Three-dimensional kinematic analysis of the snatch of elite Greek weightlifters

We investigated the linear kinematics and the change in energy of the barbell and the angular kinematics of the trunk and leg during the snatch technique of 12 elite male Greek weightlifters under competitive conditions after the new weight classification. Two S-VHS cameras operating at 60 Hz were used to record the lifts. The spatial coordinates of selected points were calculated using the direct linear transformation procedure; after digital filtering of the raw data, the angular displacements and angular velocities were calculated for the hip, knee and ankle joints. The following variables were also calculated for the barbell: vertical and horizontal displacement, vertical linear velocity and acceleration, external mechanical work and power output. The results revealed that all weightlifters flexed their knees during the transition phase, independently of their weight category. This indicates that the athletes use the elastic energy produced during the stretch-shortening cycle to enhance their performance. In nine athletes, we found that the barbell trajectory did not cross a vertical reference line that passed through the initial position of the barbell. The vertical linear velocity of the barbell was increased continuously from the beginning of the movement until the second maximum extension of the knee joint, with no notable dip being observed. Regarding the change in energy of the barbell, we found that the mechanical work for the vertical displacement of the barbell in the first pull was significantly greater than the mechanical work in the second pull. In contrast, the estimated average mechanical power output of the athletes during the vertical displacement of the barbell was significantly greater in the second pull than in the first pull. We conclude that the major elements of the snatch technique of elite Greek weightlifters have not been affected by the new weight classification.     

Biomechanical analysis of the snatch technique in junior elite female weightlifters

The strength and technical competence of junior female lifters play a decisive role not only for their current but also adulthood performance. The objective of this study was to investigate the three-dimensional kinematics of the snatch technique in junior female weightlifters. Ten elite junior female weightlifters participated in the study. Two cameras operating at 50 fields per second were used to record the lifts. The heaviest successful lifts were selected for the kinematic analysis. The kinematical data were obtained using a motion analysis system. The duration of the first pull was significantly longer than that of the other phases (P < 0.05). Maximum extension angle and velocity of the lower limb joints were significantly greater in the second pull (P < 0.05). The greatest extension angle was found in the knee joint during the first pull, while the greatest extension angle was observed in the hip joint during the second pull (P < 0.05). Maximum extension velocity of the knee and hip joints was significantly greater than that of the ankle in both phases (P < 0.05). In addition, the vertical velocity of the barbell and the absolute and relative power outputs was significantly higher in the second pull than in the first pull (P < 0.05). In the snatch lifting of junior female weightlifters, the angular kinematics of lower limb joints, the linear kinematics and trajectory of the barbell and other energy characteristics are similar to and consistent with the values reported in literature for adult female weightlifters.     

An upper limb kinematic model for the examination of cricket bowling: A case study of Mutiah Muralitharan

We show how biomechanics can be used to accurately assess spin-bowling techniques (offspin, legspin and topspin) in cricket, under controlled conditions, when the player is suspected of throwing. A 50 Hz six-camera Vicon Motion Analysis system was used to record the movements of markers strategically placed on the upper limb during each of the above bowling actions. A kinematic model of the upper limb, created using Vicon BodyBuilder® software, enabled the movements of the upper arm and forearm to be described during each delivery. Selected physical characteristics of the upper limb were also measured. The present 'no ball' law in cricket with reference to throwing states that 'the arm should not be straightened in the part of the delivery that immediately precedes ball release'. The bowler, Mutiah Muralitharan, was shown to maintain a relatively constant elbow angle in the 0.06 s before ball release. Furthermore, this angle changed little from the time that the upper arm was angled vertically downward until ball release during the three spin-bowling actions.     

Three-dimensional kinematic analysis and power output of elite flat-water kayakers

The purpose was to examine power output and three-dimensional (3D) kinematic variables in the upper limbs, lower limbs and trunk in elite flat-water kayakers during kayak ergometer paddling. An additional purpose was to analyse possible changes in kinematics with increased intensity and differences between body sides. Six male and four female international level flat-water kayakers participated. Kinematic and kinetic data were collected during three tasks; low (Int_L), high (Int_H) and maximal (Int_M) intensities. No differences were observed in any joint angles between body sides, except for shoulder abduction. Significantly greater range of motion (RoM) values were observed for Int_H compared to Int_L and for Int_M compared to Int_L in trunk and pelvis rotation, and in hip, knee and ankle flexion. The mean maximal power output was 610 ± 65 and 359 ± 33 W for the male and female athletes, respectively. The stroke frequencies were significantly different between all intensities (Int_L 59.3 ± 6.3; Int_H 108.0 ± 6.8; Int_M 141.7 ± 18.4 strokes/min). The results showed that after a certain intensity level, the power output must be increased by other factors than increasing the joint angular RoM. This information may assist coaches and athletes to understand the relationship between the movement of the kayaker and the paddling power output.     

