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1.
《Ergonomics》2012,55(1):26-45
The present study examined differences in isometric muscle capacity between older (55–65 years) and younger (18 – 25 years) individuals. A total of 24 younger and 24 older participants (gender balanced within each group) performed sustained shoulder abductions and torso extensions to exhaustion at 30%, 50% and 70% of individual maximal voluntary contraction (MVC). Along with endurance time, manifestations of localized fatigue were determined based on changes in surface electromyographic signals obtained from the shoulder (middle deltoid) and the torso (multifidus and longissimus thoracis) muscles. Strength recovery was monitored using post-fatigue MVCs over a 15-min period. Compared to the younger group, older individuals exhibited lower muscular strength, longer endurance time and slower development of local fatigue. Age effects on fatigue were typically moderated by effort level, while effects of gender appeared to be marginal. Non-linear relationships between target joint torque and endurance time were observed, with effects of age differing between shoulder abduction and torso extension. Overall, the effects of age on endurance and fatigue were more substantial and more consistent for the shoulder muscle than for the torso muscles and were likely related to differences in muscle fibre type composition. For strength recovery rates, no significant age or gender effects were found in either experiment. In summary, this study suggests that differences in isometric work capacity do exist between older and younger individuals, but that this effect is influenced by effort level and the muscle tested. 相似文献
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《Ergonomics》2012,55(2):259-265
A survey was made of the statistical techniques used in 108 papers appearing in Ergonomics between 1969 and 1971. It was found that analysis of variance techniques had been misapplied in many cases, sometimes with potentially serious consequences. The major criticisms concern the use of inappropriate error terms, the inadequate consideration of some of the assumptions involved in repeated measures and other designs, and the omission of a posteriori tests. 相似文献
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Shoulder musculoskeletal disorders (MSD) are frequently associated with the work activities that demand forceful arm exertions in pushing and pulling directions. Considering the ability of shoulder joint to exert forces in nearly any direction, our understanding of the shoulder muscles activation as affected by pushing and pulling exertions is limited. In this study the activation of seven shoulder muscles were studied for 10 male participants during pulling exertions performed in five directions (pull right, pull left, pull back, pull down and pull up) using three force levels (22.24 N, 33.36 N and 44.48 N). Exertions performed in pulling right and pulling up directions produced higher activation and received higher perceived exertion ratings than the exertions performed in the other directions. Rotator cuff and middle deltoid muscles activation were consistently higher during pulling up and pulling right exertions compared to the other muscles. A high correlation was found between the activation of rotator cuff and deltoid muscles and the perceived exertion ratings. The rotator cuff and middle deltoid muscles activation observed during the pulling up and pulling right exertions can be explained by the concavity compression mechanism which stabilizes the glenohumeral joint of shoulder.Relevance to industryThe muscle activation data expressed in terms of Maximum Voluntary Contraction (MVC) and perceived exertion ratings are widely used by the ergonomic practitioners to design and/or evaluate workplace exertions. This study provides such data for several shoulder muscles during pulling exertions performed under different conditions. 相似文献
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Purpose
To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing.Methods
Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period. Muscle activity of the medial gastrocnemius, tibialis anterior, rectus femoris and biceps femoris and venous circulation were assessed in quiet standing with the unstable shoe and barefoot.Results
In the first measurement there was an increase in medial gastrocnemius activity in all volunteers while wearing the unstable shoe. On the other hand, after wearing the unstable shoe for eight weeks these differences were not verified. Venous return increased in subjects wearing the unstable shoe before and after training.Conclusions
The unstable shoe produced changes in electromyographic characteristics which were advantageous for venous circulation even after training accommodation by the neuromuscular system. 相似文献5.
