A three-dimensional forward dynamics model of the golf swing

Previously, forward dynamic models of the golf swing have been planar, two-dimensional (2D) representations. Research on live golfers has consistently demonstrated that the downswing is not planar. This paper introduces and evaluates the validity of a 3D six-segment forward dynamics model of a golfer. The model incorporates a flexible club shaft and a variable swing plane. A genetic algorithm was developed to optimise the coordination of the model’s mathematically represented muscles (torque generators) in order to maximise clubhead speed at impact. The kinematic and kinetic results confirmed previous findings on the proximal to distal sequencing of joints and the muscles powering those joints. The validity of the mathematical model was supported through comparisons of the model’s swing kinematics and kinetics with those of a live golfer.     

Assessment of planarity of the golf swing based on the functional swing plane of the clubhead and motion planes of the body points

The purposes of this study were (1) to determine the functional swing plane (FSP) of the clubhead and the motion planes (MPs) of the shoulder/arm points and (2) to assess planarity of the golf swing based on the FSP and the MPs. The swing motions of 14 male skilled golfers (mean handicap = -0.5 +/- 2.0) using three different clubs (driver, 5-iron, and pitching wedge) were captured by an optical motion capture system (250Hz). The FSP and MPs along with their slope/relative inclination and direction/direction of inclination were obtained using a new trajectory-plane fitting method. The slope and direction of the FSP revealed a significant club effect (p < 0.001). The relative inclination and direction of inclination of the MP showed significant point (p < 0.001) and club (p < 0.001) effects and interaction (p < 0.001). Maximum deviations of the points from the FSP revealed a significant point effect (p < 0.001) and point-club interaction (p < 0.001). It was concluded that skilled golfers exhibited well-defined and consistent FSP and MPs, and the shoulder/arm points moved on vastly different MPs and exhibited large deviations from the FSP. Skilled golfers in general exhibited semi-planar downswings with two distinct phases: a transition phase and a planar execution phase.     

The relationship between the golf swing plane and ball impact characteristics using trajectory ellipse fitting

The trajectory of the clubhead close to ball impact during the golf swing has previously been shown to be planar. However, the relationship between the plane orientation and the orientation characteristics of the clubhead at ball impact has yet to be defined. Fifty-two male golfers (27 high skilled, 25 intermediate skilled) hit 40 drives each in an indoor biomechanics laboratory. This study successfully fitted the trajectory of the clubhead near impact to an ellipse for each swing for players of different skill levels to help better explain this relationship. Additionally, the eccentricities of the ellipses were investigated for links to skill level. The trajectory of the clubhead was found to fit to an ellipse with RMSE of 1.2 mm. The eccentricity of the ellipse was found to be greater in the high-skilled golfers. The club path and angle of attack generated from the ellipse fitted clubhead trajectory were found to have a normalised bias-corrected RMSE of 2% and 3%, respectively. A set of “rule of thumb” values for the relationship between the club path, angle of attack and delivery plane angle was generated for use by coaches.     

How to quantify the transition phase during golf swing performance: Torsional load affects low back complaints during the transition phase

The transition phase of a golf swing is considered to be a decisive instant required for a powerful swing. However, at the same time, the low back torsional loads during this phase can have a considerable effect on golf-related low back pain (LBP). Previous efforts to quantify the transition phase were hampered by problems with accuracy due to methodological limitations. In this study, vector-coding technique (VCT) method was proposed as a comprehensive methodology to quantify the precise transition phase and examine low back torsional load. Towards this end, transition phases were assessed using three different methods (VCT, lead hand speed and X-factor stretch) and compared; then, low back torsional load during the transition phase was examined. As a result, the importance of accurate transition phase quantification has been documented. The largest torsional loads were observed in healthy professional golfers (10.23 ± 1.69 N · kg^?1), followed by professional golfers with a history of LBP (7.93 ± 1.79 N · kg^?1), healthy amateur golfers (1.79 ± 1.05 N · kg^?1) and amateur golfers with a history of LBP (0.99 ± 0.87 N · kg^?1), which order was equal to that of the transition phase magnitudes of each group. These results indicate the relationship between the transition phase and LBP history and the dependency of the torsional load magnitude on the transition phase.     