我国优秀男子跳远运动员起跳过程中送髋技术的三维运动学分析

选取近三年来参加全国田径锦标赛8名男子跳远运动员为研究对象,主要采用文献资料法、三维运动录像解析法、数理统计法及逻辑分析法,对跳远起跳技术进行研究。结果表明:送髋技术对跳远成绩有一定影响;我国优秀男子跳远运动员送髋技术有一定缺陷;着板瞬间,起跳腿髋角较小,向上向前送髋不积极;摆动腿髋角较大,摆动腿侧以髋带腿的摆动幅度小、摆动速度慢;缓冲阶段摆动腿一味强调加快摆腿,而忽略了以髋带腿加速前摆;蹬伸阶段,起跳腿侧向前送髋速度慢、幅度小、蹬地不够充分、不能与送髋、蹬地和伸膝的运动方向保持一致,协助身体重心的交换由下到向上向前转移,且摆动腿侧送髋角度小;也有运动员过度的追求髋部前移而忽视垂直向上用力,导致离板瞬间身体重心投影点与身体重心支撑点距离增大。     

山东省优秀男子举重运动员抓举技术动作生物力学分析

根据定性与定量相结合的原则,采用摄像解析及三维测力相结合的方法,对山东省男子举重队6名运动员的抓举动作进行诊断和评价,为其改进技术动作,提高运动成绩提供参考依据.研究结果表明,抓举过程中杠铃中心点运动轨迹应尽可能成垂直直线向上,S型弧度要小,发力后杠铃应达到一定最大速度,部分优秀运动员下蹲时加速度大于自由落体加速度,杠铃上抛中心点与身高的比值应控制在70%左右.抓举过程中人体膝关节角度曲线成双峰,而髋关节角度曲线为单峰,髋关节不可过早打开,躯干也不可过早用力.抓举整个过程环环相扣,每个阶段的发挥对下一阶段均有重要影响,对抓举的技术分析应采用系统的思考方法.     

我国优秀举重运动员专项形态特征与评价标准研究

以我国优秀举重运动员为研究对象,以探寻其专项形态特征、制定评价体系为目的,采用文献资料和数理统计法,对形态各指标进行研究,结果表明:髂宽指数、克托莱指数和体脂百分比最能反映出我国优秀举重运动员的专项形态特征,各指标权重的大小,提示我国优秀举重运动员的专项形态特征是以反应全身肌肉质量(克托莱指数、体脂百分比)为主的,而体型(髂宽指数)的重要性程度低于前者,且不同重量级别之间,各形态指标的差异性也各不相同。另外,在指标赋权基础上建立的评价体系是科学的、可行的,将为我国举重运动员科学选材提供实证意义上的参考。     

优秀男子举重运动员赛前训练的生理生化监控

目的：对国家男子举重队重点队员在2012中国举重锦标赛（奥运选拔赛）和奥运备战赛前的生理、生化指标进行监控,总结现有的赛前训练的模式,为教练员及时了解运动员的身体反应、修订训练计划和调整训练负荷、保证运动员在大赛前机能处于良好状态提供参考。方法：在国家男子举重队2012年奥运选拔赛和备战奥运的赛前期,运用生理、生化指标对国家队5个重点级别,6名运动员进行训练监控。结果：奥运选拔赛前的训练模式为赛前第2周训练强度和负荷达到最大,之后训练强度和量缓慢降低。奥运备战赛前的训练模式是大强度大负荷周与小强度小负荷周交替出现,总体呈下降趋势。选拔赛的赛前模式优于奥运备战的赛前训练模式。结论：两次赛前训练结果比较发现,锦标赛赛前训练模式优于奥运备战赛前训练;训练强度起始较大随后缓慢下降,整体训练负荷较稳定的训练可以保持运动员在赛前训练阶段的生理机能的稳定,同时提高运动员的肌肉爆发力,增强竞技状态;强度中等、训练负荷较大且整体训练量呈波动趋势的训练易于给运动员造成一定的身体不适,引起运动疲劳的积累,导致赛前竞技能力的降低。     

