我国优秀女子竞走运动员身体重心运动轨迹的生物力学研究

以计算机输出的大量运动学参数与图表为依据，从运动生物力学角度分别对第8届、第9届全运会10名女子竞走运动员一个单步的身体重心运动轨迹进行定量和定性分析，并进一步分析了身体重心起伏程度与腾空时间、支撑腿踝角的关系。分析结果为，10名运动员均采用“足踵触地，踝关节背屈”滚动式的着地技术，以及后蹬腿“脚尖离地”技术，身体重心在支撑腿离地瞬时达到最大高度，在垂直支撑瞬时最低；身体重心腾空阶段的运动轨迹呈现平抛曲线而非斜上抛曲线；腾空阶段的身体重心高度差(而非身体重心总的高度差)是决定腾空时间的主要因素。     

我国优秀竞走运动员核心肌群功能性特征及其对技术的影响

目的：分析竞走运动员核心肌群的功能性特征,探讨核心肌群功能性特征对竞走技术的影响。方法：对我国6 名优秀20 km 竞走运动员主要核心肌群进行表面肌电测试和等动肌力测试。结果：（1）左右侧同名肌的MPF 和AEMG 存在显著性差异（P<0.05）。BF 和RF 协调性随运动速度的提高而下降;导致支撑腿着地时膝角减小5.5°、摆动时膝角增大15.4°。（2）核心肌群等动肌力不平衡。躯干左右侧旋转和屈伸相对峰力矩之比分别为8.7%和37%。髋膝关节屈伸肌力的总不平衡比为分别为34.3%±45.7%和18.8%±5.9%。肌力的不平衡导致支撑阶段两侧髋关节角位移差达到19.4°±9.9°,膝关为2.2°±1.6°。结论：核心肌群的上述特征将导致运动中身体稳定性的下降。建议运动员加强核心肌群的协调性与力量的平衡性训练。     

中国优秀竞走运动员技术风格及技术动作的运动学分析

采用文献资料、问卷调查、立体定点定机摄像与解析、逻辑分析和数理统计等方法,对中国优秀竞走运动员的技术风格和技术动作进行全面分析,以期为教练员、科研人员和运动员提供有益的参考。研究认为:我国优秀男子、女子竞走运动员目前的技术特点仍是在采用高步频的竞走技术风格;我国优秀男子竞走运动员均采用“足踵触地、踝关节背屈”滚动式着地技术,以及后蹬腿脚尖离地技术,符合当今世界竞走运动发展趋势。     

对我国优秀少年女子竞走运动员主要技术特征的运动学分析

采用摄像及录像解析等研究方法,对2002年"海尔斯"杯全国竞走锦标赛暨亚运会选拔赛少年女子5000米场地赛前3名运动员(年龄在17岁以下)的技术进行分析,分别拍摄每个运动员在比赛进行到1150米处、2750米处、4350米处的技术图片资料,并进行解析,以取得每个运动员一个复步的各个阶段和各个技术环节的定量数据。研究结果表明:有2名运动员的腾空时间超过了合理的腾空时限;单步身体重心垂直位移和头顶垂直位移均较大;躯干前倾后仰幅度较大;膝关节技术动作符合竞走定义的要求;运动员的足掌触地角较小。     

我国优秀女子竞走运动员竞走技术的生物力学分析

采用摄像及录像解析等研究方法 ,对我国优秀女子竞走运动员的技术进行生物力学研究与分析。研究表明 ,我国女子竞走运动员的步长、步频、着地角及支撑腿各阶段的膝角合理 ,但身体重心上下起伏偏大 (>5cm) ,并且单步腾空时间在模糊腾空时限 ,如果竞走技术不连贯、协调、轻松 ,容易造成犯规 ,需要在以后的训练中予以纠正。     

