Effect of time on biomechanics during exercise on the functional re-adaptive exercise device

ABSTRACT

Mechanistic studies of the Functional Re-adaptive Exercise Device (FRED) have shown it automatically recruits Lumbar Multifidus (LM) and Transversus Abdominis (TrA) – two deep-spinal muscles that are atrophied and show altered motor control in low back pain (LBP). No studies have investigated the time required to familiarise to FRED exercise, which is required to inform future FRED based clinical trial protocols. This study therefore determined the effect of time, during FRED exercise, on biomechanical outcome measures, to establish the familiarisation period, and assess for loss of technique throughout a ten minute trial. A cohort comparison study of 148 participants, 70 experiencing low back pain, had lumbopelvic kinematics, exercise frequency and movement variability measured during a 10 minute trial. Magnitude-based inference was used to assess for familiarisation, using plots of variation over time with familiarised reference ranges. The no pain group took 170 seconds, and the back pain group took 150 seconds, to familiarise. A familiarisation period of at least 170 seconds (2.8 minutes) is recommended. This justifies, and provides a familiarisation time for use of the FRED as a motor control intervention.     

Seasonal variations in physical fitness among elementary school children

Abstract

There is empirical evidence that children’s physical activity is dependent on climatic conditions. In addition, a correlation between physical activity level and physical fitness has been identified. In this longitudinal study, we investigate whether seasons have an influence on physical fitness. A total of 145 German elementary school children were tested every six months over a two-year period. We used the German Motor Test 6–18 to assess physical fitness. Performance in the 6-min endurance run (P < 0.001), bidirectional jumping (P < 0.001), the standing long jump (P = 0.026), the 20 m sprint (P = 0.006) and the stand-and-reach task (P = 0.017) was significantly better in summer than in winter. There were no differences in the ability to balance backwards (P = 0.120); in the winter, the results for push-ups (P < 0.001) and sit-ups (P < 0.001) were better than those in the summer. We have shown that physical fitness is significantly influenced by the season. Consequently, when children’s fitness tests are used (e.g. as the basis for intervention programs, for classifying health-risk groups or for recognising talent), the season in which testing occurred should be reported and accounted for in future studies.     

Confirmatory Factor Analysis of the Test of Gross Motor Development-2

The purpose of this study was to examine the underlying structure of the second edition of the Test of Gross Motor Development-2 (Ulrich, 2000 Ulrich, D. A. 2000. Test of gross motor development: Examiner's manual, 2nd, Austin, TX: Pro-.  [Google Scholar]) as applied to Chinese children. The Test of Gross Motor Development-2 was administered to 626 Hong Kong Chinese children. The outlier test with standard scoring was utilized. After data screening, a total of 614 cases (N = 614) were used for further analysis. The two-factor structure of the Test of Gross Motor Development-2 was tested using confirmatory factor analysis with maximum likelihood estimation to compute parameter estimates and to select the appropriate item for each factor. The goodness-of-fit indices supported that the model was tenable (goodness-of-fit index = .95, root mean square error of approximation = .06, standardized root mean square residual = .04, comparative-fit index = .97). The findings of this study suggested that the two-factor structure proposed by Ulrich (2000 Ulrich, D. A. 2000. Test of gross motor development: Examiner's manual, 2nd, Austin, TX: Pro-.  [Google Scholar]) fit the data of Hong Kong Chinese children.     

A review of batting in men’s cricket

In this review, we critically evaluate the scientific research into the morphology and physiology of cricket batsmen. We consider all aspects of the motor control of this skill, in the context of research into dynamic interceptive actions, the biomechanics (kinematics and kinetics) of the various phases of batting strokes and injuries to batsmen. Some attention is also devoted to batting equipment and to psychological factors in batting. Because of the lack of published scientific research into women's cricket, this review focuses on the men's game and covers research on batsmen of various playing standards. For the future, we see as a high priority research into injury mechanisms, rather than simple injury statistics, and the role of cricket equipment design in injury prevention. A second priority is for multi- or inter-disciplinary research, linking the biomechanics of batting to the underlying motor control of the movements and the effect of environmental information. Biomechanical studies of the variability of the batsman's movements are needed, and these should be related to the compensatory variability proposal of ecological psychology. Clearly, there is also a need for scientific research into batting in women's cricket, which has been inadequately researched to date.     

The effect of video‐feedback on the learning of the tennis service by intermediate players

Effects of video‐feedback on improvement of the tennis service were investigated in subjects having at least 2 years of playing experience in tennis. The experiment was carried out in an indoor tennis hall under normal training conditions.

