between the ankle and knee movements during running. These results may help to explain why elderly individuals could be more susceptible to running-related injuries.     

Effect of strength on plant foot kinetics and kinematics during a change of direction task

Abstract

Understanding the magnitude of forces and lower body kinematics that occur during a change of direction (COD) task can provide information about the biomechanical demands required to improve performance. To compare the magnitude of force, impulse, lower body kinematics and post-COD stride velocity produced between athletes of different strength levels during a COD task, 12 stronger (8 males, 4 females) and 12 weaker (4 males, 8 females) recreational team sport athletes were recruited. Strength levels were determined by relative peak isometric force of the dominant and non-dominant leg. All athletes performed 10 pre-planned 45° changes of direction (5 left, 5 right) while three-dimensional motion and ground reaction force (GRF) data were collected. Differences in all variables for the dominant leg were examined using a one-way analysis of variance (ANOVA) with a level of significance set at p ≤0.05. The stronger group displayed significantly faster post-COD stride velocity and greater vertical and horizontal braking forces, vertical propulsive force, vertical braking impulse, horizontal propulsive impulse, angle of peak braking force application, hip abduction and knee flexion angle compared to the weaker group. The results suggest that individuals with greater relative lower body strength produced higher magnitude plant foot kinetics and modified lower body positioning while producing faster COD performances. Future investigations should determine if strength training to enable athletes to increase plant foot kinetics while maintaining or adopting a lower body position results in a concomitant increases in post-COD stride velocity.     

Kinetics of throwing arm joints and the trunk motion during an overarm distance throw by skilled Japanese elementary school boys

The purpose of this study was to investigate joint kinetics of the throwing arms and role of trunk motion in skilled elementary school boys during an overarm distance throw. Throwing motions of 42 boys from second, fourth, and sixth grade were videotaped with three high-speed cameras operating at 300 fps. Seven skilled boys from each grade were selected on the basis of throwing distance for three-dimensional kinetic analysis. Joint forces, torques, and torque powers of the throwing arm joints were calculated from reconstructed three-dimensional coordinate data smoothed at cut-off frequencies of 10.5–15 Hz and by the inverse dynamics method. Throwing distance and ball velocity significantly increased with school grade. The angular velocity of elbow extension before ball release increased with school grade, although no significant increase between the grades was observed in peak extension torque of elbow joint. The joint torque power of shoulder internal/external rotation tended to increase with school grade. When teaching the overarm throw, elementary school teachers should observe large backward twisting of trunk during the striding phase and should keep in mind that young children, such as second graders (age 8 years), will be unable to effectively utilise shoulder external/internal rotation during the throwing phase.     

我国女子铁饼优秀运动员过渡和最后用力阶段技术动力学及运动学的特征

时目前我国3名优秀女子铁饼运动员投掷技术进行同步研究发现,宋爱民存在腾空时间短、重心高、右脚着地早、上下肢扭紧差,最后用力阶段重心向投掷方向移动速度快、左右脚在垂直方向和前后方向的力较大、力量的向前行较好;孙太凤缓冲时间较短、右腿蹬伸充分、垂直方向和向前的力量较大;李艳凤过渡阶段上下肢扭紧好、身体后倾角度大、右脚着地对地面冲击力大、左右方向的力较大、力量在左右腿之间移动幅度大、没有转化为向前或者垂直方向的力量,向前性差,蹬伸不充分.     

Comparison of three-dimensional lower extremity running kinematics of young adult and elderly runners

Abstract

The objective of this study was to compare the three-dimensional lower extremity running kinematics of young adult runners and elderly runners. Seventeen elderly adults (age 67–73 years) and 17 young adults (age 26–36 years) ran at 3.1 m · s^?1 on a treadmill while the movements of the lower extremity during the stance phase were recorded at 120 Hz using three-dimensional video. The three-dimensional kinematics of the lower limb segments and of the ankle and knee joints were determined, and selected variables were calculated to describe the movement. Our results suggest that elderly runners have a different movement pattern of the lower extremity from that of young adults during the stance phase of running. Compared with the young adults, the elderly runners had a substantial decrease in stride length (1.97 vs. 2.23 m; P = 0.01), an increase in stride frequency (1.58 vs. 1.37 Hz; P = 0.002), less knee flexion/extension range of motion (26 vs. 33°; P = 0.002), less tibial internal/external rotation range of motion (9 vs. 12°; P < 0.001), larger external rotation angle of the foot segment (toe-out angle) at the heel strike (?5.8 vs. ?1.0°; P = 0.009), and greater asynchronies between the ankle and knee movements during running. These results may help to explain why elderly individuals could be more susceptible to running-related injuries.     

