首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 734 毫秒
1.
ABSTRACT

The aim of this study was to investigate the kinetic functions of the lower limbs at different hitting-point heights to provide key information for improving batting technique in baseball players. Three-dimensional coordinate data were acquired using a motion capture system (250 Hz) and ground reaction forces were measured using three force platforms (1000 Hz) in 22 male collegiate baseball players during tee-batting set at three different hitting-point heights (high, middle, and low). Kinetic data were used to calculate joint torque and mechanical work in the lower limbs by the inverse dynamics approach. The peak angular velocity of the lower trunk about the vertical axis was smaller under the low condition. The joint torques and mechanical works done by both hip adduction/abduction axes were different among the three conditions. These results indicate that hip adduction/abduction torques mainly contribute to a change in the rotational movement of the lower body about the vertical axis when adjusting for different hitting-point heights. In order to adjust for the low hitting-point height which would be difficult compared with other hitting-point heights, batters should focus on rotating the lower trunk slowly by increasing both hip abduction torques.  相似文献   

2.
The purpose of this study was to investigate the effect of lumbosacral kinetics on sprinting. Twelve male sprinters performed 50 m sprints at maximal effort. Kinematic and ground reaction force data were recorded at approximately 40 m from sprint commencement. A whole-body inverse dynamics approach was applied to calculate joint forces and torques at the hip and lumbosacral joints. The contribution of the hips and lumbosacral joint torques to pelvic rotation was subsequently calculated, with joint force powers indicating the rate of mechanical energy transfer between segments across joint centres calculated for both hip joints. The kinetic analysis indicated that the lumbosacral torsional torque contributed significantly to pelvic rotation. Additionally, the pelvic rotation exerted anterior–posterior joint forces on the hips, contributing to the large positive joint force power at the hip of the stance leg. These hip joint force powers assisted in motion recovery during sprinting. In conclusion, the lumbosacral torsional torque might contribute to the recovery motion in sprinting through application of the anterior–posterior joint forces at the hip joints via pelvic rotation.  相似文献   

3.
Abstract

We aimed to illustrate support leg dynamics during instep kicking to evaluate the role of the support leg action in performance. Twelve male soccer players performed maximal instep kicks. Their motions and ground reaction forces were recorded by a motion capture system and a force platform. Moments and angular velocities of the support leg and pelvis were computed using inverse dynamics. In most joints of the support leg, the moments were not associated with or counteracting the joint motions except for the knee joint. It can be interpreted that the initial knee flexion motion counteracting the extension joint moment has a role to attenuate the shock of landing and the following knee extension motion associated with the extension joint moment indirectly contributes to accelerate the swing of kicking leg. Also, appreciable horizontal rotation of the pelvis coincided with increase of the interaction moment due to the hip joint reaction force on the support leg side. It can be assumed that the interaction moment was the main factor causing the pelvis counter-clockwise rotation within the horizontal plane from the overhead view that precedes a proximal-to-distal sequence of segmental action of the swing leg.  相似文献   

4.
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.  相似文献   

5.
Propulsion and bracing ground reaction force (GRF) in overhand throwing are integral in propagating joint reaction kinetics and ball velocity, yet how stride length effects drive (hind) and stride (lead) leg GRF profiles remain unknown. Using a randomised crossover design, 19 pitchers (15 collegiate and 4 high school) were assigned to throw 2 simulated 80-pitch games at ±25% of their desired stride length. An integrated motion capture system with two force plates and radar gun tracked each throw. Vertical and anterior–posterior GRF was normalised then impulse was derived. Paired t-tests identified whether differences between conditions were significant. Late in single leg support, peak propulsion GRF was statistically greater for the drive leg with increased stride. Stride leg peak vertical GRF in braking occurred before acceleration with longer strides, but near ball release with shorter strides. Greater posterior shear GRF involving both legs demonstrated increased braking with longer strides. Conversely, decreased drive leg propulsion reduced both legs’ braking effects with shorter strides. Results suggest an interconnection between normalised stride length and GRF application in propulsion and bracing. This work has shown stride length to be an important kinematic factor affecting the magnitude and timing of external forces acting upon the body.  相似文献   