Subjects were randomly divided into three groups: a video‐feedback training (VFT) group, a traditional training (TT) group and a control group, each consisting of 22 subjects. While the subjects of the control group received no training at all, subjects in both the VFT and TT groups were trained twice weekly during 5 consecutive weeks. Each training session lasted 40 min, of which 30 min was spent on actual practice in training of the service. The remaining 10 min was spent on watching, analysing and discussing video recordings of either their own service performed during the training session (VFT group), or ground strokes and volleys of top level players (TT group). Both the VFT and TT group showed significantly greater improvements in both achievement scores and form (technique) scores than did the control group. No differences, however, could be demonstrated between the VFT and TT group, indicating that the subjects of the former group did not benefit from the video‐feedback they received.

While form scores correlated significantly (P < 0.001) with the velocity of the served ball, no such relation between form scores and spatial accuracy was apparent.     

Biomechanics feedback for rowing

Factors that affect boat speed are important determinants of rowing performance and should form the basis of feedback to rowers and their coaches. Biomechanical analysis of rowing has led to variables that are causally linked to boat speed. With modern technology, these variables can be measured and feedback can be presented instantaneously on-water, or be presented simultaneously with video after the event. This paper demonstrates the links between the criterion of success in rowing, the time for completing 2000 m and the forces acting on the boat, and describes an instrumentation system for providing feedback of these variables to rowers and coaches. These feedback techniques have been used with rowers from national to Olympic competition standard. Aspects of technique have been linked to the determinants of boat speed and several examples are presented here. The motor learning literature supports the effectiveness of kinetic information feedback for the improvement of motor skill and provides a relevant conceptual framework for the improvement of rowing performance. However, although rowers and their coaches value this feedback, further research must be undertaken to establish a sound basis for comparing the effectiveness of such feedback compared with traditional styles, such as verbal feedback of performance.     

Modelling coaching practice: the role of instruction and demonstration

In this paper, we review the empirical literature pertaining to the effectiveness of instructions and movement demonstrations. Initially, we examine existing theories and approaches that try to explain the process of skill acquisition so as to determine implications of these theories for instructional provision. This is followed by an evaluation of studies in the motor learning literature in which pre-practice information has been manipulated. Explicit learning strategies are contrasted to implicit and discovery learning methods, and current explanations for instructional effects are discussed in terms of such mechanisms as effects-related attentional focus and movement variability. In the final sections, we review data from our own laboratory where pre-practice information has been manipulated during the learning of a novel bimanual coordination task. From these studies, proposals are made to try and explain how pre-practice information works to effect the process of skill acquisition, including the selection and execution of a response and the processing of associated feedback. An important role is given to the existing skills of the learner in understanding the instructions and performing the desired movement. Finally, we suggest some practical implications of this empirical evidence for the teaching of motor skills.     

双馈电机双三电平调速系统的研究

本文在简化三电平空间矢量脉宽调制算法的基础上,以双馈电机为控制对象,重点研究了其在定子磁链定向下的控制技术;主电路采用双三电平背靠背拓扑结构,分别论述了其中前端整流器与末端逆变器的控制方法,并通过仿真进行了验证;搭建了一套实验平台,给出了器件选型方法,同时对系统软、硬件结构进行了详细描述,最后通过实验证明了文中所提控制策略与软、硬件的设计都是正确、有效的。     

从运动技能学习的“高原现象”看我国地市级体校训练管理的弊端

多数地市级体校把向上级体校或专业运动队输送运动员,在各级竞技比赛中夺取奖牌的数量作为教练员的责任目标,并把完成目标的结果与教练员的福利、待遇挂钩。而这个年龄段的青少年运动员,在校期间大多处于运动技能学习中的“高原现象”期,运动技能提高缓慢,甚至停滞、下降。教练员为了完成其责任目标,往往采取“揠苗助长”式的训练方法,进行大运动量、高强度超负荷的训练,或使用不合理的营养补剂,违犯了运动训练的科学规律,影响了青少年运动员的身心健康;也使不少未突破“高原现象”期而具有良好运动潜力的青少年运动员被淘汰,造成人、财、物的浪费。最后提出了改变这一局面的建议     

直流电机的基本工作原理与结构教学方法探讨

围绕直流电机的基本工作原理与结构这节课的重点和难点,结合教学实践,从导语设计、激疑教学、多媒体教学、教材内容处理等4个方面对其教学方法进行了讨论,以期对教学同行提供借鉴.