排球运动员急停起跳动作中跖趾关节的生物力学分析

以20名女排队员急停起跳动作中的跖趾关节为研究对象,通过三维测力台、高速摄像机和肌电仪多机同步测试来收集运动员急停起跳中跖趾关节的运动学、动力学以及肌电数据。结果表明：1）排球运动员在急停起跳动作中,跖趾关节角度变化幅度在50°~60°之间时,运动员的起跳高度较高。建议排球运动员将急停起跳动作中的跖趾关节进行专项化训练,并采用50°~60°的跖趾关节角度变化幅度;2）排球运动员在急停起跳动作初采用足尖着地能够取得较好的起跳高度。建议排球运动员在训练及比赛中进行急停起跳动作初采用足尖着地;3）训练中,应利用跖趾关节力量训练器进行针对性训练,提高趾长伸肌、第三腓骨肌、拇长伸肌的力量值,提高跖趾关节的活化程度,进而提高运动员的起跳高度。     

Kinematic and kinetic differences in the execution of vertical jumps between people with good and poor ankle joint dorsiflexion

Abstract

The aim of the present study was to investigate the kinematic and kinetic differences in the execution of vertical jumps between individuals with good and poor ankle dorsiflexion. Fifteen physical education students were assigned to the flexible group (FG), while another 15 were assigned to the inflexible group (IFG). The two groups executed countermovement jumps (CMJ) and drop jumps from a 60 cm height (DJ60). For the CMJ, the FG jumped higher (32.0 ± 4.0 cm vs. 30.2 ± 4.9 cm, P = 0.27) and used a greater range of motion in all leg joints. The IFG jumpers raised their heels off the ground and had a greater horizontal distance between the centre of mass of the trunk and the centre of the hip joint (L_CMh 25.6 ± 3.4 cm vs. 30.9 ± 4.3 cm, P < 0.001). In the DJ60 the FG jumped higher (22.4 ± 5.9 cm vs. 19.5 ± 4.6 cm, P = 0.14) with a greater vertical shift of the body centre of mass (BCM) (S = 0.45 ± 0.11 cm vs. 0.36 ± 0.05 cm, P < 0.01) and better joint coordination. The IFG jumpers changed the position of their trunk and heels depending on the jump type. Trainers should reconsider the technical issues of vertical jumps according to the flexibility of the ankle joint.     

Kinematic repeatability of a multi-segment foot model for dance*

The purpose of this study was to determine the intra and inter-assessor repeatability of a modified Rizzoli Foot Model for analysing the foot kinematics of ballet dancers. Six university-level ballet dancers performed the movements; parallel stance, turnout plié, turnout stance, turnout rise and flex-point-flex. The three-dimensional (3D) position of individual reflective markers and marker triads was used to model the movement of the dancers’ tibia, entire foot, hindfoot, midfoot, forefoot and hallux. Intra and inter-assessor reliability demonstrated excellent (ICC ≥ 0.75) repeatability for the first metatarsophalangeal joint in the sagittal plane. Intra-assessor reliability demonstrated excellent (ICC ≥ 0.75) repeatability during flex-point-flex across all inter-segmental angles except for the tibia-hindfoot and hindfoot-midfoot frontal planes. Inter-assessor repeatability ranged from poor to excellent (0.5 > ICC ≥ 0.75) for the 3D segment rotations. The most repeatable measure was the tibia-foot dorsiflexion/plantar flexion articulation whereas the least repeatable measure was the hindfoot-midfoot adduction/abduction articulation. The variation found in the inter-assessor results is likely due to inconsistencies in marker placement. This 3D dance specific multi-segment foot model provides insight into which kinematic measures can be reliably used to ascertain in vivo technical errors and/or biomechanical abnormalities in a dancer’s foot motion.     

