The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking     

Taeyou Jung  Yumi Kim  Hyosok Lim  Konstantinos Vrongistinos 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(3):297-307

The purpose of this study was to investigate kinematic and spatiotemporal variables of aquatic treadmill walking at three different water depths. A total of 15 healthy individuals completed three two-minute walking trials at three different water depths. The aquatic treadmill walking was conducted at waist-depth, chest-depth and neck-depth, while a customised 3-D underwater motion analysis system captured their walking. Each participant’s self-selected walking speed at the waist level was used as a reference speed, which was applied to the remaining two test conditions. A repeated measures ANOVA showed statistically significant differences among the three walking conditions in stride length, cadence, peak hip extension, hip range of motion (ROM), peak ankle plantar flexion and ankle ROM (All p values < 0.05). The participants walked with increased stride length and decreased cadence during neck level as compared to waist and chest level. They also showed increased ankle ROM and decreased hip ROM as the water depth rose from waist and chest to the neck level. However, our study found no significant difference between waist and chest level water in all variables. Hydrodynamics, such as buoyancy and drag force, in response to changes in water depths, can affect gait patterns during aquatic treadmill walking.  相似文献   

Examining the influence of grip type on wrist and club head kinematics during the golf swing: Benefits of a local co-ordinate system     

Howie J. Carson  Jim Richards  Bruno Mazuquin 《European Journal of Sport Science》2019,19(3):327-335

Wrist movements have been identified as an important factor in producing a successful golf swing, with their complex motion influencing both club head velocity and orientation. However, a detailed analysis of wrist angles is lacking in the literature. The purpose of this study was to determine kinematics across wrists and club head characteristics during the golf swing under weak, neutral and strong grip conditions. Twelve professional male golfers executed 24 shots using a driver under three grip conditions. A six degrees of freedom analysis of the hand with respect to the distal forearm was performed using a 10-camera three-dimensional motion capture system. Differences in joint angles were explored using repeated measures ANOVAs at key swing events (onset, top of backswing and impact), in addition club head velocity and clubface angle at impact were also explored. Main findings revealed significant differences in flexion/extension and internal/external rotation for both wrists at all swing events, whereas fewer significant interactions were found in ulnar/radial deviation across grips for both wrists at all events. Clubface angle only differed significantly between the weak and the strong and neural grips, presenting a more ‘open’ clubface to the intended hitting direction. This study is the first to explore tri-planar wrist movement and the effect of different grips, such analysis has implications for coaching knowledge and practice and should inform future research into different aspects of skill, technique analysis and may inform injury mechanisms/prevention.  相似文献   

Between-limb differences in running technique induces asymmetric negative joint work during running     

Satoru Hashizume  Hiroaki Hobara  Yoshiyuki Kobayashi 《European Journal of Sport Science》2019,19(6):757-764

Negative work, which is mainly generated by eccentric muscle contraction, has an important influence on the associated muscle damage. Generally, mechanical parameters are determined for one side of a lower extremity on the assumption of negligible between-limb differences. However, between-limb differences in the negative work of lower extremity joints during running remain unclear. This study examines between-limb differences in negative work and associated mechanical parameters during the contact phase of running. Twenty-five young adult males voluntarily participated in this study. Each participant was asked to run on a straight runway at a speed of 3.0?m?s^?1. Negative work, amplitude, duration of negative power, moment, and angular velocity were computed for both sides of the lower extremities. Significant differences were found in negative work between limbs for the hip (18.9?±?11.7%), knee (13.6?±?10.4%), and ankle (11.8?±?8.5%) joints. For the hip joint, asymmetric negative work was attributable to the between-limb difference in the amplitude of negative power owing to a corresponding difference in the moment. The between-limb differences concerning the duration and amplitude of negative power could explain the asymmetric negative work in the knee joint. The asymmetric negative work of the ankle joint was attributable to the between-limb difference in the amplitude and duration of the negative power and the moment. These results indicate that asymmetric negative work was generated in each lower extremity joint; however, the major mechanical parameters corresponding to the negative work are not the same across the joints.  相似文献   