The aim of this study is to determine the effect of form factors (curvature rate, depth) of mobile devices on hand comfort when using large-screen curved mobile devices. To that end, four muscles (APB, APL, FDI, EDC) were selected and mockups for experiment were developed with four curvature rate levels (flat/100/200/300R) and five depth levels (3/5/7/9/11 mm). User experiment was conducted using three interactions (tapping, dragging, and texting) that usually take place on smartphones. EMG signal of each participant was measured. Combination of curvature and depth could maximize the physical comfort of hands and fingers through the experiment so that the interaction effect between form factors and tasks could be identified. Our results revealed that only APL and FDI had statistically significant muscle activity amounts across the curvature rates. With respect to effect of depth, all four muscles showed statistically significant difference in muscle activity. Moreover, results from the interaction effect among task levels of two tasks (target location of tapping and direction of dragging) and two form factors showed no interaction effect in either tapping or texting. The results of this study could be used to determine the optimal range for form factors of curved screen mobile devices in terms of physical comfort of the hand while using large-screen devices. 相似文献
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《Ergonomics》2012,55(12):1312-1334
Fourteen young male students (mean age 21 years, mean weight 69-4 kg, and mean height 175-4 cm) and 12 young female students (mean age 22-2 years, mean weight 60-6 kg, and mean height 169-3 cm) held 9-07 kg and 6-8 kg, respectively, at their three-quarters horizontal reach distance in upright and stooping postures for a period of 5 min. During these periods the external torque on the lumbosacral disc, intra-abdominal pressure, and electromyographic signals from erectores spinae at T12 and L3 levels, latissimus dorsi and external obliques were recorded at 1 kHz for 2-1 s every 15 s for a period of 5 min. The EMGs were processed in magnitude and time domains to determine muscle fatigue. Through the data obtained it was seen that the intra-abdominal pressure did not follow or reflect either the spinal load or the muscle activity. Based on the arguments presented, it was concluded that the intra-abdominal pressure does not appear to have a role of relieving the spine of some of its load. Instead, it is suggested that it is a dependent variable manifesting itself when mechanisms for spinal stability are evoked to overcome large voluntary and inertial loads. 相似文献
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本文以客服中心为背景,将知识库引入客服中心的建设与运营中,表达了建设客服中心知识库必要性的思想,并详细介绍了客服中心知识库的设计与实现,具有现实意义。 相似文献
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In various workplaces, gloves are commonly employed to protect the hands with the design rationale of 'the thicker the gloves, the better the protection'. Therefore, the present paper investigated the effects of glove thickness on hand performance and fatigue during two infrequent high-intensity gripping tasks, such as 5-s and sustained tasks. The hand performance was evaluated by maximum volitional contraction (MVC) and its associated time needed to reach the MVC (TMVC), and the total force generation (TFG) during the sustained task. The hand fatigue was assessed by MVC degeneration (DeltaMVC), the shift in time needed to reach the MVC (DeltaTMVC), and the maximal endurance time (MET) associated with the sustained task. Ten female subjects took part in the experiment voluntarily. The four-gloved conditions included bare hand, wearing one layer (Cotton-1), wearing two layers of cotton gloves (Cotton-2), and covering the handle with two layers of cotton glove and exerting with the bare hand (Covered-2). The results indicates that wearing gloves decreased the grip MVC, and the thicker the gloves, the less the grip MVC, but the wearing style did not change the MVC (Cotton-2 MVC was indifferent from Covered-2 MVC). As to muscular fatigue, on the other hand, wearing gloves did not affect DeltaMVC, MET, TMVC, or DeltaTMVC. Due to the greater bare-hand MVC and indifferent MET, bare-hand TFG was better than those conditions with gloves. Finally, the load specified here did not alter TMVC or DeltaTMVC, but the greater the load, the more strength degeneration (DeltaMVC) was induced. 相似文献