6.
Twenty-five volleyball players (14 males, 11 females) were videotaped (60Hz) performing countermovement vertical jumps with and without an arm swing. Ground reaction force and video-based coordinate data were collected simultaneously. The resultant joint force and torque at the hip, knee, ankle and shoulder for two trials per subject per condition were computed and normalized. Average kinematic, resultant joint force and torque data were compared using repeated-measures analysis of variance. Larger values were recorded for the vertical velocity of the centre of mass at take-off in the jumps with (mean 2.75, s=0.3m.s-1) versus without (mean 2.44, s= 0.23m.s-1) an arm swing. The jumps with no arm swing produced larger torques at the hip during the first third of the propulsive phase (from zero to maximum vertical velocity of the centre of mass). During the final two-thirds of the propulsive phase, the arm swing augmented hip extensor torques by slowing the rate of trunk extension and placing the hip extensor muscles in slower concentric conditions that favoured the generation of larger forces and resultant joint torques. During the first two-thirds ofthe propulsive phase, knee extensor torque increased by 28% in the jumps with an arm swing, but maintained a relatively constant magnitude in the jumps with no arm swing.  相似文献   

7.
Twenty-five volleyball players (14 males, 11 females) were videotaped (60 Hz) performing countermovement vertical jumps with and without an arm swing. Ground reaction force and video-based coordinate data were collected simultaneously. The resultant joint force and torque at the hip, knee, ankle and shoulder for two trials per subject per condition were computed and normalized. Average kinematic, resultant joint force and torque data were compared using repeated-measures analysis of variance. Larger values were recorded for the vertical velocity of the centre of mass at take-off in the jumps with (mean 2.75, s = 0.3 m.s-1) versus without (mean 2.44, s = 0.23 m.s-1) an arm swing. The jumps with no arm swing produced larger torques at the hip during the first third of the propulsive phase (from zero to maximum vertical velocity of the centre of mass). During the final two-thirds of the propulsive phase, the arm swing augmented hip extensor torques by slowing the rate of trunk extension and placing the hip extensor muscles in slower concentric conditions that favoured the generation of larger forces and resultant joint torques. During the first two-thirds of the propulsive phase, knee extensor torque increased by 28% in the jumps with an arm swing, but maintained a relatively constant magnitude in the jumps with no arm swing.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
Some studies have reported that overarm baseball pitching shows a proximal to distal sequential joint motion including a rapid extension of the elbow. It has been suggested that the rapid elbow extension just before ball release is not due to the action of the elbow extensor muscles, but the underlying mechanisms are not so clear. The purpose of this study was to determine the contributions of each joint muscular- and motion-dependent torques, including the upper trunk and throwing arm joints to generate the rapid elbow extension during baseball pitching. The right handed throwing motions of three baseball pitchers were recorded using five high-speed video cameras and the positional data were calculated using the direct linear transformation method. A throwing arm dynamic model of the upper trunk and throwing arm joints was then used, including 10 degrees of freedom, to calculate the throwing arm joint muscular-, throwing arm and upper trunk joint motion-, gravity-, and external force-dependent components that contribute to the maximum elbow extension angular velocity. The results showed that the rapid elbow extension was primarily due to the upper trunk counterclockwise rotation and shoulder horizontal adduction angular velocity-dependent torques. This study implied that the trunk counterclockwise rotators and shoulder horizontal adductors generate positive torques to maintain the angular velocities of the upper trunk counterclockwise rotation and shoulder horizontal adduction may play a key role in producing the rapid elbow extension.  相似文献   

11.
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 (Fz) 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 Fz forces decreased to .43 BW while left Fz forces rapidly increased to 1.6 BW at contact. The mean decrease in right Fz forces from peak force until contact was 55%, and the ratio of left to right Fz forces; at impact was 3.67:1. Right mediolateral forces (Fx) 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 Fx 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 (Fy) 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.  相似文献   