The position of dance in physical education

Dance has been a part of the physical education (PE) curriculum in several countries for a long time. In spite of this, studies demonstrate that the position of dance in the subject of PE is contested and that little time is devoted to dance. The overall aim of this article is to examine the position of dance as a pedagogical discourse in Swedish steering documents over time. The empirical material consists of five Swedish curricula for PE over a period of 50 years (1962–2011). Discourse analysis is used to identify organised systems of meaning, including privileged and prioritised values. Our theoretical frame of reference draws on Bernstein's concept of codes. Three different knowledge areas within dance are found in the text material: ‘dance as cultural preserver’, ‘dance as bodily exercise’ and ‘dance as expression’. Three pedagogical discourses emerge from these knowledge areas: an identity formation discourse, a public health discourse and an aesthetic discourse. The identity formation discourse in earlier curricula focuses on the perpetuation of Swedish and Nordic cultural traditions, while in later curricula, it emphasises the construction of a broader multicultural identity formation related to the understanding of different cultures. The public health discourse constitutes a prioritised understanding of dance as physical training related to a healthy lifestyle. The aesthetic discourse, which has the weakest position over time, represents the valuing of embodied experiences and feelings expressed through movements. This discourse is closely linked to the construction of gender. Over time, a new performance code came to surpass the former competence code in the steering documents. The performance code positions dance in PE as mainly a physical activity with little artistic or aesthetic value. The pedagogical discourse of dance remains within a highly disciplinary framework of social control.     

Measurement procedures affect the interpretation of metatarsophalangeal joint function during accelerated sprinting

Abstract

The metatarsophalangeal joint (MPJ) is a significant absorber of energy in sprinting. This study examined the influence of MPJ axis choice and filter cut-off frequency on kinetic variables describing MPJ function during accelerated sprinting. Eight trained sprinters performed maximal sprints along a runway. Three-dimensional high-speed (1000 Hz) kinematic and kinetic data were collected at the 20 m point. Three axis definitions for the five MPJs were compared. MPJ moments, powers and energies were calculated using different filter cut-off frequencies. The more anatomically appropriate dual axis resulted in less energy absorbed at the MPJ compared to the oblique axis which also absorbed less energy compared to the perpendicular axis. Furthermore, a low cut-off frequency (8 Hz) substantially underestimated MPJ kinematics, kinetics and the energy absorbed at the joint and lowered the estimate of energy production during push-off. It is concluded that a better understanding of MPJ function during sprinting would be obtained by using an oblique or anatomically appropriate representation of the joint together with appropriate kinematic data sampling and filtering so that high frequency movement characteristics are retained.     

Teachers as agents of change in curricular reform: the position of dance revisited

This paper reports findings from a recent large-scale survey of Physical Education (PE) teachers’ perceptions of teaching dance and compares them to results of a study completed 10 years previously [MacLean, J. (2007). A longitudinal study to ascertain the factors that impact on the confidence of undergraduate physical education student teachers to teach dance in Scottish schools. European Physical Education Review, 13(1), 99–116]. The current position of dance is examined in light of the introduction of Curriculum for Excellence (CfE) in 2010, a national initiative in Scottish schools that provides a unified flexible curricular framework for children aged 3–18. Dance remains part of the PE curriculum but also for the first time in Scotland occupies an additional position within the Expressive Arts (EA). Teachers are positioned as agents of change tasked with greater autonomy, flexibility and responsibility in curriculum design. The inclusion of dance in both PE and EA provides potential for teachers to design curricula that excludes dance from the PE curriculum or alternatively use the opportunity to increase dance provision. Currently, little is known about the impact CfE has on the provision and position of dance or the factors that impinge on teachers’ decisions regarding the inclusion of dance in the curriculum. To further such understanding, 85 secondary school PE teachers responded to a questionnaire concerning dance opportunities within the current school context. In addition, the original participants from MacLean (2007) research were re-interviewed to identify and explore the factors that enable teachers to achieve agency when teaching dance. The results indicated that collaborative planning, united goals and collective action had enabled teachers to significantly increase dance provision in schools. Teacher attention had shifted from concerns about individual capacity to a focus on the level of social, cultural and material support in providing valuable educational experiences in dance for all pupils.     

