Our ancestral physiological phenotype: an adaptation for hypoxia tolerance and for endurance performance?

There are well known mechanistic similarities in human physiology between adaptations for endurance performance and hypoxia tolerance. By using background principles arising from recent studies of the evolution of the diving response in marine mammals, here we analyze human responses to hypobaric hypoxia based on studies with several different low and high altitude human lineages. As in the evolution of the diving response in pinnipeds, we found "conservative" and "adaptable" physiological characters involved in human responses to hypoxia. Because the analysis concerns traits within a single species, conservative characters dominate the picture (they define basic human physiology and largely are independent of environmental parameters). Most notably, we also found evidence for adaptable characters forming the foundations for a fairly unique physiological phenotype-a low capacity version favored under hypobaric hypoxia and a high capacity one favored for endurance performance. Because current evidence implies that the human species arose under conditions that were getting colder, drier, and higher (situations in which these traits would have been advantageous), we hypothesize that this physiology is our "ancestral" condition.     

Genetics and the pathobiology of ageing

Genetics offers a powerful approach to the elucidation of mechanisms underlying specific components of the senescent phenotype of our species. Perhaps thousands of gene variations have escaped the force of natural selection and thus play roles in the genesis of different patterns of ageing in man. It is possible that a subset of these genes may be of particular importance in how most people age. While variations at the Werner helicase locus could be one such example, several lines of evidence suggest that mutation at that locus leads to a 'private' mechanism of ageing. It will be important, however, to investigate polymorphisms underlying the regulation of expression of this gene in the general population. Polymorphisms (normally occurring variants of a gene, or sequence of DNA), rather than mutations, may also prove to be more relevant to our understanding of the differing susceptibilities of people to common disorders such as late onset Alzheimer's disease. Polymorphic forms of the Apolipoprotein E gene is a good example. It remains to be seen if the pathogenetic framework (beta amyloidosis) derived from studies of the several rare mutations responsible for early onset familial forms of the disease proves relevant to the pathogenesis of the vastly more prevalent sporadic forms of the disorder. In contrast to the satisfying progress on the genetics of the diseases of ageing, research on the genetic basis for unusually robust retention of structure and function in old age has been neglected and requires a higher priority for the future. Such research should include studies of environmental agents and should address mechanisms of 'sageing', a stage in the life course characterized by an extensive utilization of behavioural and physiological adaptations to compensate for functional declines. For the genetics of longevity, we have to turn to genetically tractable organisms such as nematodes and fruit flies. Such studies have provided significant support for the oxidative stress theory of ageing. It will be important to learn more about the age-related pathologies and pathophysiologies of these organisms.     

Expert performance: Its structure and acquisition.

Counter to the common belief that expert performance reflects innate abilities and capacities, recent research in different domains of expertise has shown that expert performance is predominantly mediated by acquired complex skills and physiological adaptations. For elite performers, supervised practice starts at very young ages and is maintained at high daily levels for more than a decade. The effects of extended deliberate practice are more far-reaching than is commonly believed. Performers can acquire skills that circumvent basic limits on working memory capacity and sequential processing. Deliberate practice can also lead to anatomical changes resulting from adaptations to intense physical activity. The study of expert performance has important implications for our understanding of the structure and limits of human adaptation and optimal learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of physical exertion on task performance in modern manufacturing: a taxonomy, a review, and a model

Modern manufacturing systems have the characteristic of demanding human cognitive task performance in an environment where sudden physical demands are also possible. There is little research addressing the effects of physical work on cognitive task performance and it is not well organized for application to manufacturing systems design. This paper uses an initial three-dimensional taxonomy to review the literature. Some clear findings emerge, but many studies produced contradictory results. While part of the contradiction was due to experimental technique, some was also due to the lack of a detailed structure to guide future research. Such a model is thus proposed, using the concept of limited resources for both the cognitive and physical aspects of tasks. In addition, specific predictions of research needs for modern manufacturing systems arise.     

Physical fitness training and mental health.

Reviews theory and research that have attempted to relate fitness training to improvements on psychological variables among normals as well as selected clinical populations. Theoretical speculations in this area are critiqued, and research designs are evaluated as either experimental or quasi-experimental and therefore interpretable, or preexperimental and therefore largely uninterpretable. The research suggests that physical fitness training leads to improved mood, self-concept, and work behavior; the evidence is less clear as to its effects on cognitive functioning, although it does appear to bolster cognitive performance during and after physical stress. Except for self-concept, personality traits are not affected by improvements in physical fitness. Mentally retarded children demonstrate psychological improvement following physical fitness training, but no conclusion can be reached regarding the effects of physical fitness training with other clinical syndromes. (2? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The systemic integration of human functions: new approaches to the diagnosis and correction of stressor states

The paper provides evidence for a new principle of the systemic organization of human functions. Instead of the concepts of man as a set of organs which are bound up with nervous and humoral regulation, the author considers on the basis of the functional systems theory the human body as a total combination of various interacting systems of different levels of organizations, each yields body's useful adaptive responses on the principles of multiparametric and successive interactions with other functional systems. The paper reveals the principles of interaction of functional systems in the whole organism. Problems in the evaluation of human physiological functions in the place of work, systemic principles of detection of stress states and their rehabilitation are considered in the context of functional systems.     