Contextual factors on physical demands in professional women’s soccer: Female Athletes in Motion study     

Jason D. Vescovi  Olesya Falenchuk 《European Journal of Sport Science》2019,19(2):141-146

The aim of this study was to examine the impact of contextual factors on relative locomotor and metabolic power distances during professional female soccer matches. Twenty-eight players (forwards, n?=?4; midfielders, n?=?12; defenders, n?=?12) that competed in a 90-min home and away match (regular season only). The generalised estimating equations (GEE) was used to evaluate relative locomotor and metabolic power distances for three contextual factors: location (home vs. away), type of turf (natural vs. artificial), and match outcome (win, loss and draw). No differences were observed for home vs. away matches. Moderate-intensity running (20.0?±?1.0?m?min^?1 and 16.4?±?0.9?m?min^?1), high-intensity running (8.6?±?0.4?m?min^?1 and 7.3?±?0.4?m?min^?1) and high-metabolic power (16.3?±?0.5?m?min^?1 and 14.4?±?0.5?m?min^?1) distances were elevated on artificial turf compared to natural grass, respectively. Relative sprint distance was greater during losses compared with draws (4.3?±?0.4?m?min^?1 and 3.4?±?0.3?m?min^?1). Overall physical demands of professional women’s soccer were not impacted by match location. However, the elevation of moderate and high-intensity demands while playing on artificial turf may have implications on match preparations as well as recovery strategies.  相似文献   

Comfort assessment of running footwear: Does assessment type affect inter-session reliability?     

Julia Lindorfer  Josef Kröll  Hermann Schwameder 《European Journal of Sport Science》2019,19(2):177-185

Assessing comfort of running footwear reliably is challenging. The purpose of this study was to compare the intra-rater reliability between different assessment types, to calculate intra-individual reliability scores and to evaluate the effect of rater selection based on individual reliability scores on group level reliability. Three assessment types: ranking, Visual Analogue Scale (VAS), and Likert Scale (LS) were provided twice in six separate sessions among 30 participants, who assessed comfort of five shoes after treadmill running. Spearman's rho provided an evaluation of inter-session relative reliability and typical error as a measure of absolute reliability for each assessment type. Ranking (r?=?0.70, 95% confidence interval [CI] 0.61–0.78) yielded the highest relative reliability for overall comfort, followed by VAS (r?=?0.67, 95% CI 0.56–0.75) and LS (r?=?0.63, 95% CI 0.52–0.72), with large-scale overlaps of CIs between assessment types. The same order of assessment types was found for the percentage of reliable raters (r?≥?0.7) with 60% in ranking scale, 47% in VAS and 37% in LS. Forming subgroups corresponding to the intra-individual reliability substantially increased group level reliabilities. Based on measures of relative reliability, an extreme reduction in resolution as provided by the ranking from pairwise comparisons seems to be a valuable tool in footwear comfort assessments if assessment time is of minor importance. No preference can be provided for the two investigated rating scales. Besides the assessment type, a selection of the best raters in additional reliability checks seems to be a prerequisite for further comfort-related studies.  相似文献   

对韩国文献太极拳理论研究的计量学分析*     

焦〓春  李爱增 《广州体育学院学报》2019,(1):60-64

太极拳是我国首批非物质文化遗产,作为中国传统民族特色的文化形态,近年来也越来越受到世界各国人民的喜爱,在世界范围内影响广泛、传播迅速。通过对韩国学术界的太极拳文献进行计量学统计分析,着重分析了文献的发表时间、作者、发行单位、研究主题和研究方法,旨在研究太极拳在韩国的发展史和传播过程,从社会学、文化学、体育学、传播学等角度,探索太极拳在异国推广和传播的规律及有效的推广方法,以期太极拳在世界大舞台上发扬光大,将太极拳的正能量传播到世界的各个角落。  相似文献   