Segment coupling and coordination variability analyses of the roundhouse kick in taekwondo relative to the initial stance position

The initial stance position (ISP) has been observed as a factor affecting the execution technique during taekwondo kicks. In the present study, authors aimed to analyse a roundhouse kick to the chest by measuring movement coordination and the variability of coordination and comparing this across the different ISP (0°, 45° and 90°). Eight experienced taekwondo athletes performed consecutive kicking trials in random order from every of the three relative positions. The execution was divided into three phases (stance, first swing and second swing phase). A motion capture system was used to measure athletes’ angular displacement of pelvis and thigh. A modified vector coding technique was used to quantify the coordination of the segments which contributed to the overall movement. The variability of this coordination (CV) for each ISP was also calculated. Comparative analysis showed that during the stance phase in the transverse plane, athletes coordinated movement of the trunk and thigh with a higher frequency of in-phase and lower frequency of exclusive thigh rotation in the 0° stance than the 90° stance position (P < 0.05). CV was also influenced by the different ISP. During the first swing and the majority of the second swing phase, predominant in-phase coordination of the pelvis and thigh was observed. Including exercises that require in-phase movement could not only help athletes to acquire coordination stability but also efficiency. The existence of a constraint such as ISP implies an increase of the variability when the athletes have to kick from ISP they are not used to adopt (i.e., 0° and 90° ISP) as an evidence of adaptability in the athletes’ execution technique.     

Examination of the neuromechanical factors contributing to golf swing performance

This study investigated the relationship between a range of neuromechanical variables in the lower- and upper-body, and golf performance. Participants were assessed for individual muscle stiffness, vertical stiffness (Kvert), flexibility, power and maximal isometric strength. Furthermore, golf performance was determined by handicap and club head speed. Pearson’s correlations quantified the relationships between neuromechanical variables and performance measures. Participants were also separated into relatively high club head speed (HC) and low club head speed (LC) groups and compared for physical characteristics. Club head speed showed positive relationships with Kvert and power and a negative relationship with hip mobility. The HC group exhibited superior Kvert and power, while strength and flexibility measures were not related to performance. Higher levels of lower-body stiffness, rate of force development and power output appear to be beneficial for generating superior club head speed. A stiffer system may reduce the time needed to remove the “slack” from the series elastic component therefore, reducing electromechanical delay and enhancing rate of force development. The large positive association with rate of force development suggests that increasing this component, along with power production may be superior focal components for training in golfers due to the short duration of the downswing.     

双杠支撑摆动“钟摆式”保护方法探讨

运用常规保护法与“钟摆式”保护法等两种不同的方法，对双杠支撑摆动技术进行了研究和实践探索。实践表明：双杠支撑摆动的教学，教练员运用双手同时扶持运动员的躯干定点部位进行保护的方法(“钟摆式”保护法)，有助于运动员在短时间内掌握并提高双杠支撑摆动的技术。     

不同技术类型背越式跳高摆动动作对起跳效果的影响

通过采用不同研究模型对我国优秀男子不同技术类型背越式跳高运动员在起跳时摆动动作效果进行定量分析，探讨我国优秀男子不同技术类型背越式跳高运动员摆动动作对起跳效果的影响。结果表明：我国优秀男子背越式跳高运动员摆动效果约占50％，且摆动效果的大小与技术类型无关，与高度的增加没有线性相关。但当高度增加到本人最好成绩时，摆动作用达到最大值。选用中国男性青年模型与扎齐奥尔斯基模型对背越式跳高技术进行研究，结果没有显差异性。     

浙江省经营性健身俱乐部消费者阶层分析

采用文献资料法和问卷调查等方法,对杭州、宁波、温州经营性健身俱乐部的消费者进行了调研,主要是从健身消费者的年龄、职业、文化程度、收入水平、动机、体育消费水平等几个因素来分析消费者的阶层特点;调查表明消费者阶层特点明显,主要集中在中等收入或高收入人群,这些人收入稳定,薪金丰厚,是健身市场的支柱消费群体.     

