Changes in ankle joint stiffness due to stretching: The role of tendon elongation of the gastrocnemius muscle

Abstract

The purpose of this study was to investigate changes in ankle joint stiffness and the associated changes in the gastrocnemius muscle and tendon due to static stretching. Seven healthy male participants lay supine with the hip and knee joints fully extended. The right ankle joint was rotated into dorsiflexion from a 30° plantar flexed position and the torque measured by a dynamometer. The ankle joint was maintained in a dorsiflexed position for 20 min (static stretching of the calf muscles). We performed surface electromyography of the medial and lateral gastrocnemii, the soleus, and the tibialis anterior of the right leg to confirm no muscle activity throughout static stretching and the passive test (passive dorsiflexion). During static stretching, the ankle joint angle and elongation of the gastrocnemius were recorded by goniometry and ultrasonography, respectively. Tendon elongation of the gastrocnemius was calculated based on the changes in the ankle joint angle and muscle elongation. In addition, the relationships between passive torques and ankle joint angles, and elongation of muscle and tendon, were examined before and after static stretching. The ankle dorsiflexion angle and tendon elongation increased significantly by 10 min after the onset of static stretching, while there was no further increase in muscle length. In addition, ankle dorsiflexion angle and tendon elongation at an identical passive torque (30 N · m) increased significantly (from 24±7° to 33±5° and from 17±2 mm to 22±1 mm, respectively) after static stretching. However, muscle elongation was unchanged. In conclusion, the current results suggest that an increase in the ankle joint dorsiflexion angle due to static stretching is attributable to a change in tendon not muscle stiffness.     

Lower extremity joint loads in habitual rearfoot and mid/forefoot strike runners with normal and shortened stride lengths

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2–14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: ?9.9 ± 0.9, hFF-FFS: ?9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one’s SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads.     

A constrained linear quadratic optimization algorithm toward jerk-decoupling cartridge design

Linear direct feed drives are widely used in machine tools, but an abrupt counter force from the secondary part will induce the jerk to the metro frame contacted with the linear motor and cause the vibration of auxiliary devices on it. The jerk-decoupling cartridge (JDC) provides a buffer to reduce such an impact. Design target for such a system includes both the tracking error and the jerk induced to the metro frame. To achieve both targets systematically, this work presents an integrated approach to efficiently determine parameters in the JDC and the position controller of the feed drive. The problem is firstly formulated as a nonlinear constrained optimization problem, which is then converted to a series of projection gradient optimization problems and step searching problems, which are either convex or linear. Thus, fast convergence of parameters are achieved within first several iterations. Through a series of simulation, the effectiveness of proposed methodology is verified.     

Co-analysis of work in the triadic supervision of preservice teachers based on neo-Vygotskian activity theory: Case study from a French university institute of teacher training

The goal of this study was to evaluate the effects of the joint training activities of a cooperating teacher and a university supervisor during an advisory visit on (a) the professional development of a preservice teacher's activity and (b) the reorganization of mentoring activity following this visit. The results are considered from a theoretical perspective based on cultural-historical psychology (Leontiev, A. (1984). Activity, consciousness, personality. Moscow: Progress Editions.; Vygotsky, L. S. (1978). Interaction between learning and development. In: M. Cole, V. John-Steiner, S. Scribner & E. Souberman (Eds.), Mind in society (pp. 79–91). Cambridge: Harvard University Press.; Vygotsky, L. S. (1997). Thought and language. Paris: La Dispute.; Vygotsky, L. S. (2003). Consciousness, the unconscious, emotions. Paris: La Dispute.) and the clinical study of activity (Clot, Y. (2003). Vygotsky, consciousness as liaison. In: Vygotsky, consciousness, the unconscious, emotions. Paris: La Dispute, pp. 7–59.; Clot, Y. (2004). Work between functioning and development. Bulletin de Psychologie, 57(1), 5–12.; Clot, Y. (2008). Work and the power to act. Paris: PUF.; Clot, Y., & Faïta, D. (2000). Types and styles in work analysis. Concepts and methods. Travailler, 6, 7–43.). The discussion focuses on the conditions that led to the greater effectiveness of the advisory visit, which is an integral part of teacher training programs that alternate classroom work with co-analysis of the work. Proposals are also made for new directions in training supervisors and cooperating teachers with a view to building a training team.     

联合图书馆高质量的管理模式探索

针对由多个图书馆建立的联合图书馆在管理方面的复杂特点,分析了联合图书馆的建立目的、组成形式和实践应用过程的种种问题。从图书馆的组织结构、运行机制、管理方式等方面进行深入研究,寻找合适联合图书馆管理策略,提出了面向联合图书馆的高质量管理模式,并通过建立监督反馈机制,在运行过程中对联合图书馆的管理制度和措施不断进行完善。     

Skills versus pedagogy? Doctoral research training in the UK Arts and Humanities

The traditional ‘lone scholar’ view of an Arts and Humanities doctoral student sits uneasily with the skills-based discourse underpinning policies aimed at enhancing researcher development and employability. This paper reports on a case study of a research training programme for doctoral students in the Arts and Humanities at a UK university. It calls for the embedding of the generic skills agenda within a more clearly articulated pedagogic discourse and formulates four pedagogic principles for research training programme design. Additionally, the paper problematises the research trainer role and highlights the importance of paying attention to the students' own learning agendas and the learning value they are prepared to derive from training.     

The determinants and impact of private tutoring classes in Vietnam

Private tutoring is a widespread phenomenon in many developing countries, including Vietnam. Using the Vietnam Living Standards Surveys 1997–1998 and 1992–1993 for analysis, this paper finds evidence that private tutoring in Vietnam is a necessity in the household budget for both primary students and lower secondary students, and the trend to attend private tutoring is stronger at higher education levels. There is no evidence of gender discrimination in expenditure on private tutoring. Ethnic minority students spend less on private tutoring at the primary level but not at the lower secondary level, as do students living in rural areas. However, spending on private tutoring would fall significantly if the qualifications of primary school teachers are increased. Private tutoring is found to have significant impact on a student's academic performance, but the influence is larger for lower secondary students. This paper contributes to the available estimation techniques by extending the simultaneous Tobit model of Amemiya [(1974). Multivariate regression and simultaneous equation models when the dependent variables are truncated normal. Econometrica, 42(6), 999–1012] to a joint Tobit-ordered probit econometric model to address the possible endogeneity of household spending on private tutoring.     

抗日战争时期湖北中等学校的内迁和湖北联中的成立

抗日战争时期,湖北省政府为了抢救战区学校,保存湖北教育的基础,将湖北战区各类公私立中等学校合并,组建“湖北联中”,统一迁往鄂西,鄂北后方各县。这是抗战时期湖北中等教育的一次重大战略转移和战略调整,也是湖北近代教育发展史上的一次重大转折。本考察了这次内迁的历史背景和具体经过。分析了其历史成效和不足之处。     

校企联合复合型双语人才培养模式探究

随着外向型经济贸易的发展,大中型企业对外进行经济合作和文化交流也愈加频繁,外语在经济发展中发挥着越来越重要的桥梁作用。培养大批既懂专业又懂外语的高素质复合型双语人才,是目前职业技术教育培养目标的新要求。校企联合复合型双语人才培养模式无疑是实现双语人才培养目标的重要途径。     

C++Builder调用Matlab工具箱技术及其应用

本文利用Matlab神经网络工具箱建立教学质量评价的BP网络模型,结合Borland C Builder自身具有的丰富可视化组件和数据库管理功能,通过ActiveX和BDE技术进行混合编程,来做出科学化的评价结果。