A notational analysis of elite tennis strategy

A notational analysis of singles events at all four Grand Slam tournaments between 1997 and 1999 was conducted to determine the influence of the sex of the player and court surface on elite tennis strategy. Rallies of 7.1 ± 2.0 s in women's singles were significantly longer than those in men's singles (5.2 ± 1.8 s P < 0.001). Rallies of 6.3 ± 1.8 s at the Australian Open, 7.7 ± 1.7 s at the French Open, 4.3 ± 1.6 s at Wimbledon and 5.8 ± 1.9 s at the US Open were recorded. Rallies were significantly longer at the French Open than at any other tournament ( P < 0.05) and significantly shorter at Wimbledon than at any other tournament ( P < 0.05). In women's singles, 52.8 ± 12.4% of points were baseline rallies, significantly more than in men's singles (28.6 ± 19% P < 0.001). The proportion of baseline rallies played at the French Open (51.9 ± 14.2% of points) was significantly greater than at the Australian Open (46.6 ± 12.5%), Wimbledon (19.7 ± 19.4%) and the US Open (35.4 ± 19.5% P < 0.05). The results show that both the sex of the player and surface of the court have a significant influence on the nature of singles tennis at Grand Slam tournaments.     

女子举重项目专项竞技实力评定的研究

采用文献资料、专家访谈、调查、测试等方法,对国家女子举重队28名运动员竞技实力进行了分析和研究,筛选出对竞技实力有显著影响的基础指标和专项指标,构建优秀女子举重运动员竞技实力评定指标体系及标准,从而为运动员竞技实力评价提供参考,对推动女子举重运动员的科学化训练提供帮助。     

山东省优秀女子举重运动员赛前竞赛动作强度训练研究

以山东省优秀女子举重运动员为调研重点,对山东女子举重运动员的赛前竞赛动作强度训练进行调研.研究表明:山东省优秀女子举重运动员大、中、小级别在赛前抓举训练强度上具有相似性,除第四周外,最高强度不低于95%,强度组数距比赛日越近,试举的强度与组教下减越明显;赛前挺举强度在95%以内;中、小级别优秀女子举重运动员耐强度优于大级别,耐强度组数也优于大级别运动员.     

女子抓举技术动作的肌电分析

运用肌电测试仪对江苏省女子举重队现役队员的抓举技术动作进行分析,选取8块在抓举过程中具有代表性的浅层骨骼肌在抓举过程做同步肌电测量。运用相关软件得出8名运动员在3个不同重量的抓举全过程中8块骨骼肌的积分肌电值,得出三角肌的积分肌电值最大,腓肠肌的积分肌电值最小。     

Three-dimensional kinematic analysis of the golf swing using instantaneous screw axis theory,Part 2: golf swing kinematic sequence

A number of recent studies have measured the extent and timing of segment rotation during the golf swing. A promising technique, instantaneous screw axis (ISA) theory, could provide a better expression of segment rotation. In Part 1 of this two-part study, the objectives are to identify the ISA of the pelvis, shoulders and left arm during the downswing, compute segment angular velocity relative to that segment’s ISA and verify that ISA theory is a valid tool to analyse segment rotation during the golf swing. Results indicate that for all subjects, at least 71% of marker velocity is a result of rotation about their respective ISA, when averaging results over the duration of the downswing, confirming that motion is primarily rotational. Furthermore, ISA position and orientation of each segment approaches, on average, the expected gross axis of rotation, confirming that motion about the ISA is representative of joint motion.     

Three-dimensional anthropometric analysis: Differences between elite Australian rowers and the general population

Abstract

The aim of this study was to quantify the anthropometric differences between elite senior Australian rowers and the Australian adult population using three-dimensional (3D) whole-body scanning. The dimensions of senior rowers competing at the 2007–2008 Australian Rowing Championships were compared with those of an age-matched sample of Australian adults. Mass, height, and sitting height were measured before the participants underwent a 3D whole-body scan, with lengths, breadths, girths, cross-sectional and surface areas, and volumes extracted from each scan. Differences in means and variability between the two groups were expressed as standardized effect sizes and ratios of coefficients of variation. Heavyweight rowers were generally much larger than the general population in absolute size, with 3D dimensions and height and mass showing the largest effects. In contrast, lightweight rowers were generally similar or smaller in absolute and proportional size. The dimensions of rowers, especially the lightweights, were also generally less variable than those of the general population. The greatest differences between elite rowers and the general population were seen in dimensions that could not be captured without 3D scanning, such as segmental volumes and cross-sectional areas.     