女子竞走运动员蒋秋艳竞走技术的生物力学分析

采用摄像及录像解析等研究方法,对天津师范大学优秀女子竞走运动员蒋秋艳的技术进行生物力学研究与分析。研究表明,蒋秋艳的步长、步频、足触地角度及支撑腿各阶段的膝角合理,单步腾空时间在模糊腾空时限,但身体重心上下起伏偏大(>5cm),容易造成犯规,需要在以后的训练中予以纠正。     

男子20km竞走比赛奥运冠军陈定的主要技、战术特征分析

采用影片解析法、数理统计法、专家访谈法等方法,对"全国竞走锦标赛暨奥运会达标赛"男子20 km竞走比赛冠军陈定的技术结构进行运动学分析,结合第30届奥运会的速度变化特征、各段落速度与总成绩的相互关系的研究,结果表明:我国男子20 km竞走运动员陈定的技、战术已达世界先进水平;在单步腾空时间、支撑腿膝关节角度在着地、离地瞬间,相比过去有较好的改善;身体重心垂直位移稍有加大,在竞走技术上仍然存在小步幅、快步频的特点。而运动员保持连续长时间高速度快走的竞技特征,是确保比赛获胜的关键。     

我国优秀女子20 km竞走运动员后半程竞走技术的运动学研究

运用三维运动学分析方法,对参加国际田联竞走挑战赛女子20km比赛前8名运动员后半程中一个复步进行解析。结果表明,我国运动员在后半程中,运用的是步长较短,步频较快的技术风格;腾空时间总体上处于犯规时限的下限,膝关节从着地瞬间直至垂直支撑面保持了可见的伸直状态,但在最后冲刺阶段,膝角出现了模糊伸直过程;身体重心垂直位移、头顶位置上下起伏均高于世界优秀运动员平均水平,这既与踝关节后蹬伸展离地时机偏早、用力动作不充分有关,也与着地瞬间摆动腿前摆后的前伸着地动作不够积极有关。在注意后蹬动作的同时,还应强化摆动腿积极的前摆着地动作。躯干倾角基本处于正常范围之内,但左、右腿蹬伸用力不均衡造成身体重心左、右偏差较大的情况容易导致动作外观不稳定而被判罚技术犯规。我国运动员肩髋扭转角度较小是导致步长相对较短的一个重要成因。     

山东省优秀男子竞走运动员动作技术诊断

本研究选取11名现役山东省优秀男子竞走运动员为研究对象,使用二维高速摄像,采用APAS和Dartfish动作解析软件对竞走动作进行定量分析。发现山东省多数运动员速度损失率和身体重心及头顶垂直位移波动较大,但离地踝角和踝关节角速度较为合理。少数运动员髋关节伸展不充分,导致步频过快,步幅过小。     

高红苗竞走技术诊断及分析 ANA LYSIS

以国际田联规定的竞走定义为依据, 采用高速摄影及影片解析的方法对高红苗在1994 年全国竞走锦标赛和1995 年世界杯竞走赛的竞走技术进行诊断。技术诊断结果如下: (1) 高在10km 赛程中能够保持稳定的步长, 且步长与步频合理; (2) 高的单步技术中腾空时间处于模糊腾空时限。躯干前俯角较大, 身体重心上下起伏较大, 存在被判罚腾空技术犯规的可能性; (3) 高的单步技术中前脚着时脚掌与地面的仰角合理, 支撑腿至垂直部位的膝角正确。     

Analysis of lower limb internal kinetics and electromyography in elite race walking

Abstract

The aim of this study was to analyse lower limb joint moments, powers and electromyography patterns in elite race walking. Twenty international male and female race walkers performed at their competitive pace in a laboratory setting. The collection of ground reaction forces (1000 Hz) was synchronised with two-dimensional high-speed videography (100 Hz) and electromyography of seven lower limb muscles (1000 Hz). As well as measuring key performance variables such as speed and stride length, normalised joint moments and powers were calculated. The rule in race walking which requires the knee to be extended from initial contact to midstance effectively made the knee redundant during stance with regard to energy generation. Instead, the leg functioned as a rigid lever which affected the role of the hip and ankle joints. The main contributors to energy generation were the hip extensors during late swing and early stance, and the ankle plantarflexors during late stance. The restricted functioning of the knee during stance meant that the importance of the swing leg in contributing to forward momentum was increased. The knee flexors underwent a phase of great energy absorption during the swing phase and this could increase the risk of injury to the hamstring muscles.     