Body learning: examining the processes of skill learning in dance

This paper was stimulated by the authors' attempt to understand the process of skill learning in dance. Its stimulus was a period of fieldwork based at the Royal Ballet School in London, and subsequent discussions with the school's teachers and with academic colleagues about how it was that the young dancers developed their characteristic set of skills. The paper's focus and method is philosophical, although it draws on empirical data (albeit sparingly) where it is relevant to the discussion.

Many accounts of skill learning are premised on the presumption that learners come to know about their environment by representing it in the mind and that such representation is a result of a computational process involving information received through the senses. This is the dominant position of researchers in the field. In this paper, we discuss weaknesses in this information processing theory, and explore the elements of a more satisfactory approach. The account offered here locates dance skills within the context of development, in which skills are incorporated in learners through practice and training in dance environments. Dreyfus' theory of expertise and Bourdieu's theory of practice offer insights into the practical mastery young dancers carry in their bodies, which cannot be accurately formulated in terms of a system of representations. Dancers, from this perspective, do not passively follow instructions, but actively engage in tasks involving characteristic ways of moving that are situated in the nexus of relations between people and the distinctive contexts of dance. The paper suggests that skill learning in dance (or indeed any domain) is not a matter of processing information, but is imminent in the active, perceptual engagement of learner and context.     

调整期内大腿相对躯干转动的运动学分析

根据刚体的有限转动可分解为依一定顺序绕连体基不同基矢量的3次有限转动的原理，推导了跳雪运动员在调整期内两条大腿相对躯干的方向转换矩阵和角速度的计算公式。按照公式编制了MATLAB程序，对运动员刘树明在其调整期内大腿相对躯干的方位和角速度随时间的变化规律进行了计算，证明了公式的有效性，并且发现左、右大腿相对躯干的转动角速度在自身随体坐标系中的投影呈现强烈的“波动性”。     

Kinematic analysis of hip and knee rotation and other contributors to ballet turnout

Turnout, or external rotation (ER) of the lower extremities, is essential in ballet. The purpose of this study was to utilise physical examination and a biomechanical method for obtaining functional kinematic data using hip and knee joint centres to identify the relative turnout contributions from hip rotation, femoral anteversion, knee rotation, tibial torsion, and other sources. Ten female dancers received a lower extremity alignment assessment, including passive hip rotation, femoral anteversion, tibial torsion, weightbearing foot alignment, and Beighton hypermobility score. Next, turnout was assessed using plantar pressure plots and three-dimensional motion analysis; participants performed turnout to ballet first position on both a plantar pressure mat and friction-reducing discs. A retro-reflective functional marker motion capture system mapped the lower extremities and hip and knee joint centres. Mean total turnout was 129±15.7° via plantar pressure plots and 135±17.8° via kinematics. Bilateral hip ER during turnout was 49±10.2° (36% of total turnout). Bilateral knee ER during turnout was 41±5.9° (32% of total turnout). Hip ER contribution to total turnout measured kinematically was less than expected compared to other studies, where hip ER was determined without functional kinematic data. Knee ER contributed substantially more turnout than expected or previously reported. This analysis method allows precise assessment of turnout contributors.     