In vivo lumbo-sacral forces and moments during constant speed running at different stride lengths

The aim of this study was to introduce a Newton-Euler inverse dynamics model that included reaction force and moment estimation at the lumbo-sacral (L5-S1) and thoraco-lumbar (T12-L1) joints. Data were collected while participants ran over ground at 3.8 m x s(-1) at three different stride lengths: preferred stride length, 20% greater than preferred, and 20% less than preferred. Inputs to the model were ground reaction forces, bilateral lower extremity and pelvis kinematics and inertial parameters, kinematics of the lumbar spine and thorax and inertial parameters of the lumbar segment. Repeated measures ANOVA were performed on the lower extremity sagittal kinematics and kinetics, including L5-S1 and T12-L1 three-dimensional joint angles, reaction forces and moments at touchdown and peak values during impact phase across the three stride conditions. Results indicated that L5-S1 and T12-L1 vertical reaction forces at touchdown and during the impact portion of the support phase increased significantly as stride length increased (P < 0.001), as did peak sagittal L5-S1 moments during impact (P = 0.018). Additionally, the transverse T12-L1 joint moment increased as running speed increased (P = 0.006). We concluded from our findings that our model was sensitive to our perturbations in healthy runners, and may prove useful in future mechanistic studies of L5-S1 mechanics.     

等速测试条件下摔跤滚桥技术的动力学、运动学及表面肌电特征

采用自主研发的摔跤滚桥测力系统结合定点摄像技术和表面肌电采集技术,对10名男子古典式摔跤一级运动员滚桥技术的动力学、运动学、表面肌电特征进行分析。结果显示:①滚桥技术的力量峰值出现在69°,运动员的滚桥技术峰值扭矩可达自身体质量的(2.11±0.64)倍。②右腹外斜肌和右臀大肌的肌肉激活持续时间最长,分别达5.83 s和5.94 s。③右股直肌、右腹外斜肌、右臀大肌分别在0~90°、0~120°、0~180°范围内做功水平显著高于对侧,左背阔肌在0~30°和120~180°范围内做功水平高于对侧。提示:①在滚桥技术初期,假人滚动的力量主要由双腿蹬伸迅速过渡到右腿侧向蹬伸用力、躯干右旋体位下左旋用力、左臂随躯干左旋方向提拉假人用力构成。②30°后,假人滚动的力量主要由右腿髋、膝关节伸展肌群和躯干左旋肌群收缩用力构成,在约69°时呈现滚桥技术峰值力量体位,此后滚桥力量持续减小。③120°后,假人滚动的力量主要由左肩伸展的拉动假人动作和右髋伸展的挺髋动作用力构成。     

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

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.     

Kinetic analysis of the lower limbs in baseball tee batting

The purpose of this study was to investigate effects of the ground reaction forces on the rotation of the body as a whole and on the joint torques of the lower limbs associated with trunk and pelvic rotation in baseball tee batting. A total of 22 male collegiate baseball players participated in this study. Three-dimensional coordinate data were acquired by a motion capture system (250 Hz), and ground reaction forces of both legs were measured with three force platforms (1,000 Hz). Kinetic data were used to calculate the moment about the vertical axis through the body’s centre of mass resulting from ground reaction forces, as well as to calculate the torque and mechanical work in the lower limb joints. The lateral/medial ground reaction force generated by both legs resulted in the large whole body moment about its vertical axis. The joint torques of flexion/extension of both hips, adduction of the stride hip and extension of the stride knee produced significantly larger mechanical work than did the other joint torques. To obtain high bat-head speed, the batter should push both legs in the lateral/medial direction by utilising both hips and stride knee torques so as to increase the whole body rotation.     

再论推铅球的最后用力

在对推铅球最后用力概念界定的基础上 ,重新划分推铅球最后用力的阶段。查阅了国内外有关的文献资料 ,在此基础上进行数理统计分析 ,提出了划分推铅球最后用力阶段的新理论 :推铅球最后用力阶段是从支撑脚着地后积极蹬伸产生向前水平支撑反力开始到铅球离手的过程。整个最后用力阶段分为单支撑和双支撑 ,单支撑最后用力阶段对左趾向前水平位移、身体重心速度水平向前增量有积极的作用 ,促进左脚积极着地进入双支撑最后用力阶段。在训练中选择提高下肢离心 -向心收缩能力的练习 ,提高力量训练效果。