The influence of golf shaft torque on clubhead kinematics and ball flight     

Sasho James Mackenzie  Erik Matthew Henrikson  Heidi Lynette Macdonald  Troy William Hillier 《Journal of sports sciences》2013,31(24):2849-2855

ABSTRACT

The purpose of this study was to investigate the influence of shaft torque (torsional rigidity) on clubhead kinematics and the resulting flight of the ball. Two driver shafts with disparate levels of torque, but otherwise very similar properties, were tested by 40 right-handed golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. Ball flight and additional clubhead kinematics were collected using a Doppler radar launch monitor. At impact, the high torque shaft (HT) was associated with increased delivered loft (P = .028) and a more open face (P < .001) relative to the low torque shaft (LT). This resulted in the HT shaft being associated with a ball finishing position that was further right (P = .002). At the individual level, the change in face angle due solely to shaft deformation was significantly higher for the HT shaft for 25/40 participants. Although shaft twist was not directly measured, it was logically deduced using the collected data that these outcomes were the result of the HT being twisted more open relative to the LT shaft at impact.  相似文献   

The effect of core training on distal limb performance during ballistic strike manoeuvres     

Benjamin Lee 《Journal of sports sciences》2017,35(18):1768-1780

Ballistic limb motion is enabled by proximal “core” stiffness. However, controversy exists regarding the best method of training this characteristic. This study sought to determine the most effective core training method to enhance distal limb athleticism. A total of 12 participants (24 ± 3 years, 1.8 ± 0.05 m, 76.8 ± 9.7 kg) consisting of Muay Thai athletes performed a core training protocol (Isometric vs. Dynamic, with Control) for 6 weeks, using a repeated measures design to assess performance (peak strike velocity, peak impact force, muscular activation) in various strikes. Isometric training increased impact force in Jab (554.4 ± 70.1 N), Cross (1895.2 ± 203.1 N), Combo (616.8 ± 54.9 N), and Knee (1240.0 ± 89.1 N) trials (P < 0.05). Dynamic training increased strike velocity in Jab (1.3 ± 0.2 m · s^?1), Cross (5.5 ± 0.9 m · s^?1), Combo (0.7 ± 0.1, 2.8 ± 0.3 m · s^?1), and Knee (3.2 ± 0.3 m · s^?1) trials (P < 0.05). Isometric training increased Combo impact force 935.1 ± 100.3 N greater than Dynamic and 931.6 ± 108.5 N more than Control (P < 0.05). Dynamic training increased Jab strike velocity 1.3 ± 0.1 m · s^?1 greater than Isometric and 0.8 ± 0.1 m · s^?1 more than Control (P < 0.05). It appears that both static and dynamic approaches to core training are needed to enhance both velocity and force in distal limbs.  相似文献   

Sprint running: how changes in step frequency affect running mechanics and leg spring behaviour at maximal speed     

Andrea Monte  Valentina Muollo  Francesca Nardello 《Journal of sports sciences》2017,35(4):339-345

The purpose of this study was to investigate the changes in selected biomechanical variables in 80-m maximal sprint runs while imposing changes in step frequency (SF) and to investigate if these adaptations differ based on gender and training level. A total of 40 athletes (10 elite men and 10 women, 10 intermediate men and 10 women) participated in this study; they were requested to perform 5 trials at maximal running speed (RS): at the self-selected frequency (SF_s) and at SF ±15% and ±30%SF_s. Contact time (CT) and flight time (FT) as well as step length (SL) decreased with increasing SF, while k_vert increased with it. At SF_s, k_leg was the lowest (a 20% decrease at ±30%SF_s), while RS was the largest (a 12% decrease at ±30%SF_s). Only small changes (1.5%) in maximal vertical force (F_max) were observed as a function of SF, but maximum leg spring compression (ΔL) was largest at SF_s and decreased by about 25% at ±30%SF_s. Significant differences in F_max, Δy, k_leg and k_vert were observed as a function of skill and gender (P < 0.001). Our results indicate that RS is optimised at SF_s and that, while k_vert follows the changes in SF, k_leg is lowest at SF_s.  相似文献   

The influence of golf shaft stiffness on grip and clubhead kinematics     

Sasho J. MacKenzie  Daniel E. Boucher 《Journal of sports sciences》2017,35(2):105-111