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本文介绍了运用Struts和Hibernate两个开源框架来设计与实现E-Learning平台,针对其中的关键技术进行分析,设计出该平台的结构、功能以及平台实现方案,并就开发过程中的几个重要问题进行了详细说明。 相似文献
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基于JSF和j2ee框架的办公自动化系统设计与实现 总被引:1,自引:0,他引:1
介绍了J2EE构架技术和办公自动化的现状,对基于JSF J2EE的办公自动化系统进行了研究,提出了基于JSF和J2EE的OA系统模型,给出了该模型的基本框架、实现方案和模型特点。在介绍了JSF技术后,以企业办公自动化系统的开发和实现为实例验证了模型的正确性和有效性。 相似文献
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针对当前网上选课系统在运行过程中不稳定等问题,本文提出了一种基于MVC模式的系统设计方案,论述了系统的功能和MVC设计模式的解决方案。将系统的业务逻辑与数据处理分离,从而使系统具有较高的运行效率、良好的可扩展性和可维护性。 相似文献
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J2EE体系的核心规范EJB对于许多中小企业的Web应用显得过于厚重,急需引入一种轻量级的Web应用框架,降低系统的实现难度和开发成本。以Spring为核心,集成Hibernate、Acegi等开源框架技术构建基于J2EE的Web应用框架,采用分层的思想,实现权限管理、信息管理等基本功能,为Web开发者提供一个轻量级的、可复用的、可扩展的框架。基于该框架实现威海市大型科学仪器共享平台的设计开发,以此说明该Web应用框架的高效性、灵活性和可复用性。 相似文献
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为探讨WebForm与MVC的共用性问题,通过对这两种技术进行详细的比较,明确了两者本质的联系与区别,指出了两者的差异性和共用性,并从技术实现的角度,分析了两者在同一应用程序中的共同应用的方法,从而肯定了两者的共用可以充分发挥ASP.NET平台的强大功能。 相似文献
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《Ergonomics》2012,55(12):2447-2454
The effect of friction and load on pinch force was studied in a simple hand transfer task using a repeated measures design and ten men. Subjects moved a container between two targets, 450?mm apart, at a slow, self-paced speed. The levels of mass in the container were set at 0·8, 2·5 and 4·2?kg (7·5, 24·5 and 41·5?N respectively). The handle materials were sandpaper and smooth aluminium. Applied pinch force was measured via a strain gauge mounted in a specially-designed handle attached to the container. Dependent variables were peak and ‘steady-state’ pinch force. The main and interaction effects of load and friction were significant. The friction effect was significant only for the highest load which, on average, elicited peak pinch forces of 16-70% of maximum voluntary force. This suggests that these men were not sensitive to friction effects at the lower loads. Results suggest that the use of tool handle friction enhancements may reduce required pinch forces for objects requiring upwards of 50% or more of maximum pinch strength 相似文献
18.
《Ergonomics》2012,55(11):1450-1461
AbstractThis study investigates foot sweat distribution with and without shoes and the relationship between foot sweat distribution and perceived wetness to enhance guidance for footwear design. Fourteen females performed low-intensity running with nude feet and low- and high-intensity running with shoes (55%VO2max and 75%VO2max, respectively) on separate occasions. Right foot sweat rates were measured at 14 regions using absorbent material applied during the last 5?min of each work intensity. Perceptual responses were recorded for the body, foot and four foot regions. Foot sweat production was 22% greater nude (p?<?.001) and with shoes did not increase with exercise intensity (p?=?.14). Highest sweat rates were observed at the medial ankle and dorsal regions; lowest sweat rates at the toes. Perceptions of wetness and foot discomfort did not correspond with regions of high sweat production or low skin temperature but rather seemed dominated by tactile interactions caused by foot movement within the shoe. Practitioner summary: This study provides a detailed view of foot sweat distribution for female runners with and without shoes, providing important guidance for sock and footwear design. Importantly, perceptions of wetness and foot discomfort did not correspond with areas of high sweat production. Instead tactile interactions between the foot, sock/shoe play an important role. Abbreviations: VO2max: maximal oxygen consumption; HR: heart rate; RH: relative humidity; GSL: gross sweat loss; Nude-I1: without socks and shoes, low intensity running; Shod-I1: with socks and shoes, low intensity running; Shod-I2: with socks and shoes, high intensity running 相似文献
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本文将J2EE组件模型、MVC设计模式和Web Services SOA技术应用于平台认证、授权、计费(AAA)系统设计中,完成AAA系统与外部信息的安全交换,且易于新应用的快速构建。目前,AAA系统已在互联星空平台中使用,具有良好的可扩展性、适用性和可靠性 相似文献