Impact of touring,performance schedule,and definitions on 1-year injury rates in a modern dance company

There is ongoing debate about how to define injury in dance: the most encompassing one or a time-loss definition. We examined the relationship between touring, performance schedule and injury definition on injury rates in a professional modern dance company over one-year. In-house healthcare management tracked 35 dancers for work-related musculoskeletal injuries (WMSI), time-loss injuries (TLinj), complaints, and exposure. The year was divided into 6 segments to allow comparison of effects of performance, rehearsal, and touring. Injuries/segment were converted into injuries/1000-h dance exposure. We conducted negative binomial regression analysis to determine differences between segments, P ≤ 0.05. Twenty WMSI, 0.44 injuries/1000-h, were sustained over one-year. WMSI were 6 times more likely to occur in Segment-6, compared with other segments (incident rate ratio = 6.055, P = 0.031). The highest rate of TLinj and traumatic injuries also occurred in Segment-6, reflecting concentrated rehearsal, New York season and performances abroad. More overuse injuries occurred in Segment-2, an international tour, attributed to raked stages. Lack of methods to quantify performance other than injury may mask effects of touring on dancer’s well-being. Tracking complaints permits understanding of stressors to specific body regions and healthcare utilisation; however, TLinj remain the most important injuries to track because they impact other dancers and organisational costs.     

古典芭蕾挥摆腿技术动作的运动学剖析

运用运动生物力学的研究方法与基本理论,对古典芭蕾舞挥鞭腿转难度动作中摆动腿的基本特点进行研究,找出该动作的内在特点与规律,建立其转体动作时摆动腿运动的相关参数指标,为今后科学训练提供相关理论依据,为诊断与分析舞蹈者的技术动作奠定必要的理论基础.     

论背越式跳高摆动腿动作的技术原理

依据背越式跳高技术的动作方法，运用运动生物力学的基本理论，从运动学和动力学的角度，对背越式跳高技术中，摆动腿在起跳阶段的3个不同时段内的技术原理进行了分析与讨论。     

Kinematic and kinetic differences between left-and right-handed professional baseball pitchers

While 10% of the general population is left-handed, 27% of professional baseball pitchers are left-handed. Biomechanical differences between left- and right-handed college pitchers have been previously reported, but these differences have yet to be examined at the professional level. Therefore, the purpose of this study was to compare pitching biomechanics between left- and right-handed professional pitchers. It was hypothesised that there would be significant kinematic and kinetic differences between these two groups. Pitching biomechanics were collected on 96 left-handed pitchers and a group of 96 right-handed pitchers matched for age, height, mass and ball velocity. Student t-tests were used to identify kinematic and kinetic differences (p < 0.05). Of the 31 variables tested, only four were found to be significantly different between the groups. Landing position of the stride foot, trunk separation at foot contact, maximum shoulder external rotation and trunk forward tilt at ball release were all significantly greater in right-handed pitchers. The magnitude of the statistical differences found were small and not consistent with differences in the two previous, smaller studies. Thus, the differences found may be of minimal practical significance and mechanics can be taught the same to all pitchers, regardless of throwing hand.     

Key motion characteristics of side-step movements in hip-hop dance and their effect on the evaluation by judges

In hip-hop dance, the elements of motion that discriminate the skill levels of dancers and that influence the evaluations by judges have not been clearly identified. This study set out to extract these motion characteristics from the side-step movements of hip-hop dancing. Eight expert and eight non-expert dancers performed side-step movements, which were recorded using a motion capture system. Nine experienced judges evaluated the dancers’ performances. Several parameters, including the range of motion (ROM) of the joint angles (neck, trunk, hip, knee, and face inclination) and phase delays between these angular motions were calculated. A quarter-cycle phase delay between the neck motion and other body parts, seen only in the expert dancers, is highlighted as an element that can distinguish dancers’ skill levels. This feature of the expert dancers resulted in a larger ROM during the face inclination than that for the non-expert dancers. In addition, the experts exhibited a bottom-to-top segmental sequence in the horizontal direction while the non-experts did not demonstrate any such sequential motion. Of these kinematic parameters, only the ROM of the face inclination was highly correlated to the judging score and is regarded as being the most appealing element of the side-step movement.     