The purpose of this study was to investigate the influence of shaft stiffness on grip and clubhead kinematics. Two driver shafts with disparate levels of stiffness, but very similar inertial properties, were tested by 33 golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. The more flexible shaft (R-Flex) demonstrated a higher contribution to clubhead speed from shaft deflection dynamics (P < .001), but was also associated with significantly less grip angular velocity at impact (P = .001), resulting in no significant difference in clubhead speed (P = .14). However, at the individual level, half of the participants demonstrated a significant difference in clubhead speed between shafts. The more flexible shaft was also associated with significantly different magnitudes of head rotation relative to the grip. More specifically, both bend loft (P < .001) and bend lie (P < .001) were greater for the R-Flex shaft, while bend close (P = .017) was greater for the stiffer (X-Flex) shaft. However, changes in grip orientation resulted in no significant differences in face orientation, between the shafts, at impact.  相似文献   

不同快慢节奏对连续性原地纵跳影响的实验研究   总被引：1，自引：0，他引：1  

单信海 《天津体育学院学报》2007,22(3):228-230

采用录像和测力同步测试的方法，对10名受试者以80、120、160次，min3种不同节奏的连续性原地纵跳动作进行实验测试，结果表明：随着节奏的加快．支撑时间显著缩短；人体腾空的高度、质心下降与上升的最大速度等有显著性的下降；踝、膝、髋3个关节的屈曲程度，膝关节的伸屈角速度都有显著地下降；人体的刚度系数变大，弹性变小。  相似文献   

基于边界摩擦的碟簧隔振器力学性能(英文)     

贾方  张凡成 《东南大学学报》2014,(1):39-44

为研究边界摩擦对碟簧隔振器力学性能的影响,基于能量守恒定律推导了在考虑边界摩擦时碟簧隔振器的载荷位移迟滞曲线公式.通过有限元分析与静载试验验证了该公式的正确性.在此基础上研究了边界摩擦对碟簧隔振器承载能力的影响,并通过动载试验研究了边界摩擦对碟簧隔振器的动态性能的影响.试验结果表明:边界摩擦可提供较大的阻尼,使得碟簧隔振器具有良好的阻尼特性,其阻尼比可达0.23;隔振器的耗能、动刚度和阻尼特性对加载幅值更为敏感,而对加载频率敏感度较小.该研究成果对碟簧隔振器设计具有重要的指导意义.  相似文献   

Loading-unloading test analysis of anisotropic columnar jointed basalts     

Zhi-gang SHAN  Sheng-jie DI 《浙江大学学报(A卷英文版)》2013,14(8):603-614

To evaluate the columnar jointed basalts in the dam site of Baihetan hydropower station in southwest China, we developed a basic conceptual model of single jointed rock mass. Considering that the rock mass deformation consists of rock block deformation and joints deformation, the linear mechanical characteristics of the cell （including the elastic joints and the nonlinear mechanical behaviors of the cell） with a combined frictional-elastic interface were analyzed. We developed formulas to calculate the rock block deformation, which can be adapted for multiple jointed rock mass and columnar jointed basalts. The formulas are effective in calculating the equivalent modulus of multiple jointed rock mass, and precisely reveal the anisotropic properties of columnar jointed basalts. Furthermore, the in situ rigid bearing plate tests were analyzed and calculated, and the types of loading-unloading curves and the equivalent modulus along different directions of columnar jointed basalts were obtained. The analytical results are in close compliance with the test results.  相似文献   

治疗运动员膝关节粘连纤维性僵直41例报告     

张钢林 《山东体育学院学报》1997,(2)

报告了膝关节粘连纤维性僵直41例治疗结果,涉及柔道、摔跤、足球等9项运动。治疗采用我院传统的中医骨伤科疗法,治疗前后膝关节活动范围平均改善76度,最佳者改善130度,效果良好。结合其诊治经验就膝关节粘连纤维性僵直的临床特征与病理改变、治疗方法的选择和治疗特点进行了分析讨论。  相似文献   

Laboratory,computational and field studies of snowboard dynamics     

Buffinton  Keith W.  Shooter  Steven B.  Thorpe  Ira J.  Krywicki  Jason J. 《Sports Engineering》2003,6(3):129-137

  相似文献   

专项武术训练对男性青少年骨骼质量的影响     

孔明涯  林爱翠 《体育科技文献通报》2007,15(12):45-46

为了了解专项武术训练对青少年骨骼质量的影响，采用定量超声骨质成像与测量系统对长期进行专项武术训练的男性青少年进行研究。结论：武术专项的运动员虽然身高、体重较低，但骨密度和骨硬度均显著高于对照组，提示长期有规律地进行武术锻炼有利于提高人体的骨骼质量。  相似文献