12.
Back injuries and the fast bowler in cricket   总被引：5，自引：0，他引：5  
Here, I review research that has investigated the aetiology of injuries experienced by adolescent and adult fast bowlers. Mechanical factors play an important role in the aetiology of degenerative processes and injuries to the lumbar spine. This is particularly so in fast bowling, where a player must absorb vertical and horizontal components of the ground reaction force that are approximately five and two times body weight at front-foot and rear-foot impact, respectively. Attenuated forces are transmitted to the spine through the lower limb, while additional forces at the lumbo-sacral junction are caused by trunk hyperextension, lateral flexion and twisting during the delivery stride. Fast bowlers are classified as side-on, front-on or mixed. The mixed action is categorized by the lower body configuration of the front-on action and the upper body configuration of the side-on technique. This upper body configuration is produced by counter-rotation away from the batsman in the transverse plane about the longitudinal axis of the body of a line through the two shoulders. Counter-rotations of 12-40 degrees during a delivery stride have predicted an increased incidence of lumbar spondylolysis, disc abnormality and muscle injury in fast bowlers. During the delivery stride, the mixed bowling action also shows: more lateral flexion and hyperextension of the lumbar spine at front-foot impact, and a greater range of motion of the trunk over the delivery stride when compared with the side-on and front-on techniques. The pars interarticularis of each vertebra is vulnerable to injury if repetitive flexion, rotation and hyperextension are present in the activity. Fast bowlers should reduce shoulder counter-rotation during the delivery stride to reduce the incidence of back injuries. When a player is required to bowl for extended periods irrespective of technique, overuse is also related to an increased incidence of back injuries and must be avoided.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
This study analyzed the joint torque and the mechanical energy flow in the support legs of skilled male race walkers. Twelve race walkers were videotaped using a high-speed camera at a frame rate of 250 Hz set perpendicular to the sagittal plane of motion; their ground reaction forces were measured with two force platforms. A two-dimensional, 14-segment, linked model was used to calculate the kinetics of the support leg joints. In the initial part of the support phase, the mechanical energy flowed into the thigh and shank by the torque of the large hip extensors and knee flexors. In the middle part, the mechanical energy generated by the torque of the large plantar flexors flowed to the foot and from the foot to the shank by the ankle joint force. The mechanical energy flow by the forward joint force of the support hip was significantly related to the walking speed in the final part of the support phase. Our findings suggest that race walkers in the final part of the support phase should exert the torque of the knee extensors and hip flexors to transfer the mechanical energy more effectively to the support thigh and shank.  相似文献   

16.
PurposeTo determine the effect of unanticipated mid-flight medial-lateral external perturbation of the upper or lower trunk on anterior cruciate ligament (ACL) loading variables during jump-landings.MethodsThirty-two participants performed double-leg vertical jump-landings while bilateral kinematics and kinetics were collected under 6 conditions (upper or lower trunk perturbation locations; no, left, or right perturbation directions). Two customized catapult apparatuses were created to apply pushing perturbation to participants near the maximal jump height.ResultsThe ball contacted participants near the center of mass for the lower-trunk conditions and approximately 23 cm above the center of mass for the upper-trunk conditions. Under upper-trunk perturbation, the contralateral leg demonstrated significantly smaller knee flexion angles at initial contact and greater peak knee abduction angles, peak vertical ground reaction forces, peak knee extension moments, and peak knee adduction moments compared to other legs among all conditions. Under lower-trunk perturbation, the contralateral leg showed significantly smaller knee flexion angles at initial contact and increased peak vertical ground reaction forces and peak knee extension moments compared to legs in the no-perturbation conditions.ConclusionMid-flight external trunk pushing perturbation increased ACL loading variables for the leg contralateral to the perturbation. The upper-trunk perturbation resulted in greater changes in ACL loading variables compared to the lower-trunk perturbation, likely due to trunk and ipsilateral leg rotation and more laterally located center of mass relative to the contralateral leg. These findings may help us understand the mechanisms of indirect-contact ACL injuries and develop jump-landing training strategies under mid-flight trunk perturbation to better prevent ACL injury.  相似文献   

