Altered movement patterns but not muscle recruitment in moderately trained triathletes during running after cycling

Abstract

Previous studies have shown that cycling can directly influence neuromuscular control during subsequent running in some highly trained triathletes, despite these triathletes' years of practice of the cycle–run transition. The aim of this study was to determine whether cycling has the same direct influence on neuromuscular control during running in moderately trained triathletes. Fifteen moderately trained triathletes participated. Kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Muscle recruitment was different between control and transition runs in only one of 15 triathletes (<7%). Changes in joint position (mean difference of 3°) were evident in five triathletes, which persisted beyond 5 min of running in one triathlete. Our findings suggest that some moderately trained triathletes have difficulty reproducing their pre-cycling movement patterns for running initially after cycling, but cycling appears to have little influence on running muscle recruitment in moderately trained triathletes.     

Kinematic Constraints Associated With the Acquisition of Overarm Throwing Part II

The purposes of this study were to: (a) examine the differences within 11 specific kinematic variables and an outcome measure (ball velocity) associated with component developmental levels of humerus and forearm action (Roberton & Halverson, 1984), and (b) if the differences in kinematic variables were significantly associated with the differences in component levels, determine potential kinematic constraints associated with skilled throwing acquisition. Significant differences among component levels in five of six humerus kinematic variables (p < .01) and all five forearm kinematic variables (p < .01) were identified using multivariate analysis of variance. These kinematic variables represent potential control parameters and, therefore, constraints on overarm throwing acquisition.     

Kinematic Constraints Associated With the Acquisition of Overarm Throwing Part I

The purposes of this study were to: (a) examine differences within specific kinematic variables and ball velocity associated with developmental component levels of step and trunk action (Roberton & Halverson, 1984), and (b) if the differences in kinematic variables were significantly associated with the differences in component levels, determine potential kinematic constraints associated with skilled throwing acquisition. Results indicated stride length (69.3%) and time from stride foot contact to ball release (39.7%) provided substantial contributions to ball velocity (p < .001). All trunk kinematic measures increased significantly with increasing component levels (p < .001). Results suggest that trunk linear and rotational velocities, degree of trunk tilt, time from stride foot contact to ball release, and ball velocity represented potential control parameters and, therefore, constraints on overarm throwing acquisition.     

对运动影像解析中若干运动学指标算法的探讨

对运动影像拍摄与解析系统中运动学指标的可能算法进行了讨论,建议在计算（角）速度、（角）加速度等运动学指标时应当尽可能地运用中心差商的算法,在使用运动学指标时应当正确区分关节角和环节角、空间角与投影角两组概念和算法的不同,以使各种不同的解析系统计算出的运动学指标更具有可比性。     

职业运动引入体育分类体系的可行性分析

随着时代的发展，竞技运动中的商业性、市场化不断得以强化，用职业运动来代替竞技体育这一名词的时机基本成熟。体育分类体系中引入职业运动这一名词对正确认识体育的内涵，将产生较大帮助。     

Stride Adjustments during a Running Approach toward a Force Plate

Purpose

Previous research demonstrating that specific performance outcome goals can be achieved in different ways is functionally significant for springboard divers whose performance environment can vary extensively. This body of work raises questions about the traditional approach of balking (terminating the takeoff) by elite divers aiming to perform only identical, invariant movement patterns during practice.

Method

A 12-week training program (2 times per day; 6.5 hr per day) was implemented with 4 elite female springboard divers to encourage them to adapt movement patterns under variable takeoff conditions and complete intended dives, rather than balk.

Results

Intraindividual analyses revealed small increases in variability in the board-work component of each diver's pretraining and posttraining program reverse-dive takeoffs. No topological differences were observed between movement patterns of dives completed pretraining and posttraining. Differences were noted in the amount of movement variability under different training conditions (evidenced by higher normalized root mean square error indexes posttraining). An increase in the number of completed dives (from 78.91%–86.84% to 95.59%–99.29%) and a decrease in the frequency of balked takeoffs (from 13.16%–19.41% to 0.63%–4.41%) showed that the elite athletes were able to adapt their behaviors during the training program. These findings coincided with greater consistency in the divers' performance during practice as scored by qualified judges.