Impact of Stress on the Performance of Construction Project Managers

The work of construction project managers (CPMs) is often highly stressful, due to time pressures, and due to the uncertainties and the dynamic social structure involved in construction projects. This study aims to investigate the impact of stress on the performance of CPMs. Correlation analysis and structural equation modeling are employed to uncover the relationships between different types of stress (i.e., objective stress, burnout, and physiological stress) and the work performances (i.e., task performance, interpersonal performance, and organizational performance) of CPMs. Data were collected from 108 CPMs who work in a variety of construction sectors, including prime contractors, subcontractors, developers, consultant firms, and the public sector. Results showed that (1) objective stress reduces the task performance of CPMs while burnout can have a positive effect on it; (2) interpersonal performance is maximized with a moderate level of objective stress (i.e., an inverted-U-shaped relationship between these two variables) and increases in line with the improvement of the task performance of individuals; and (3) organizational performance has U-shaped relationships with both burnout and physiological stresses and is worsened by objective stress. Last, it is suggested to stakeholders that regular reviews of job allocation, stress appraisals, stress management workshops, group or individual counseling, and psychological treatment or physiotherapy be carried out to optimize the stress and the performance of CPMs.     

Metabolic reserves and evolved stress resistance in Drosophila melanogaster

We have examined starvation and desiccation resistance in 43 outbred populations of Drosophila melanogaster that have diverged from a common ancestral population as a result of a variety of defined selection protocols. The populations differ up to 8.5-fold in desiccation resistance and up to 10-fold in starvation resistance. We used these populations to search for evolved physiological changes that might explain the differences in stress resistance. We examined two hypotheses for increased stress resistance that had been proposed previously in the literature: (1) that increments in starvation resistance are principally the result of differential lipid accumulation, and (2) that changes in glycogen accumulation play a role in evolved increases in resistance to desiccation stress. By quantifying desiccation resistance, starvation resistance, lipid content, and carbohydrate content in each of our populations of flies, we were able to demonstrate strong correlations between the capacity of the flies to resist starvation and the quantity of lipid or carbohydrate that the flies had stored. The strongest correlation (R2 = 0.99) was observed when the total energy content of both the lipid and carbohydrate stores was regressed against starvation resistance. These results demonstrate that the flies responded to selection for starvation resistance through a genetically determined increase in both lipid and carbohydrate storage. Similar analyses of the correlation between lipid storage or total energy storage and desiccation resistance revealed no significant correlations. Carbohydrate storage was significantly correlated with desiccation resistance in female but not in male flies. These results suggest that different forms of stress are resisted with distinct physiological mechanisms and that the evolutionary response of the flies to stress selection is specific to the stress imposed.     

Review of Depression in the medically ill: An integrated approach.

Reviews the book, Depression in the medically ill: An integrated approach by G. Rodin, J. Craven, and C. Littlefield (see record 1991-97973-000). This book provides an in-depth coverage of current issues in the management of depression in the medically ill. The book is balanced in theoretical perspective and quite comprehensive in coverage of the empirical literature. The authors are well known to the area of depression and physical illness. The book is organized into three main sections dealing with 1) Clinical Presentation, 2) Etiology and Pathogenesis, and 3) Treatment. Numerous case examples are provided throughout to highlight different aspects of symptom presentation, diagnostic problems, and therapeutic management. Notably lacking from the review of prevalence studies is the work examining depression and chronic pain populations. In sum, Rodin et al. have drawn on a vast literature to provide a clear and coherent picture of the current state of knowledge and theory dealing with depression and medical illness. Their book joins a number of recent papers attempting to draw more attention to clinical issues in the management of depression in the medically ill. I would recommend the book to all clinicians who work with medically ill populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of Temperature on Tensile Stress–Strain and Work Hardening Behaviour of Forged Thick Section?9Cr–1Mo Ferritic Steel

True stress (??)?Ctrue plastic strain (??) behaviour examined for temperatures ranging from 300 to 873?K suggested that a combination of Ludwigson and Hollomon equations describes ??C?? behaviour most accurately in forged thick section?9Cr?C1Mo steel. Alternatively, the flow behaviour for temperature range 300?C873?K can be described adequately using single Voce equation. Good correlations have been obtained between work hardening parameters evaluated using Voce equation and the respective tensile properties. The variations of instantaneous work hardening rate (???=?d??/d??) and ??? with stress displayed two-stage behaviour characterised by a rapid decrease at low stresses (transient stage) followed by a gradual decrease at high stresses (stage-III). The variations of work hardening parameters, ?? versus ?? and ??? versus ?? with temperature exhibited three distinct temperature regimes along with signatures of dynamic strain ageing at intermediate temperatures and dominance of dynamic recovery at high temperatures. Comparison of work hardening parameters obtained using Voce equation and Kocks?CMecking approach suggested an analogy between the two for the steel.     

