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.     

竞走项目最大速度能力和足底压力特征研究

通过二维录像解析和足底压力分布实验测试,对竞走项目运动员最大速度能力和足底压力分布特征进行相关的基础研究,以获得竞走项目运动员在特定的技术规则规定下,世界级优秀竞走运动员的极限最大速度能力、关键运动学参数和足底压力分布特征参数情况,并对这些运动学和动力学参数进行了相关分析.     

第12届全运会男、女20km竞走运动员速度特征分析

竞走速度是所有关于竞走运动技术和特征研究的首要问题,也是所有竞速项目最终要解决的问题。运用文献资料法、数理统计法、逻辑分析法对12运会男子、女子20km前8名运动员的速度特征进行分析,探求中国竞走运动员速度发展的趋势以及存在的问题,为中国竞走运动员参加2015世界田径锦标赛和2016里约奥运会提供参考。     

极点对青少年竞走技术的影响

通过极点对青少年竞走技术影响的调查分析，对竞走比赛中是否存在极点、极点反应对竞走技术有何影响等进行研究，为教练员、运动员在训练和比赛时提供参考。     

伦敦奥运会50km竞走运动员形态与竞技表现特征审视

为了研究运动员形态与竞技表现特征之间的关系,运用文献资料法、数理统计法等方法对30届奥运会50公里竞走项目运动员从身体形态特征、年龄特征、地域分布特征、速度分配特征、战术应用特征等方面进行分析,结果表明:50公里竞走项目运动员身高、体重以及克托莱指数均处于增长的趋势;30岁以上年龄运动员数量增多;世界优秀50公里运动员主要分布在欧洲,其次是亚洲与美洲,50公里前8名竞走运动员平均速度曲线呈V型,跟走和领走是50公里竞走项目主要的战术特点.建议今后对此项目运动员进行科学选材,日常训练主要进行速度强化训练.     

Inter-individual differences in stride frequencies during running obtained from wearable data

ABSTRACT

The purpose of the present study was to identify factors that underlie differences among runners in stride frequency (SF) as a function of running speed. Participants (N = 256; 85.5% males and 14.5% females; 44.1 ± 9.8 years; 181.4 ± 8.4 cm; 75.3 ± 10.6 kg; mean ± SD) shared their wearable data (?Garmin Inc). Individual datasets were filtered to obtain representative relationships between stride frequency (SF) and speed per individual, representing in total 16.128 h of data. The group relationship between SF (72.82 to 94.73 strides · min^?1) and running speed (V) (from 1.64 to 4.68 m · s^?1) was best described with SF = 75.01 + 3.006 V. A generalised linear model with random effects was used to determine variables associated with SF. Variables and their interaction with speed were entered in a stepwise forward procedure. SF was negatively associated with leg length and body mass and an interaction of speed and age indicated that older runners use higher SF at higher speed. Furthermore, run frequency and run duration were positively related to SF. No associations were found with injury incidence, athlete experience or performance. Leg length, body mass, age, run frequency and duration were associated with SFs at given speeds.

KEY POINTS

• On a group level, stride frequency can be described as a linear function of speed: SF (strides · min^?1) = 75.01+ 3.006·speed (m · s^?1) within the range of 1.64 to 4.68 m · s^?1.

• On an individual level, the SF-speed relation is best described with a second order polynomial.

• Leg length and body mass were positively related to stride frequency while age was negatively related to stride frequency.

• Run frequency and run duration were positively related to stride frequency, while running experience, performance and injury incidence were unrelated.

