Maximal oxygen uptake during cycling is reduced in moving environments; consequences for motion-induced fatigue

In previous studies on physical fatigue during simulated ship movements, the apparent exhaustion of subjects after experimentation suggested that the traditional index of physical workload, oxygen consumption expressed as the percentage of peak oxygen consumption ([Vdot]O_2-peak) measured in a separate graded exercise test (GXT), underestimates workload in a moving environment. In these studies, the GXT was carried out in a stationary environment, as is standard practice. To explain the underestimation, it was hypothesized that [Vdot]O_2-peak might have been less if the GXT had been carried out in the moving environment. This paper reports on three experimental tests of this hypothesis, performed with a ship motion simulator and aboard a ship at sea. In all three experiments, [Vdot]O_2-peak was indeed significantly reduced when the GXT was carried out in the moving environment. Theoretical reasons for this phenomenon are discussed and investigated, but a clear explanation is still lacking.     

Postural and trunk muscle response to sudden release during stoop lifting tasks before and after fatigue of the trunk erector muscles

The effect of fatigue on the muscular and postural response to sudden release of different stoop lifting loads was studied. Ten male volunteers performed a series of stoop lifting trials before and after fatigue of the erector spinae. Trials were performed using loads of 20, 40, 60, and 80N, and sudden release of load was triggered randomly on one of the repetitions using an electromagnetic release. The onset of release was registered by an accelerometer, centre of pressure (COP) motion was recorded via a forceplate, and EMG activities of the latissimus dorsi (LD), erector spinae (ES), rectus abdominus (RA), external oblique (EO) and internal oblique (IO) muscles were recorded. A slightly reduced lifting speed was seen after fatigue, particularly at the higher loads, but this had little effect on the perturbing force at release, which was dominated by the release load. A significant effect of fatigue was seen on the antero-posterior COP motion, with the postural disturbance being decreased after fatigue. Fatigue resulted in a significant increase in ES (p = 0.029) and LD (p = 0.015) relaxation times and, while the response patterns (relaxation, contraction or no response) of the anterior trunk muscles (RA, EO, IO) were not always consistent, the proportion of response by relaxation was greater after fatigue. This resulted in a lower incidence but longer duration of co-contraction of the ES-RA, ES-EO and ES-EO muscle groups following fatigue, such that the mean co-contraction duration of these groups showed no significant differences before and after fatigue. The response to sudden release is a balance between maintaining postural stability and at the same time preventing the trunk musculature from overloading the spine and risking tissue injury. While fatigue of the trunk extensors does not appear to increase either the risk of fall or stumble or the incidence of co-contraction following sudden release of stoop lifting tasks, the duration of co-contraction appears to increase following fatigue. Further study is required to quantify the loading on the spine during sudden release of different lifting tasks before and after more realistic fatigue conditions.     

Changes in stature following plyometric drop-jump and pendulum exercises

The aim of this study was to compare the changes in stature following the performance of plyometric exercises using drop-jumps and a pendulum swing. Eight male participants aged 21.7 ± 1.8 years with experience of plyometric training gave their informed consent to act as participants. Participants undertook two exercise regimens and a 15-min standing test in a random order. The exercises entailed the performance of 50 drop-jumps from a height of 0.28 m or 50 pendulum rebounds. Participants were instructed to perform maximal jumps or rebounds using a ‘bounce’ style. Measurements of stature were performed after a 20-min period of standing (pre-exercise), 2-min after exercise (post-exercise) and after a 20-min standing recovery (recovery). Back pain and muscle soreness were assessed using an analogue-visual scale, at each of the above times and also 24 and 36 h after the test. Peak torque during isokinetic knee extension at 1.04 rads^?1 was measured immediately before and after the exercise bouts, to assess the degree of muscular fatigue. Ground/wall reaction force data were recorded using a Kistler force platform mounted in the floor for drop-jumps and vertically on the rebound wall for pendulum exercises. Drop-jumps resulted in the greatest (p<0.05) change in stature (-2.71±0.8 mm), compared to pendulum exercises (-1.77±0.7 mm) and standing (-0.39±0.2 mm). Both exercise regimens resulted in a significant (p<0.01) decrease in stature when compared to the standing condition. Dropjumps resulted in significantly greater peak impact forces (p<0.05) than pendulum exercises (drop-jumps = 3.2±0.5 × body weight, pendulum = 2.6±0.5×body weight). The two exercise conditions both invoked a small degree of muscle soreness but there were no significant differences between conditions. Both exercise regimens resulted in a non-significant decrease in peak torque indicating a similar degree of muscular fatigue. Based on the lower shrinkage resulted and lower peak forces, it can be concluded that pendulum exercises pose a lower injury potential to the lower back than drop-jumps performed from a height of 28 cm.     