The nitric oxide pathway in pre-eclampsia: pathophysiological implications

Ageing constitutes a risk factor for magnesium deficit. Primary magnesium deficit originates from two etiological mechanisms: deficiency and depletion. Primary magnesium deficiency is due to insufficient magnesium intake. Dietary amounts of magnesium are marginal in the whole population whatever the age. Nutritional deficiencies are more pronounced in institutionalized than in free-living ageing groups. Primary magnesium depletion is due to dysregulation of factors controlling magnesium status: intestinal magnesium hypoabsorption, reduced magnesium bone uptake and mobilisation, sometimes urinary leakage, hyperadrenoglucocorticism by decreased adaptability to stress, insulin-resistance and adrenergic hyporeceptivity. Secondary magnesium deficit in ageing largely results from various pathologies and treatments common to elderly persons: i.e. non insulin dependent diabetes mellitus and use of hypermagnesuric diuretics. Magnesium deficit may participate in the clinical pattern of ageing: mainly neuromuscular, cardiovascular and renal symptomatologies. The consequences of hyperadrenoglucocorticism--whose non response to dexamethasone suppression test appears the simplest marker--may concern immunosuppression, muscle atrophy, centralization of fat mass, osteoporosis, hyperglycemia, hyperlipidemia, atherosclerosis, disturbances in mood and mental performances through accelerated hippocampal ageing particularly. Treatment of magnesium deficiency requires simple oral physiological magnesium supplementation. Treatment of the different types of magnesium depletion leads to a more or less specific control of pathophysiological disturbances of the required magnesium substrate. Open and double blind studies on the effects of the treatments of magnesium deficiency and of magnesium depletions in geriatic populations are too scarce. Further study is necessary to assess the accurate place of magnesium deficit in the physiopathology of ageing.     

Circadian patterns of ischemic events

These is evidence of circadian variations in the occurrence of ischemic events such as: silent myocardial ischemia, stable angina, instable angina, acute myocardial infarction, sustained ventricular tachycardia, cerebral infarction, transient ischemic attack (TIA) and sudden cardiac death. In the general population many cardiovascular disorders occur with the greatest frequency between 6 and 12 a.m. (i.e. after awakening). Blood pressure, too, follows a distinct circadian pattern. Factors affecting circadian variations in cardiovascular disorders include physiological determinants, such as heart rate, catecholamine release, and platelet aggregation-which themselves cyclically vary-, and exogenous factors such as mental stress, anxiety, and physical activity. In chronotherapy, circadian variations in disease states and in the pharmacodynamic properties of drugs are exploited to improve prevention and treatment. Characterization of diseases states with this approach allows more accurate determination of the times when patients are at highest risk and therefore in greatest need of preventive measures; it also provides a mechanism for designing optimal drug regimens. In this review we therefore describe recent findings about the effects of biorhythms on cardiovascular disorders and their implications for optimal drug therapy.     

Unlocking the black box: Exploring the link between high-performance work systems and performance.

With a growing body of literature linking systems of high-performance work practices to organizational performance outcomes, recent research has pushed for examinations of the underlying mechanisms that enable this connection. In this study, based on a large sample of Welsh public-sector employees, we explored the role of several individual-level attitudinal factors—job satisfaction, organizational commitment, and psychological empowerment—as well as organizational citizenship behaviors that have the potential to provide insights into how human resource systems influence the performance of organizational units. The results support a unit-level path model, such that department-level, high-performance work system utilization is associated with enhanced levels of job satisfaction, organizational commitment, and psychological empowerment. In turn, these attitudinal variables were found to be positively linked to enhanced organizational citizenship behaviors, which are further related to a second-order construct measuring departmental performance. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The scientific trends and tasks in occupational physiology today

Evaluating a human during occupational activities, occupational physiology should put emphasis on two principal and cooperated directions. Those are aimed to minimize occupational risk, preservation of working capacity, long occupational life and human health. The first direction is associated with theoretic and practical work on differential diagnosis of various functional systems: regulation of working strain, fatigue and tension. Work in this direction helps to solve such practical problems as rehabilitation and assessment of human resources, evaluation of occupational stress, design of automated monitoring systems, etc. The second direction covers hygienic regulation of occupational factors. Their intensity and duration should be assessed with consideration of age, personality and other traits of a worker. In addition, combined action of existing hazards and the new ones should be considered in formation of regulatory technology documents.     