Effects of volleyball match-induced fatigue on knee joint position sense

Abstract

It has been suggested that a greater number of injuries during the last third of practice sessions or matches could be related to alteration of lower limb neuromuscular control due to neuromuscular fatigue. This fatigue-related effect can be mediated by changes in joint proprioception. In athletes, the use of functional fatigue protocols could have the advantage of mimicking the demands of sporting activity, thus reflecting more specifically the changes in neuromuscular control and proprioception observed in sport settings. The purpose of the present study was to assess the effect of fatigue induced by a volleyball match on knee joint position sense in elite volleyball players. Seventeen female volleyball players aged 18.9±4.2 years from the Portuguese national team volunteered for the study. Knee joint position sense was evaluated by an open kinetic chain technique and active knee positioning, and was reported using absolute, relative, and variable angular errors. Joint position sense measures were obtained before and immediately after a simulated volleyball match of five sets. To ensure that the match was sufficiently intense to induce fatigue, the perceived exertion or exercise intensity was assessed at the end of the match using Borg’ s rating of perceived exertion (RPE) scale. All participants completed the volleyball match (90min duration), reaching or exceeding 15 on the RPE scale (15.59±0.71; range 15–17), equivalent to “hard/heavy work”. After the volleyball match, a significant increase in absolute (2.11°) and relative (1.71°) angular errors was detected. Match-induced fatigue significantly exacerbated the overestimation of the test position. Moreover, the reliability and accuracy in estimating knee angles decreased from rest to the fatigued state, as shown by the increase (264%) in variable error. Our results show that fatigue induced by a volleyball match has a marked effect on knee joint position sense in elite female volleyball players. Knee joint position sense was less accurate and less consistent after the volleyball match. Fatigue induced by a simulated competitive volleyball match resulted in proprioceptive deficits, decreasing sensorimotor system acuity in female volleyball players.     

Knee biomechanics of patients with total knee replacement during downhill walking on different slopes

Purpose:The purpose of this study was to compare knee biomechanics of the replaced limb to the non-replaced limb of total knee replacement(TKR)patients and healthy controls during walking on level ground and on decline surfaces of 5°,10°,and 15°.Methods:Twenty-five TKR patients and 10 healthy controls performed 5 walking trials on different decline slopes on a force platform and an instrumented ramp system.Two analyses of variance,2×2(limb×group)and 2×4(limb×decline slope),were used to examine selected biomechanics variables.Results:The replaced limb of TKR patients had lower peak loading-response and push-off knee extension moment than the non-replaced and the matched limb of healthy controls.No differences were found in loading-response and push-off knee internal abduction moments among replaced,non-replaced,and matched limb of healthy controls.The knee flexion range of motion,peak loading-response vertical ground reaction force,and peak knee extension moment increased across all slope comparisons between 0°and 15°in both the replaced and non-replaced limb of TKR patients.Conclusion:Downhill walking may not be appropriate to include in early stage rehabilitation exercise protocols for TKR patients.     