体育明星电视广告代言研究          下载免费PDF全文

孙文树 《河北体育学院学报》2019,33(1):28-33

以中央五频道2013—2015年间播放的电视广告为样本,采用内容分析法对体育明星的电视广告代言情况进行分析。结果显示：①体育明星进行电视广告代言的比例非常高,占27.66%;而在电视商业广告中,这一数字达到了36.05%,说明体育明星在电视广告中的流行程度非常高。②电视广告中体育明星的代言内容十分广泛,以汽车、公益、体育用品、酒类、赛事、媒体、企业形象、饮品等八类为主,并且体育相关产品的51.0%、非体育相关产品的25.7%都是由体育明星来代言的。③体育明星代言电视广告的数量与奥运会密切相关,企业选择体育明星作为代言人受体育明星的流行程度、匹配性、领域地位等因素的影响。④未来体育明星电视广告一定程度上会受移动广告的冲击,但是体育娱乐化也进一步拓宽了体育明星代言电视广告之路。  相似文献   

三种国产兰属植物核型研究及其系统分类学意义     

雷文瑾  谢强  韦仕堂  卢柳燕  张海峰 《河池学院学报》2007,27(5):65-68

分析3种国产兰属植物,即春兰、春剑、惠兰的核型,并结合已有的形态学及核型资料对其分类及核型进化进行了初步的讨论,结果表明这3种兰属植物的染色体数目比较保守,变异不大,并且核型也具有较高的对称性。3种兰属植物的染色体核型差异与形态差异具明显的对应相关关系,说明兰属植物的形态变化更多的与遗传因素有关。  相似文献   

基于情境感知的电商平台推荐系统框架研究     

程秀峰  张孜铭 《情报理论与实践》2021,44(2):168-177

[目的/意义]随着互联网行业的蓬勃发展,电商平台的用户与商品数量均呈现井喷增长。这一趋势在促进互联网经济发展的同时也为用户带来了"信息过载"的问题。电商平台如何从用户的历史行为日志中获取信息,并根据用户当前情境推荐商品,不仅是重要的理论与技术课题,同时也蕴藏着巨大的商业价值。[方法/过程]文章结合情境感知技术,提出了一种五层推荐系统框架,自底向上分为:感知层、过滤层、排序层、规则层和应用层。同时,利用淘宝APP的购物数据进行了模拟推荐实验,比较了各层次不同设计方式的推荐效果。[结果/结论]研究发现,融入了情境感知技术的推荐系统框架可以显著提高推荐的精确率,但是会削弱召回率。基于此,为电商平台提出了部分建议。  相似文献   

双边市场、多边市场与经济高质量发展——分工网络的超边际一般均衡分析     

郑小碧  季垚 《研究与发展管理》2022,34(2):27-40

随着传统经济时代向数字经济时代的变迁,市场组织模式不断从单边市场向双边市场和多边市场转型升级。本文将市场组织模式的转型视为分工网络的演进过程,运用超边际分析和数字模拟方法揭示单边市场向双边及多边市场转变的内在机制及条件,并阐释这一结构变化对经济高质量发展的影响效应。研究发现,当综合学习成本较低时,市场交易效率的充分改进将驱动单边市场、双边市场和多边市场顺次成为均衡模式;当综合学习成本和市场交易效率都较高时,单边市场将被逼迫向双边市场和多边市场转型;当综合学习成本很高时,无论市场交易效率多高,多边市场都是唯一的均衡模式;单边市场向双边和多边市场模式的转型伴随着产业资本化程度的上升,这有利于数字经济发展初期单边市场向双边市场的转型,但却不利于中后期多边市场的形成与发展,资本过度无序扩张不利于数字市场的可持续发展;标准化程度越高的产品越会选择双边市场交易模式,而标准化程度越低的复杂产品则更倾向于选择多边市场交易模式;市场组织模式变迁通过提升劳动生产率、优化劳动力资源配置、促进市场有效供给增长、激发经济发展活力和提升人均真实收入等促进经济的高质量发展。  相似文献