Interpersonal dynamics and relative positioning to scoring target of performers in 1 vs. 1 sub-phases of team sports

Abstract

In this study, we examined the effects of relative positioning of attacker–defender dyads to the basket on interpersonal coordination tendencies in basketball. To achieve this aim, four right-hand dominant basketball players performed in a 1 vs. 1 sub-phase, at nine different playing locations relative to the basket (from 0° to 180°, in 20° increments). Performers’ movement displacement trajectories were video-recorded and digitized in 162 trials. Results showed that interpersonal coordination tendencies changed according to the scaling of the relative position of performers to the basket.

Stable in-phase modes of coordination were observed between performers’ longitudinal and lateral displacements (50.47% and 43.02%) on the left side of the court. On the right side of the court, a shift in the dominant mode of coordination was observed to a defender lead-lag of ?30°, both for longitudinal and lateral displacements (30.51% and 32.65%). These results suggest how information about dribbler hand dominance and relative position to the basket may have constrained attacker–defender coordination tendencies in 1 vs. 1 sub-phases of basketball.     

Interpersonal dynamics and relative positioning to scoring target of performers in 1 vs. 1 sub-phases of team sports

Abstract In this study, we examined the effects of relative positioning of attacker-defender dyads to the basket on interpersonal coordination tendencies in basketball. To achieve this aim, four right-hand dominant basketball players performed in a 1 vs. 1 sub-phase, at nine different playing locations relative to the basket (from 0° to 180°, in 20° increments). Performers' movement displacement trajectories were video-recorded and digitized in 162 trials. Results showed that interpersonal coordination tendencies changed according to the scaling of the relative position of performers to the basket. Stable in-phase modes of coordination were observed between performers' longitudinal and lateral displacements (50.47% and 43.02%) on the left side of the court. On the right side of the court, a shift in the dominant mode of coordination was observed to a defender lead-lag of -30°, both for longitudinal and lateral displacements (30.51% and 32.65%). These results suggest how information about dribbler hand dominance and relative position to the basket may have constrained attacker-defender coordination tendencies in 1 vs. 1 sub-phases of basketball.     

对足球俱乐部经营现状的分析

运用文献资料法分析了我国足球俱乐部的经营现状，并对产生困境的深层次原因作了分析。研究表明：我国足球俱乐部的经营困境在于运作不规范、风险成本过高、经营业绩欠佳等原因所致。     

社区体育俱乐部辅助管理中小学体育场馆对外开放的可行性研究

为探讨学校体育场馆对外放开的管理工作,在研究学校体育场馆对外开放的安全隐患和社区体育俱乐部学校资源共享模式的基础上,解析了志愿者服务辅助管理学校体育设施对外开放的可行性。研究表明：社区体育俱乐部志愿者辅助管理学校体育场馆对外开放有利于保障学生的安全、减轻学校的经济负担、保护包括学校体育场地在内的学校财产。     

西藏高校足球俱乐部现状与对策——以西藏民族学院为例

足球运动在西藏民族学院有着广泛的基础,少数民族大学生们非常热衷参与足球俱乐部的活动.但足球俱乐部在建立运行的过程中也暴露了诸多问题.通过调查、走访提出如何解决这些问题的建议,以期促进足球俱乐部的长远健康发展,为大学生们提供锻炼能力的舞台,增强学生体质,丰富课余生活起到积极作用.     

高校健美操俱乐部制教学模式的效应分析

通过对高校实施健美操俱乐部制教学模式的研究,探讨如何将体育教育改革的目的、形式、内容和方法融为一体,使学生在知识、能力、素养各方面得到同步、合理的发展,逐步实现由"应试教育"向"素质教育"的转轨.同时对实践效果进程检验,旨在了解在高校体育课中实施俱乐部制的可行性,为真正建立顺应时代发展需求的高校体育课模式提供参考依据.     