Changes in Subsidiary Reaction Time and Heart-Rate During Car Driving,Passenger Travel and Stationary Conditions*

Distinction can be drawn between three types of letter sorting machines and these types can also be used to classify other kinds of machine and task. In one type (‘paced ’) the speed of operation is set by the machine : in another (‘ unpaced’) the speed is determined by the operator's own actions, and in a third (‘ lagged ’) the speed is determined by the operator, but a minimum time (a ‘ time lag ’) has to elapse between one operation and the next. The performance of 7 operators on a lagged letter sorting machine was observed over a period of 9 months. Records were taken of mean sorting rate, and of the distribution of sorting times. Practice effects are shown to have been continuing at the end of this period, and it is argued that the distribution of sorting times has been affected by the machine' lag.

By assuming a distribution that would be expected if there were no lag, tables are presented which estimate what the sorting rate would be (a) if there were no log at all, (b) for different values of lag and (c) for different values of paced rate.     

Changes in oculomotor functions before and after loading of a 3-D visually-guided task by using a head-mounted display

Changes in visual and oculomotor functions were tested in eight young volunteer subjects after performing a 3-D visually-guided task for 25min. The visual stimuli were given by using a head-mounted display. No significant change was detected in the AC/A ratio and the stereo-acuity. Changes were found in refraction and ocular convergence. Slight but significant hyperopic changes were detected in refraction after the task. The mean amplitude of convergence eye movement elicited by test Stimuli after the task was significantly changed in the pooled data. They were significantly reduced when the subjects were tested by the disparity step of 0.7°, but significantly increased when tested by the step of 6°. The mean amplitudes were not significantly changed after the task when the subjects were tested by the intermediate disparity steps of 1.5 and 3°. In data obtained for each subject, the amplitude of ocular convergence evoked by test stimuli after the task was reduced significantly in most subjects. In the majority of subjects, however, the results were not consistently significant when they were tested by step stimuli with different disparities. In only a few subjects, the changes were consistently significant except when the largest disparity was tested. On the other hand, the mean peak velocities of ocular convergence after the task were not significantly changed in the pooled data. In individual subjects, the changes of velocities of ocular convergence evoked by test stimuli after the task were more variable: they increased in some subjects but decreased in other subjects. Consequently, in only one subject, both amplitudes and peak velocities of ocular convergence tested by the-disparity steps of 0.7, 1.5 and 3° were consistently reduced after the task. The changes in refraction or ocular convergence found in this study were relatively small, and were not in the pathological range. The significance of these data are discussed. The results of the present study provide the basis for the more detailed analyses of the human factor in the head-mounted display.     

A study on the capacity of a ventilation cooling vest with pressurized air in hot and humid environments

Hot and humid working environments exist in civil engineering, exploration, shipping, and so on. Especially in mines and textile workplaces, the air humidity is usually close to saturation. Frontline workers perform physically demanding work, which will make the body sweat greatly and increase the occurrence of heat-related illnesses. The microenvironment under clothing can be improved by a ventilation cooling vest with pressurized air (denoted VCV), and the trunk skin temperature will be decreased. However, the amount of heat that a VCV removes from a working human body in hot and humid environments is unclear. In this study, human experiments were carried out, the ambient temperature was controlled at 30 °C, 32 °C or 34 °C, and the air humidity was 90%. The subjects wore a labor suit (denoted LS) or a VCV, running on a treadmill at 5 km/h or 7.5 km/h. The results showed that the total trunk heat loss was increased by 169–237%, and the cooling power of the VCV was between 79.5 and 97.6 W when wearing the VCV. However, the actual skin wettedness is often less than the calculated value, and the calculated cooling power should be considered the upper limit. The study indicated that the cooling capacity of the VCV increased as the ambient temperature and labor intensity increased, and the heat dissipation of the body also increased.     