Start and turn performances of elite sprinters at the 2016 European Championships in swimming

The aim of this study was to examine the performance characteristics of male and female finalists in the 100-m distance at the 2016 European Championships in swimming (long-course-metre). The performances of all 64 (32-males and 32-females) were analysed (8 swimmers per event; Freestyle, Backstroke, Breaststroke and Butterfly). A set of start and turn parameters were analysed. In the start main outcome, male swimmers were faster in Butterfly (5.71 ± 0.14s) and females in Freestyle (6.68 ± 0.28s). In the turn main outcome, male and female swimmers were faster in Freestyle (males: 9.55 ± 0.13s; females: 10.78 ± 0.28s). A significant and strong stroke effect was noted in the start and turn main outcome, in both sexes. In the start plus the turn combined, males and females were faster in Freestyle (males: 15.40 ± 0.20s; females: 17.45 ± 0.54s). The start and the turn combined accounted almost one-third of the total race time in all events, and non-significant differences (p > 0.05) were noted across the four swim strokes. Once this research made evident the high relevance of start and turns, it is suggested that coaches and swimmers should dedicate an expressive portion of the training perfecting these actions.     

Skating start propulsion: three-dimensional kinematic analysis of elite male and female ice hockey players

The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete’s sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males’ maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.     

优秀射箭运动员专项技术运动学诊断指标研究

射箭运动技术诊断是该项目科学化训练的难点和要点,研究结果发现,通过超高速影像和三维红外线运动学分析的方法,以及高精度的时间、速度、位移等系列运动学指标的测量和射箭运动力学原理的综合运用,能够有效地监控射箭运动员的专项技术状态;高水平射箭运动员专项技术动作具有撒放时间短、声动反应快、箭速高、动作稳定性和一致性高的特点;另外,从功能原理与专项技术规律角度深入分析了反向动作与动作效率、动作稳定性等要素的因果关系,提出了优化撒放方式、减小反向动作幅度、增强动作控制能力是提高射箭技术水平的重要途径。     

Three-dimensional kinematic comparison of treadmill and overground running

The treadmill is an attractive device for the investigation of human locomotion, yet the extent to which lower limb kinematics differ from overground running remains a controversial topic. This study aimed to provide an extensive three-dimensional kinematic comparison of the lower extremities during overground and treadmill running. Twelve participants ran at 4.0 m/s ( ± 5%) in both treadmill and overground conditions. Angular kinematic parameters of the lower extremities during the stance phase were collected at 250 Hz using an eight-camera motion analysis system. Hip, knee, and ankle joint kinematics were quantified in the sagittal, coronal, and transverse planes, and contrasted using paired t-tests. Of the analysed parameters hip flexion at footstrike and ankle excursion to peak angle were found to be significantly reduced during treadmill running by 12° (p = 0.001) and 6.6° (p = 0.010), respectively. Treadmill running was found to be associated with significantly greater peak ankle eversion (by 6.3°, p = 0.006). It was concluded that the mechanics of treadmill running cannot be generalized to overground running.     

Discriminant analysis of anthropometric and biomotor variables among elite adolescent female athletes in four sports

The aim of this study was to identify anthropometric and biomotor variables that discriminated among groups of elite adolescent female athletes aged 14.3 ± 1.3 years (mean ± s) from four different sports (tennis, n = 15; swimming, n = 23; figure skating, n = 46; volleyball, n = 16). The anthropometric variables included body mass, height, bi-epicondylar breadth of the distal extremity of the humerus and femur, maximal girth of the calf and biceps and the sum of five adipose skinfolds. The biomotor variables were maximal aerobic power, muscular endurance and flexibility of the trunk. Discriminant analysis revealed three significant functions (P ? 0.05). The first discriminant function primarily represented differences between figure skaters and all other groups of athletes. The other two underlined anthropometric and biomotor differences between swimmers and volleyball players and between tennis players and swimmers, respectively. After validation, the analysis showed that 88% of the athletes were correctly classified in their respective sports. Our model confirms that elite adolescent female athletes show physical and biomotor differences that clearly distinguish them according to their particular sport.     

奥运冠军石智勇抓举技术运动学分析

运用三维运动学的研究方法,对参加2005年全国第十届体育运动会举重比赛的运动员石智勇的抓举技术进行运动学分析。结果表明,提铃过程中人杠重心间距控制合理,杠铃平均加速度超过2 m/s2,体现了优异的爆发力和出色的提铃技术;引膝阶段的技术与常规引膝技术已有了很大的改变,该阶段用时很短,膝关节角度也几乎没产生变化,通过对膝关节的制动充分发挥了腰背部肌肉力量,使抓举时杠铃最高加速度的值出现在引膝阶段而非发力阶段,这是最体现石智勇抓举技术特点的地方;抓举发力阶段,身体用力协调,各关节角度的把握也恰到好处;抓举下蹲支撑阶段技术动作堪称完美,人杠重心间距控制合理,杠铃回落距离仅为13.6 cm,人体重心向下的平均加速度为11.2 m/s2,两项均属于世界顶级选手的技术指标;在起立阶很好地利用了杠铃的弹性势能,与杠铃同步起立,同时人杠重心间距仅为0.002 m,确保了起立的稳定性。