Kinematic and kinetic variability associated with the cable put and seated rotation assessments

ABSTRACT

When new protocols are developed, there is a requirement to investigate test–retest reliability of measures for valid use and interpretation of data in research and practice. Therefore, the aim of this investigation was to determine the inter-day reliability of the cable put and seated rotation assessment protocols. On three occasions, nine resistance-trained men performed cable puts and cable rotations at different loads between 6 and 42 kg on a commercially available cable cross over machine. Load stack movement was recorded using a PT5A linear position transducer from which all kinematic and kinetic variables were calculated. Reliability was excellent for peak velocity and displacement based on intraclass correlation coefficient (ICC) and coefficient of variation (CV) across the majority of loads and movements (cable put: ICC = 0.92 to 0.99, CV = 3.1% to 8.6%; cable seated rotation: ICC = 0.76 to 0.99, CV = ?1.7% to 16.1%). However, kinetic variables demonstrated inadequate reliability across the majority of days, loads and movements (ICC = 0.70, CV >10%). It was concluded that peak velocity is a reliable kinematic measure to assess muscular capability from cable put and seated rotation protocols; however, kinetic measures are too variable to provide reliable outputs across testing occasions.     

优秀沙滩排球运动员徐林胤跳发球运动学分析

徐林胤是中国优秀男子沙滩排球运动员,曾与吴鹏根组合,获得2008年北京奥运会第九名,2010年广州亚运会冠军。对徐林胤的跳发球动作助跑起跳环节进行运动学研究,结果表明,徐林胤跳发球动作相对比较成熟,但仍存在缓冲时间过长,最大缓冲时刻膝角稍小,击球点靠后的不足,同时相关部位的肌肉力量的薄弱使得徐林胤跳发球速度受到限制。     

The three-dimensional kinetic behaviour of the pelvic rotation in maximal sprint running

The purpose of this study was to investigate the effect of lumbosacral kinetics on sprinting. Twelve male sprinters performed 50 m sprints at maximal effort. Kinematic and ground reaction force data were recorded at approximately 40 m from sprint commencement. A whole-body inverse dynamics approach was applied to calculate joint forces and torques at the hip and lumbosacral joints. The contribution of the hips and lumbosacral joint torques to pelvic rotation was subsequently calculated, with joint force powers indicating the rate of mechanical energy transfer between segments across joint centres calculated for both hip joints. The kinetic analysis indicated that the lumbosacral torsional torque contributed significantly to pelvic rotation. Additionally, the pelvic rotation exerted anterior–posterior joint forces on the hips, contributing to the large positive joint force power at the hip of the stance leg. These hip joint force powers assisted in motion recovery during sprinting. In conclusion, the lumbosacral torsional torque might contribute to the recovery motion in sprinting through application of the anterior–posterior joint forces at the hip joints via pelvic rotation.     

跖趾关节屈肌力量实验研究

采用特制的足-跖趾关节力量测试仪,对跖趾关节屈肌100%最大随意收缩力量进行了测定,并比较了16名田径运动员与16名普通大学生在该力量上的区别,为跖趾关节在下肢运动中的重要性提供依据。结果表明,跖趾关节屈肌力值约位于300~500 N之间,优势侧与非优势侧无显著性差异;该值在运动员与普通大学生之间有显著性差异,运动员是普通大学生的128%。     

中外优秀女子排球运动员跳发球空中击球动作的运动学分析

1前言20世纪90年代以后,随着新规则的实施,跳发球技术得到了飞速发展,因其冲跳距离长、击球点高、力量大、球速快、旋转强,已成为世界女排强队普遍采用的进攻性发球之一和得分主要手段。目前,中国女排在跳发球技术上,无论是在比赛中使用的人数还是使用的次数、效果方面与世界强     

2014年世界健美操锦标赛有氧舞蹈决赛前八名操化动作对比分析

运用文献资料法、录像观察法、数理统计法及对比分析法等,对2014年世界健美操锦标赛有氧舞蹈决赛前八名动作编排的技术特征进行对比分析,剖析高水平有氧舞蹈成套动作操化动作的编排特点,旨在为我国健美操有氧舞蹈项目成套动作的发展提供参考.