地震前后基准站GPS数据异常提取算法

目前对地震前兆异常的研究主要集中在“热”和“电”等方面,很少涉及基准站的GPS数据。然而,已经有学者证明震中附近基准站的GPS时间序列坐标数据中也蕴含着大地震的前兆信息。针对2001~2010年间美国本土发生的具有代表性的三个地震进行了研究,首次将Martingale理论运用于GPS数据处理,提出一种异常提取算法,进而对地震前后,震中附近多个基准站的GPS数据进行分析。实验结果表明算法能够有效的反映大地震前后GPS数据中异常的变化趋势,为使用GPS数据对大地震进行预报提供了更多可能。     

Spatial updating of objects after rotational and translational body movements in virtual environments

Spatial reasoning in architectural design can be better understood by considering the factors that affect the spatial updating process of the individual in an environment. This study focuses on the issue of spatial updating of viewed and imagined objects after rotational and translational body movements in a virtual environment (VE). Rotational and translational movements based on an egocentric frame of reference where there is no control of the user are compared in a desktop VE. Moreover, preference in architectural drawing medium and gender are analyzed as the factors that affect the spatial updating of objects in each body movement type. The results indicated that translational movement was more efficient than the rotational movement in judgment of relative directions in viewed objects. Furthermore, the viewed objects were more correctly spatially updated than the imagined ones both in translational and rotational body movements. In comparison of hand, computer and both as the drawing media, findings indicated that preference in computer medium in architectural design drawings was an effective one in spatial updating process in a VE. Contrary to the previous studies, it is found that there was no significant difference between gender and movement types.     

Posture,muscle activity and muscle fatigue in prolonged VDT work at different screen height settings

With the increasing use of video display terminals (VDTs), there is growing concern over the corresponding increase in the number of health problems reported. Although much research has focused on identifying the optimal screen height, there is to date no consensus. This study aimed to investigate the effect of prolonged (89 min) VDT work at four different screen heights on head-neck posture, muscle activity and the development of muscle fatigue. The results show that lowering screen height, starting from 15 cm above the baseline (i.e. top of the screen level with eye height while sitting), decreased the ear-eye angle, increased the viewing angle, increased the viewing angle relative to the ear-eye line, and increased the muscle activity of the neck extensor muscles. There were also some significant time effects on postural angles and muscle activity. In this study there were only rare occurrences of muscle fatigue, defined as a simultaneous increase in EMG amplitude and a shift of the EMG power spectrum to lower frequencies. Muscle activity increased significantly in some muscles and for certain screen heights.     

The relationship between class size and online activity patterns in asynchronous computer conferencing environments

This study analyzes the relationship between class size and student online activity patterns in a series of 28 graduate level computer conferencing courses. Quantitative analyses of note production, average note size, note opening and note reading percentages found a significant positive correlation between class size and mean number of notes generated. Significant negative correlations were found between class size and average note size and between class size and percent of notes opened. Analyses of average reading speeds among large classes and small classes revealed that students in large classes were more likely to scan lengthy notes (i.e., notes that contain more than 350 words). Possible explanations for these results are discussed.     

Nursing staff's communication modes in patient transfer before and after an educational intervention

The objective was to explore and describe nursing staff's body awareness and communication in patient transfers and evaluate any changes made after an educational intervention to promote staff competence in guiding patients to move independently. In total, 63 nursing staff from two hospitals wrote weekly notes before and after the intervention. The topics were: A) reflect on a transfer during the last week that you consider was good and one that was poor; B) reflect on how your body felt during a good and a poor transfer. The notes were analysed with content analysis. The results showed five different communication modes connected with nursing staff's physical and verbal communication. These communication modes changed after 1 year to a more verbal communication, focusing on the patient's mobility. The use of instructions indicated a new or different understanding of patient transfer, which may contribute to a development of nursing staff's competence.

Statement of Relevance: The present findings indicate that patient transfer consists of communication. Therefore, verbal and bodily communication can have an integral part of training in patient transfer; furthermore, the educational design of such programmes is important to reach the goal of developing new understanding and enhancing nursing staff's competence in patient transfer.     

Exploring activity theory as a tool for evaluating interactivity and learning in virtual environments for children

This paper explores the use of Activity Theory for the evaluation of user behaviour in immersive virtual environments. Specifically, the study of user behaviour focuses on interactivity, which is argued to be one of the most important processes that take place between a user and the system in virtual reality. The ultimate intention is to study the role and the effect of interactivity on learning and conceptual change and to examine how interaction and conceptual learning are related in the context of virtual environments developed primarily for informal educational settings. As a first step to this study, a set of exploratory experiments was carried out with children aged 7–12. The children were asked to complete tasks, such as the assembly of ancient columns from parts, which were designed to promote constructivist learning and explore the methods of carrying out in-depth experiments with children. This paper describes the analysis of these exploratory case studies from an Activity Theory perspective.