The X-Factor: An evaluation of common methods used to analyse major inter-segment kinematics during the golf swing

Abstract

A common biomechanical feature of a golf swing, described in various ways in the literature, is the interaction between the thorax and pelvis, often termed the X-Factor. There is no consistent method used within golf biomechanics literature however to calculate these segment interactions. The purpose of this study was to examine X-factor data calculated using three reported methods in order to determine the similarity or otherwise of the data calculated using each method. A twelve-camera three-dimensional motion capture system was used to capture the driver swings of 19 participants and a subject specific three-dimensional biomechanical model was created with the position and orientation of each model estimated using a global optimisation algorithm. Comparison of the X-Factor methods showed significant differences for events during the swing (P < 0.05). Data for each kinematic measure were derived as a times series for all three methods and regression analysis of these data showed that whilst one method could be successfully mapped to another, the mappings between methods are subject dependent (P <0.05). Findings suggest that a consistent methodology considering the X-Factor from a joint angle approach is most insightful in describing a golf swing.     

Could knee joint mechanics during the golf swing be contributing to chronic knee injuries in professional golfers?

ABSTRACT

Full three-dimensional movements and external moments in golfers’ knees and the possible involvement in injuries have not been evaluated using motion capture at high sample frequencies. This study measured joint angles and external moments around the three anatomical axes in both knees of 10 professional golfers performing golf drives whilst standing on two force plates in a motion capture laboratory. Significant differences were found in the knee joint moments between the lead and trail limbs for the peak values and throughout all stages during the swing phase. A significantly higher net abduction moment impulse was seen in the trail limb compared with the lead limb (?0.518 vs. ?0.135 Nms.kg^?1), indicating greater loading over the whole swing, which could contribute to knee lateral compartment or anterior cruciate ligament injuries. A significant correlation (r = ?0.85) between clubhead speed at ball contact and maximum joint moment was found, with the largest correlations being found for joint moments at the top of the backswing event and at the end of the follow-through. Therefore, although knee moments can contribute to high clubhead speeds, the large moments and impulses suggest that they may also contribute to chronic knee injuries or exacerbate existing conditions.     

Multi-segment trunk models used to investigate the crunch factor in golf and their relationship with selected swing and launch parameters

The use of multi-segment trunk models to investigate the crunch factor in golf may be warranted. The first aim of the study was to investigate the relationship between the trunk and lower trunk for crunch factor-related variables (trunk lateral bending and trunk axial rotation velocity). The second aim was to determine the level of association between crunch factor-related variables with swing (clubhead velocity) and launch (launch angle). Thirty-five high-level amateur male golfers (Mean ± SD: age = 23.8 ± 2.1 years, registered golfing handicap = 5 ± 1.9) without low back pain had kinematic data collected from their golf swing using a 10-camera motion analysis system operating at 500 Hz. Clubhead velocity and launch angle were collected using a validated real-time launch monitor. A positive relationship was found between the trunk and lower trunk for axial rotation velocity (r(35) = .47, P < .01). Cross-correlation analysis revealed a strong coupling relationship for the crunch factor (R² = 0.98) between the trunk and lower trunk. Using generalised linear model analysis, it was evident that faster clubhead velocities and lower launch angles of the golf ball were related to reduced lateral bending of the lower trunk.     

构建“艺术、体育俱乐部”体系对大学生实施素质教育的实践研究

通过构建"艺术、体育课外俱乐部"来开发校园文化的潜在课程,并探讨通过课外俱乐部形式对实施大学生素质教育的新途径.     

如何确保奥运会世界首要赛事的地位

现代奥运会是在曲折历程中逐步成为国际体育赛事中的首要赛事的.奥运会在举办与管理模式的经验包括:国际奥林匹克大家庭的组建及法律地位的确立;赛事的申办、监控、协调、管理模式的不断完善;奥林匹克思想体系与赛事举办理念的完善与发展;体育活动与相关文化、教育活动体系的丰富和发展;国际奥林匹克运动与国际社会的对话、交流与融合.奥运会保持世界首要赛事地位必须注意几个问题:研究各类国际体育赛事,动态监控其发展的基本态势与特点;进一步完善国际奥林匹克大家庭的管理,建立责权利统一的体系;加强对国际社会文化的干预,丰富奥林匹克思想体系的内涵;建立并统领世界体育赛事的调控机制,尊重各民族和地域性的传统体育;防止商业开发过度,警惕政治干预的负面影响,努力确保奥运会独一无二的国际社会地位.