The effects of stress on memory and the hippocampus throughout the life cycle: implications for childhood development and aging

Studies in animals showing hippocampal atrophy and associated memory deficits in stress and aging have implications for stress and aging in humans. Clinical studies in traumatized human populations with posttraumatic stress disorder (PTSD) have replicated studies in animals, showing reduction in volume of the hippocampus measured with magnetic resonance imaging and associated memory deficits. Trauma at different stages of development (early childhood abuse versus trauma in later life due to combat) may influence the nature of memory deficits and hippocampal atrophy. Studies in aging human subjects are consistent with animal studies, although future research is needed in this area. The similarities between biological findings related to cortisol and the hippocampus in stress and aging in both animal and human studies raises the question of whether PTSD can be seen as a form of accelerated aging. Evidence that stress affects the hippocampus and the capacity for learning has broad implications for public health policy, underlying the need for additional resources in this important area and a reexamination of our understanding of factors influencing academic achievement.     

Impacts of Stressors and Stress on the Injury Incidents of Construction Workers in Hong Kong

Construction workers (CWs) are the key and indispensable contributors to every construction project. Their psychological feelings greatly influence their behaviors and safety performance. To improve CWs’ safety performance in dangerous working environment, the current research aims to identify the various stressors affecting two types of stress of CWs (i.e., job stress and emotional stress) and to explore the impacts of the two types of stress on CW injury incidents in Hong Kong. Eleven stressors were identified through factor analysis: work overload, role ambiguity, lack of autonomy, unfair reward and treatment, appropriate safety equipment, optimism, interrole conflict, poor workgroup relationship, lack of feedback, poor physical environment, and unsafe environment. The results of correlation and regression analyses reveal that (1) among the two types of stress identified, injury incident of CWs was found to be affected by emotional stress only, (2) emotional stress is predicted by work overload, interrole conflict, poor physical environment, unfair reward and treatment, and appropriate safety equipments, and (3) poor workgroup relationship, work overload, and interrole conflict predict job stress of CWs. Based on the result, various recommendations are suggested to employers on how to minimize CW injury incidents.     

Giving voice to silence: The psychologist as witness.

An analysis of how personal and professional factors have interacted to determine the author's career path provides the backdrop against which alternative constructions of psychological science and practice are presented. The author presents examples from her work that illustrate possibilities for a science and practice of psychology that respond to the variations in human experience as the norm rather than as deviations from it. Specific areas that need further exploration in order to make psychology more responsive to the needs of all populations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Turbulent Stresses and Secondary Currents in a Tidal-Forced Channel with Significant Curvature and Asymmetric Bed Forms

Acoustic Doppler current profilers are deployed to measure both the mean flow and turbulent properties in a channel with significant curvature. Direct measurements of the Reynolds stress show a significant asymmetry over the tidal cycle where stresses are enhanced during the flood tide and less prominent over the ebb tide. This asymmetry is corroborated by logarithmic fits using 10?min averaged velocity data. A smaller yet similar tendency asymmetry in drag coefficient is inferred by fitting the velocity and estimated large-scale pressure gradient to a one-dimensional along-channel momentum balance. This smaller asymmetry is consistent with recent modeling work simulating regional flows in the vicinity of the study site. The asymmetry in drag suggests the importance of previously reported bed forms for this channel and demonstrates spatial and temporarily variations in bed stress. Secondary circulation patterns observed in a relatively straight section of channel appear driven by local curvature rather than being remotely forced by the regions of significant curvature only a few hundred meters from the measurement site.     

Roles of human factors and ergonomics in meeting the challenge of terrorism.

Human factors and ergonomics research focuses on questions pertaining to the design of devices, systems, and procedures with the goal of making sure that they are well suited to human use and focuses on studies of the interaction of people with simple and complex systems and machines. Problem areas studied include the allocation of function to people and machines, person–system interface design, accident prevention, risk assessment, human performance under various types of stress, crisis management, search and rescue operations, decision aiding, the training and coordination of teams, and negotiation and conflict resolution, among many others. Much human factors and ergonomics work has been directed at responding to accidents (train wrecks, airplane crashes, nuclear plant mishaps) and natural disasters (hurricanes, earthquakes, floods). Although most of this work has not been motivated by the reality of terrorism or, in particular, by the attacks of 9/11, much of it is relevant to one or another aspect of terrorism in its various manifestations, and human factors and ergonomics researchers are increasingly making the connection. The purpose of this article is to illustrate this relevance by noting a few studies, from among the many that could be cited, that have implications for helping to prevent terrorism or for dealing with the effects of terrorist incidents when they occur. (PsycINFO Database Record (c) 2011 APA, all rights reserved)