17.
Abstract

The knee is a common site of injury in netball players. In this study, 10 high-performance netball players underwent a biomechanical assessment of their single leg landing technique whilst receiving a pass. Three-dimensional video and ground reaction force data were recorded using a motion analysis system. Net internal knee joint moments were calculated using a rigid body analysis and inverse dynamics. The kinematics of the support leg and front-on video footage was used to investigate whether players adhered to guidelines on safe and effective landing strategies. Results indicated that for most players the internal valgus moment was the largest frontal plane knee moment during the landing phase. This may reflect a relatively greater need to resist varus knee excursion or may be related to the kinematics of the hip. For 6 of the 10 players the rapid change to an internal knee valgus moment coincided with hip adduction. Since an increase in the magnitude of the internal valgus moment may increase the compressive forces in the medial compartment of the knee, further work should be undertaken to determine if a neuromuscular training intervention to improve the strength of the hip musculature may be beneficial for these players. A large relative excursion of the knee compared to the hip may indicate that these players had a greater reliance on the more distal segments of the lower extremity for the attenuation of the ground reaction forces. This information may be used to better understand potential knee injury mechanisms in netball players.  相似文献   

18.
Here, I review research that has investigated the aetiology of injuries experienced by adolescent and adult fast bowlers. Mechanical factors play an important role in the aetiology of degenerative processes and injuries to the lumbar spine. This is particularly so in fast bowling, where a player must absorb vertical and horizontal components of the ground reaction force that are approximately five and two times body weight at front-foot and rear-foot impact, respectively. Attenuated forces are transmitted to the spine through the lower limb, while additional foces at the lumbo-sacral junction are caused by trunk hyperextension, lateral flexion and twisting during the delivery stride. Fast bowlers are classified as side-on, front-on or mixed. The mixed action is categorized by the lower body configuration of the front-on action and the upper body configuration of the side-on technique. This upper body configuration is produced by counter-rotation away from the batsman in the transverse plane about the longitudinal axis of the body of a line through the two shoulders. Counter-rotations of 12–40° during a delivery stride have predicted an increased incidence of lumbar spondylolysis, disc abnormality and muscle injury in fast bowlers. During the delivery stride, the mixed bowling action also shows: more lateral flexion and hyperextension of the lumbar spine at front-foot impact, and a greater range of motion of the trunk over the delivery stride when compared with the side-on and front-on techniques. The pars interarticularis of each vertebra is vulnerable to injury if repetitive flexion, rotation and hyperextension are present in the activity. Fast bowlers should reduce shoulder counter-rotation during the delivery stride to reduce the incidence of back injuries. When a player is required to bowl for extended periods irrespective of technique, overuse is also related to an increased incidence of back injuries and must be avoided.  相似文献   

19.
The aim of the present study was to compare kinetically the roles of the lower extremities in generating trunk rotation in the tennis one-handed and two-handed backhand strokes. Fourteen male collegiate tennis players, seven with a preference for the one- and seven with a preference for the two-handed technique, were recruited as participants. The motion of each backhand stroke was filmed using two high-speed cine-cameras, and the ground reaction forces on the feet were measured separately using two force platforms to determine the joint moments and joint reaction forces at the hip, knee and ankle joints. A significant difference in hip joint moments between the two types of stroke was found in the phase from the start of forward rotation of the pelvis to the start of racket forward movement. For trunk rotation, the one-handed backhand players exerted a large joint moment in the front leg, whereas the two-handed backhand players exerted a large joint moment in the back leg. The exertion of a large hip joint moment in the latter stroke was comparable with the exertion in a forehand stroke reported previously.  相似文献   

20.
The aim of the present study was to compare kinetically the roles of the lower extremities in generating trunk rotation in the tennis one-handed and two-handed backhand strokes. Fourteen male collegiate tennis players, seven with a preference for the one- and seven with a preference for the two-handed technique, were recruited as participants. The motion of each backhand stroke was filmed using two high-speed cine-cameras, and the ground reaction forces on the feet were measured separately using two force platforms to determine the joint moments and joint reaction forces at the hip, knee and ankle joints. A significant difference in hip joint moments between the two types of stroke was found in the phase from the start of forward rotation of the pelvis to the start of racket forward movement. For trunk rotation, the one-handed backhand players exerted a large joint moment in the front leg, whereas the two-handed backhand players exerted a large joint moment in the back leg. The exertion of a large hip joint moment in the latter stroke was comparable with the exertion in a forehand stroke reported previously.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号