Conclusion

Results suggested that on completion of training, athletes were capable of successfully adapting their movement patterns under more varied takeoff conditions to achieve greater consistency and stability of performance outcomes.     

运动终板的分型及运动训练对运动终板的影响

运动终板在骨骼肌纤维上的分配是骨骼肌神经支配的表现形式,运动终板的形态结构和机能状态直接影响到肌肉的功能。它既是神经系统引起肌肉收缩的关键部位,也是肌肉疲劳的潜在衰竭点。通常,骨骼肌纤维形态改变的同时伴有运动终板形态结构的变化。因此,在运动训练条件下对运动终板的形态学研究,为加快骨骼肌纤维的收缩效率和提高运动员的成绩提供良好的理论依据。     

Physical Fitness in Children With Developmental Coordination Disorder

The protective effects of physical activity and fitness on cardiovascular health have clearly been shown among normally developed children. However, data are currently lacking pertaining to children with developmental coordination disorder (DCD). The purpose of this study was to examine differences in fitness measures, body composition, and physical activity among children with and without DCD. A cross-sectional design was implemented examining 261 children (118 girls, 143 boys) ages 4–12 years (mean age 7.8 ± 1.9 years). Children were categorized as having DCD if they scored less than or equal to the 5th percentile (n = 71) or between the 6th and the 15th percentile (n = 52) on the Movement Assessment Battery for Children (MABC; Henderson & Sugden, 1992). The typically developing children had scores between the 16th and the 50th percentile (n = 106) or above the 50th percentile (n = 32) on the MABC. The age-related body mass index was used to characterize body composition. Physical fitness was assessed with a 6-min run, 20-m sprint, jump-and-reach test, medicine ball throw, curl-ups, and sit-and-reach test. Physical activity was estimated with a questionnaire. The percentage of overweight and obese children ages 10–12 years were significantly higher in the DCD groups (severe: 50%, moderate: 23.1%) than in the typically developing groups (medium: 5.6%, high: 0%; p < .05). Significant interactions (MABC x Age Group) were found for the fitness tests (p values < .05), except flexibility; whereby specifically, compared to the children in the typically developing groups children in the DCD groups ages 4–6 years achieved significantly worse results for the 20-m sprint, and children of the DCD groups ages 10–12 years achieved significantly worse results for the 6-min run, jump-and-reach test, and medicine ball throw. The study demonstrates poorer performance in fitness tests with high demands on coordination in children with DCD compared to their typically developing peers. Furthermore, the differences in fitness increased with age between children in the DCD groups versus the typically developing groups.     

女子链球运动员米安科娃与张文秀旋转技术时空结构的运动学特征

运用文献资料、高速摄像和对比分析等方法,采用德国SIMI-moTion录像解析系统对获得第29界奥运会女子链球冠军的米安科娃和季军的张文秀的旋转阶段各时相的技术特征进行运动学解析,旨在找出张文秀与米安科娃在旋转技术上的差距,并提出有针对性的建议,为张文秀今后的训练提供理论依据,为提高我国链球运动的水平提供参考.     

基于函数型数据分析技术的运动协调量化方法应用研究

对运动协调的研究是运动控制学科的重要组成部分,其主要目的在于探索中枢神经系统等元素对机体运动控制的作用及其机制。基于运动协调的概念,矩阵分解方法被长期应用于运动协调的量化中。然而,一些量化运动协调常用的矩阵分解方法中存在的问题也日益显露。在这些矩阵分解方法中,将运动自由度表示为一个向量,作为一个具有间断特征的数据集合进行处理,是不符合实际的。这使与中枢神经运动指令有关的参数也具有间断属性,与实际由其激活的具有连续性的运动自由度状态是有矛盾的。此外,它们的量化结果与一些运动协调相关的概念不相匹配,或者是未能展现出更加丰富的运动协调相关信息。这些对量化结果的理论解释有一定程度的影响。在这此运动协调的量化问题上,函数型主成分分析技术具有特有的优势。