     

从步长、步频的角度分析我国男子百米跑成绩滞后原因

本文通过文献资料法收集国内外优秀男子百米运动员的运动技术参数,并加以统计,从影响跑速的步长、步频因素对我国男子百米跑运动员成绩滞后的因素进行分析。结果表明：我国百米运动员的步长能力不足是影响速度能力和成绩提高的主要原因,应在优化步长、步频关系的基础上,以提高步长能力为突破口,强调运动员整体训练水平的提高,从而提高最大速度能力和运动水平。     

论竞走新规则

国际田联于１９９６年初,颁布了新的竞走规则。新规则给予竞走运动一个十分明确的动作概念,其目的是将竞走动作更规范一致,使竞走定义与竞走技术相符。新的规则,赋予了竞走技术新的活力,脚尖翘起脚跟先触地、膝关节伸直的直腿着地技术动作,将成为竞走技术训练的重点。寻求既符合裁判员判罚标准、又不违反规则要求的竞走技术,将成为竞走技术训练的难点。保持合理的步频,适当增大步长,将是今后竞走技术的发展方向     

The changing shape characteristics associated with success in world-class sprinters

Abstract

The aims of this study were to identify whether relative shape and size characteristics of world-class sprinters have changed over time, and whether any anthropometric parameters characterize the most successful world-class sprinters. The results suggest that body mass index, reflecting greater muscle mass rather than greater adiposity, is an important factor associated with success in both male and female world-class sprinters over time. However, in female athletes the reciprocal ponderal index (RPI) has emerged as a more important indicator of success over several decades, with taller, more linear sprinters achieving greater success, as measured by sprint speed. In male sprinters it is only in the most recent decade that RPI has emerged as an important predictor of success. We speculate that the prominence of the RPI and an ectomophic somatotype being typical of the most successful world-class sprinters might be explained, in part, by the influence of stride length on sprint speed. In conclusion, these results suggest that coaches, selectors, and sports scientists should consider body shape when selecting potential athletes for sprint events, encouraging more linear athletes with a high RPI.     

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。     

Ground reaction forces of Olympic and World Championship race walkers

Race walking is an Olympic event where no visible loss of contact should occur and the knee must be straightened until midstance. The purpose of this study was to analyse ground reaction forces of world-class race walkers and associate them with key spatiotemporal variables. Nineteen athletes race walked along an indoor track and made contact with two force plates (1000 Hz) while being filmed using high-speed videography (100 Hz). Race walking speed was correlated with flight time (r = .46, p = .049) and flight distance (r = .69, p = .001). The knee's movement from hyperextension to flexion during late stance meant the vertical push-off force that followed midstance was smaller than the earlier loading peak (p < .001), resulting in a flattened profile. Athletes with narrower stride widths experienced reduced peak braking forces (r = .49, p = .046), peak propulsive forces (r = .54, p = .027), peak medial forces (r = .63, p = .007) and peak vertical push-off forces (r = .60, p = .011). Lower fluctuations in speed during stance were associated with higher stride frequencies (r = .69, p = .001), and highlighted the importance of avoiding too much braking in early stance. The flattened trajectory and consequential decrease in vertical propulsion might help the race walker avoid visible loss of contact (although non-visible flight times were useful in increasing stride length), while a narrow stride width was important in reducing peak forces in all three directions and could improve movement efficiency.     

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。     

Motor variability in sports: A non-linear analysis of race walking

Abstract

This aim of this study was to analyse the nature of movement variability and to assess whether entropy measures may represent a valuable synthetic index of neuromuscular organization. The regularity of kinematic/kinetic time series during race walking, the changes in the structure of intra-individual variability over the test session, and the influence of athletic skill in (inter)national rank athletes were investigated. Motion analysis techniques were used. Sample entropy (SampEn) was adopted to examine fluctuations in lower limb angles and ground reaction forces. The regularity of both original and surrogate time series was assessed and compared, by estimating SampEn, to verify the presence of non-linear features in movement variability. SampEn was statistically lower in the original data than in surrogates. In contrast, the regularity of time series did not change significantly throughout the subsequent intra-individual repetitions. Hip and ankle joint angles and vertical ground reaction force manifested increased entropy for skilled athletes. Results suggest that race walking variability was not only the product of random noise but also contained information about the inherent propriety of the neuro-musculo-skeletal system. Furthermore, they provide some indications about neuromuscular control of the lower limb joints during race walking gait, and about the differences between more and less skilled individuals.     