Composing and scheduling service‐oriented applications in time‐triggered distributed real‐time Java environments

During the last decade, the number of distributed application domains with temporal requirements has significantly augmented, arising the necessity of exploring new concepts and paradigms that allow, on the one hand, the development of dynamic and flexible distributed applications and, on the other hand, the reusability of code. Service‐oriented paradigms have been successfully applied to distributed environments, increasing their flexibility and allowing the reusability of their components. Besides, distributed real‐time Java technologies have shown to be a good candidate to deploy real‐time distributed applications. This paper presents a model for service‐oriented applications on a time‐triggered distributed real‐time Java environment, focusing on the definition of the temporal model of an application and its schedulability, applying and evaluating this model in real‐time service‐oriented composition algorithms. Copyright © 2012 John Wiley & Sons, Ltd.     

Web mining and privacy concerns: Some important legal issues to be consider before applying any data and information extraction technique in web-based environments

Web mining is a concept that gathers all techniques, methods and algorithms used to extract information and knowledge from data originating on the web (web data). A part of this technique aims to analyze the behavior of users in order to continuously improve both the structure and content of visited web sites. Behind this quite altruistic belief – namely, to help the user feel comfortable when they visit a site through a personalization process – there underlie a series of processing methodologies which operate at least arguably from the point of view of the users’ privacy.Thus, an important question arises; to what extent may the desire to improve the services offered through a web site infringe upon the privacy of those who visit it? The use of powerful processing tools such as those provided by web mining may threaten users’ privacy.Current legal scholarship on privacy issues suggests a flexible approach that enables the determination, within each particular context, of those behaviors that can threaten individual privacy. However, it has been observed that TIC professionals, with the purpose of formulating practical rules on this matter, have a very narrow-minded concept of privacy, primarily centered on the dichotomy between personal identifiable information (PII) and anonymous data.The aim of this paper is to adopt an integrative approach based on the distinctive attributes of web mining in order to determine which techniques and uses are harmful.     

Avoiding chaotic use of social media before,during, and after emergencies: Design and evaluation of citizens’ guidelines

Social media have been established in many natural disasters or human‐induced crises and emergencies. Nowadays, authorities, such as emergency services, and citizens engage with social media in different phases of the emergency management cycle. However, as research in crisis informatics highlights, one remaining issue constitutes the chaotic use of social media by citizens during emergencies, which has the potential to increase the complexity of tasks, uncertainty, and pressure for emergency services. To counter these risks, besides implementing supportive technology, social media guidelines may help putting artefact and theoretical contributions into practical use for authorities and citizens. This paper presents the design and evaluation (with 1,024 participants) of citizens’ guidelines for using social media before, during, and after emergencies.     

A shirt containing multistage phase change material and active cooling components was associated with increased exercise capacity in a hot,humid environment

Recent advances in clothing design include the incorporation of phase change materials (PCM) and other active cooling components (ACC) to provide better body heat dissipation. The purpose of this study was to determine the effect of wearing a shirt containing multistage PCM/ACC on exercise capacity at low (5.0), moderate–high (7.5) and extreme (9.0) levels of the physiological strain index (PSI). Fourteen individuals tested two shirts (control vs. cooling) during 45-min of interval running in a hot, humid (35 ± 1 °C; 55 ± 6% RH) environment. The cooling shirt resulted in an 8% improvement in exercise capacity at a PSI of 7.5 (p < 0.05). The observed increase in exercise capacity would likely translate to a significant improvement in exercise performance. More research is needed to determine a best practice approach for the use of cooling clothing as a counter to exercise-induced heat exposure.

Practitioner Summary: In this report, we demonstrate that when forced to exercise in a hot, humid environment, an individual’s exercise capacity may increase by as much as 8% when wearing a shirt composed of multistage phase change material and active cooling components.     

Musculoskeletal, visual and psychosocial stress in VDU operators before and after multidisciplinary ergonomic interventions. A 6 years prospective study—Part II

A prospective epidemiological field study covering a 2 years period has earlier been published (Appl. Ergon. (1998) 29(5) 335). The study has a parallel group design with two intervention groups (T and S) and one control group (C) of Visual Display Unit (VDU) operators. The present paper covers the period from 2 to 6 years of the study. After 3.5 years, the C group got the same intervention in terms of new lighting system, new workplaces and at last an optometric examination and corrections if needed. The C group reported a significant reduction in visual discomfort after interventions while the two groups (T and S) continued to report significant reduction of visual discomfort after 6 years. By supporting the forearm on the table top, the C group reported significant reduction of shoulder and neck pain while the T group reported significant reduction in shoulder and back pain after 6 years. Organizational and psychosocial factors at work and outside work did not show any significant changes during the study period.