Support leg action can contribute to maximal instep soccer kick performance: an intervention study

This investigation assessed whether a Technique Refinement Intervention designed to produce pronounced vertical hip displacement during the kicking stride could improve maximal instep kick performance. Nine skilled players (age 23.7 ± 3.8 years, height 1.82 ± 0.06 m, body mass 78.5 ± 6.1 kg, experience 14.7 ± 3.8 years; mean ± SD) performed 10 kicking trials prior to (NORM) and following the intervention (INT). Ground reaction force (1000 Hz) and three-dimensional motion analysis (250 Hz) data were used to calculate lower limb kinetic and kinematic variables. Paired t-tests and statistical parametric mapping examined differences between the two kicking techniques across the entire kicking motion. Peak ball velocities (26.3 ± 2.1 m · s^?1 vs 25.1 ± 1.5 m · s^?1) and vertical displacements of the kicking leg hip joint centre (0.041 ± 0.012 m vs 0.028 ± 0.011 m) were significantly larger (P < 0.025) when performed following INT. Further, various significant changes in support and kicking leg dynamics contributed to a significantly faster kicking knee extension angular velocity through ball contact following INT (70–100% of total kicking motion, P < 0.003). Maximal instep kick performance was enhanced following INT, and the mechanisms presented are indicative of greater passive power flow to the kicking limb during the kicking stride.     

Knee joint coordination during single-leg landing in different directions

ABSTRACT

Knee joint coordination during jump landing in different directions is an important consideration for injury prevention. The aim of the current study was to investigate knee and hip kinematics on the non-dominant and dominant limbs during landing. A total of 19 female volleyball athletes performed single-leg jump-landing tests in four directions; forward (0°), diagonal (30° and 60°) and lateral (90°) directions. Kinematic and ground reaction force data were collected using a 10-camera Vicon system and an AMTI force plate. Knee and hip joint angles, and knee angular velocities were calculated using a lower extremity model in Visual3D. A two factor repeated measures ANOVA was performed to explore limb dominance and jump direction. Significant differences were seen between the jump directions for; angular velocity at initial contact (p < 0.001), angular velocity at peak vertical ground reaction force (p < 0.001), and knee flexion excursion (p = 0.016). Knee coordination was observed to be poorer in the early phase of velocity-angle plot during landing in lateral direction compared to forward and diagonal directions. The non-dominant limb seemed to have better coordination than the dominant limb during multi-direction jump landing. Therefore, dominant limbs appear to be at a higher injury risk than non-dominant limbs.     

我国男子竞走运动员的技术特征及生物力学分析

采用文献研究及生物力学分析等方法,对我国男子竞走运动员的技术进行分析,发现在1996年前的竞走规则和定义的影响下,我国男选手逐步形成了小步幅、快频率的技术特征。生物力学分析表明,髋的水平速度与摆动时间里高度相关,适当增加髋关节围绕身体垂直轴转动的速度,对提高步长有积极效果。控制足触地的角度和加强前摆着地技术的训练应引起重视。     

Multi-joint rate of force development testing protocol affects reliability and the smallest detectible difference

Isometric tests have been used to assess rate of force development (RFD), however variation in testing methodologies are known to affect performance outcomes. The aim of this study was to assess the RFD in the isometric squat (ISqT) using two test protocols and two testing angles. Eleven participants (age: 26.8 ± 4.5 years, strength training experience: 7.1 ± 3.03 years) completed test and retest sessions one week apart, whereby two test protocols with respect to duration and instructions were compared. Isometric peak force (ISqT^peak) and isometric explosive force (ISqT^exp) tests were assessed at two joint angles (knee flexion angle 100° and 125°). Force-time traces were sampled and subsequently analysed for RFD measures. Average and instantaneous RFD variables did not meet reliability minimum criteria in ISqT^peak at 100° or 125°. The ISqT^exp test at 100° met reliability criteria in the RFD 0–200 and 0–250ms variables. The ISqT^exp test at 125° met reliability criteria in the RFD 0–150, 0–200 and 0–250ms variables. Force-time characteristics were optimized at the higher knee joint angle. Average and instantaneous RFD measures obtained using a traditional peak force test do not meet basic reliability criteria. Researchers assessing multi-joint RFD should employ the explosive RFD test protocol as opposed to the traditional isometric peak force protocol.     