Step characteristic interaction and asymmetry during the approach phase in long jump

The aim of this study was to investigate the relative influence of step length (SL) and step frequency (SF) on step velocity (SV) during the approach run of high-level long jumpers and to quantify the asymmetry of these step characteristics. Spatiotemporal data of the approach run were collected during national competition from 10 long jumpers (age 26.2 ± 4.1 years, height 1.84 ± 0.06 m, mass 72.77 ± 3.23 kg, personal best performance 7.96 ± 0.30 m). Analyses were conducted for total approach, early approach and late approach. For the total approach 4/10 athletes were SF reliant and 6/10 athletes favoured neither characteristic. At the early approach, 3/10 athletes were SF reliant and 7/10 athletes favoured neither. During late approach 2/10 athletes demonstrated SL reliance, 7/10 athletes were SF reliant and 1/10 athletes favoured neither. Four athletes displayed significant asymmetry for SL and three for SF. However, no athletes demonstrated significant asymmetry for SV indicating that the asymmetrical demands of take-off do not have a marked influence on step characteristic asymmetry, probably due to the constraints of the event. Consideration should be given to the potentially conflicting demands between limbs for individual athletes.     

九运会男子百米途中跑技术分析

通过对九运会中国男子百米跑优秀运动员途中跑的技术录像解析，分析所获得的速度、角速度、步频、步长、单步各时相等运动学参数的具体指标，并与国内外优秀百米跑选手作比较，结果认为，九运会男子百米途中跑速度较以往有了明显的提高，原因主要是步长的提高，但与国外优秀选手还有差距，主要原因是步长不足；中国百米跑运动员应减少腾空时间以增大身体重心位移的支撑与腾空时间比；九运会男子百米跑运动员的摆腿及摆臂技术差异较大，且摆臂时前摆不足后摆过大，使身体产生向前的动力不足。     

关于竞走运动员“速度感”心理结构的研究

速度感是竞走运动员运动知觉和时间知觉等感知觉系统良好协调能力的一种表现。本研究设计了7项实验内容对影响速度感的多方面因素进行了单项或组合测验。结果证明,速度感是后天训练的结果。在此基础上,笔者建立了竞走运动员速度感的心理结构,并将速度感训练划分了3个主要阶段。本研究旨在为竞走运动员速度感训练提供参考依据。     

十运会男、女20 km竞走前5名运动员运动技术分析

竞走是我国田径传统的优势项目，但近年来男、女竞走运动员在国际比赛中成绩下滑。针对十运会我国男、女20km竞走前5名运动员的运动技术表现，采用新的标尺标定方法，通过二维录像平面解析研究运动员的运动技术特征。主要研究结果：竞走阶段的合理划分；步长、步频；头部速度特征；关键身体环节角度变化特征；角速度变化特征；身体垂直位移特征和运动技术视频图像信息等7个方面，并得出相应的结论。     

浅析心理训练对中长跑运动员成绩的影响

根据我国中长跑运动员目前的现状,心理因素对运动成绩的影响越来越大,赛前各种不良的心理表现,影响着他们的运动成绩。心理训练对成绩的影响越来越明显,而且心理训练也成为训练的重要组成部分之一。采用综述法和比较法对中外优秀中长跑运动员心理素质的差异来说明心理训练对运动成绩的影响,建议教练员和运动员本人在训练中有意识地培养他们对各种训练方法和训练手段的适应能力。     

Application of functional principal component analysis in race walking: An emerging methodology

This study considered the problem of identifying and evaluating the factors of individual performance during race walking. In particular, the study explored the use of functional principal component analysis (f-PCA), a multivariate data analysis, for assessing and classifying the kinematics and kinetics of the knee joint in competitive race walkers. Seven race walkers of international and national level participated to the study. An optoelectronic system and a force platform were used to capture three-dimensional kinematics and kinetics of lower limbs during the race walking cycle. Functional principal component analysis was applied bilaterally to the sagittal knee angle and net moment data, because knee joint motion is fundamental to race walking technique. Scatterplots of principal component scores provided evidence of athletes' technical differences and asymmetries even when traditional analysis (mean ± s curves) was not effective. Principal components provided indications for race walkers' classification and identified potentially important technical differences between higher and lower skilled athletes. Therefore, f-PCA might represent a future aid for the fine analysis of sports movements, if consistently applied to performance monitoring.     

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。