Changes in leg kinematics in response to unpredictability in lateral jump execution

Abstract

Lateral movements like cutting are essential in many team sport disciplines. The aim of the present study was to analyse adaptations in motor control in response to task unpredictability during lateral movement execution. Twelve subjects performed lateral jumps with different landing modalities (stable, sliding or counteracting) that were either known (predictable setting) or unknown (unpredictable setting) prior to movement execution. Results revealed that regardless of the landing modality, hip joint abduction was significantly greater in the unpredictable compared to predictable setting. Furthermore, during the sliding landing modality, hip flexion decreased from 211 ± 7° to 207 ± 7° and knee flexion decreased from 26 ± 4° to 24 ± 4° at the instant of ground contact in the unpredictable compared to predictable condition. During the stable landing modality, the knee joint abduction increased from ?0.3 ± 6° to ?3 ± 6° after initial ground contact in the unpredictable compared to predictable setting. The present results support our hypothesis that pre-programmed motor activity depends on the predictability of the landing modality during lateral movements. According to its adaptation in the frontal plane and in some extent in the sagittal plane, the hip joint seems to play the major role in the modulation of the pre-programmed activity for successful lateral jump execution in an unpredictable setting. However, these kinematic adaptations are concerning since these changes were associated with higher knee abduction during the stable landing modality and therefore with possible higher risk of injury.     

Comparison of 2D video and electrogoniometry measurements of knee flexion angle during a countermovement jump and landing task

Quantifying countermovement jump (CMJ) and landing knee flexion angle is important for performance and injury risk assessment. The purpose of the study was to compare electrogoniometer (El-Gon)- and video-derived CMJ and landing knee flexion angle. Twenty-two adults performed three CMJs while knee flexion angle was simultaneously assessed using an El-Gon and video. The average systematic offset (RMSE) of the El-Gon-derived knee flexion angle throughout the entire movement was 7.03°?±?2.69°. Excellent reliability was demonstrated by the El-Gon (ICCavg?=?0.92). Countermovement knee flexion angle, maximum landing knee flexion angle and flexion angle at maximum vertical ground reaction force were 12.0°, 10.9°, and 5.7° higher, respectively, when assessed using El-Gon (p?<?0.001), compared to video. Errors between instruments are likely due to El-Gon crosstalk, misalignment and/or axis determination. The El-Gon is a cost-effective and time-efficient alternative to video analysis for the assessment of knee flexion angle if the error is accounted for and the sensor is precisely attached.     

Sleep restriction impairs maximal jump performance and joint coordination in elite athletes

ABSTRACT

The study objective was to examine the effects of three days of sleep restriction on maximal jump performance and joint coordination. Eleven elite cyclists obtained a one-week baseline of habitual sleep then restricted sleep to 4 h/night (SR) for three nights assessed through self-report and actigraphy. Pre and post-intervention measures were a box drop maximal vertical jump with 3D motion capture to assess physical performance and biomechanical changes, and Psychomotor Vigilance Task (PVT) assessed changes in response time. Associations between biomechanical, physical, and cognitive performance measures were assessed. Participants restricted reported sleep from 7.4 ± 0.5 h/night at baseline to 4.0 ± 0.2 h/night and actigraphy indicated 6.7 ± 0.7 to 3.7 ± 0.2 h/night. Following SR, jump height decreased (0.44 ± 0.09 vs. 0.42 ± 0.10 m, p = 0.02, g = 0.21). Hip sagittal/knee frontal (Δ15.5°, p = 0.04, g = 0.40) and hip frontal/knee frontal (Δ11.0°, p < 0.01, g = 0.44) plane coordination variability increased after SR. Hip sagittal/knee frontal plane coordination variability after SR was associated with increasingly slower PVT response time (r = 0.63, p = 0.03). These findings suggest SR for three days decreased maximal jump performance. SR increased joint coordination variability and was associated with greater impairment in response time. SR leads to deviations from preferred movement patterns, which may have implications for decrements in athlete performance and increased injury risk.