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PubMed1996

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.

Attention↗

PubMed2000

Children's physical activity and physical self-perceptions.

The aim of this study was to determine the relationship between physical self-perceptions and physical activity in Canadian school children aged 10-14 years. The sample consisted of 220 boys and 246 girls in grades 5-8. Physical activity was assessed by 7-day recall using the Physical Activity Questionnaire for Older Children. Self-perceptions of physical conditioning, sports competence, strength, body appearance and general physical self-worth were measured by the Physical Self-Perception Profile (PSPP). We found that boys were more physically active than girls and had higher perceptions of sport competence and strength. All PSPP scales were significantly correlated with physical activity in both boys and girls. Structural equation modelling procedures found the hierarchical PSPP model provided a good fit to the observed data, with little evidence of differences between the sexes. Analysis of five alternative structural models of the relationship between the PSPP and physical activity found the most parsimonious model to have significant pathways from both physical conditioning and sport skills to physical activity. Models for the sample as a whole, for boys and for girls were similar, accounting for an R2 of 0.27-0.29 for physical activity. Our results demonstrate that physical self-perceptions, especially physical conditioning and sport skills, are significant correlates of activity in this population.

Child↗

PubMed1999

Childhood maltreatment increases risk for personality disorders during early adulthood.

BACKGROUND: Data from a community-based longitudinal study were used to investigate whether childhood abuse and neglect increases risk for personality disorders (PDs) during early adulthood. METHODS: Psychosocial and psychiatric interviews were administered to a representative community sample of 639 youths and their mothers from 2 counties in the state of New York in 1975, 1983, 1985 to 1986, and 1991 to 1993. Evidence of childhood physical abuse, sexual abuse, and neglect was obtained from New York State records and from offspring self-reports in 1991 to 1993 when they were young adults. Offspring PDs were assessed in 1991 to 1993. RESULTS: Persons with documented childhood abuse or neglect were more than 4 times as likely as those who were not abused or neglected to be diagnosed with PDs during early adulthood after age, parental education, and parental psychiatric disorders were controlled statistically. Childhood physical abuse, sexual abuse, and neglect were each associated with elevated PD symptom levels during early adulthood after other types of childhood maltreatment were controlled statistically. Of the 12 categories of DSM-IV PD symptoms, 10 were associated with childhood abuse or neglect. Different types of childhood maltreatment were associated with symptoms of specific PDs during early adulthood. CONCLUSIONS: Persons in the community who have experienced childhood abuse or neglect are considerably more likely than those who were not abused or neglected to have PDs and elevated PD symptom levels during early adulthood. Childhood abuse and neglect may contribute to the onset of some PDs.

Adolescent↗

PubMed2000

Monte Carlo dose calculations and radiobiological modelling: analysis of the effect of the statistical noise of the dose distribution on the probability of tumour control.

The aim of this work is to investigate the influence of the statistical fluctuations of Monte Carlo (MC) dose distributions on the dose volume histograms (DVHs) and radiobiological models, in particular the Poisson model for tumour control probability (tcp). The MC matrix is characterized by a mean dose in each scoring voxel, d, and a statistical error on the mean dose, sigma(d); whilst the quantities d and sigma(d) depend on many statistical and physical parameters, here we consider only their dependence on the phantom voxel size and the number of histories from the radiation source. Dose distributions from high-energy photon beams have been analysed. It has been found that the DVH broadens when increasing the statistical noise of the dose distribution, and the tcp calculation systematically underestimates the real tumour control value, defined here as the value of tumour control when the statistical error of the dose distribution tends to zero. When increasing the number of energy deposition events, either by increasing the voxel dimensions or increasing the number of histories from the source, the DVH broadening decreases and tcp converges to the 'correct' value. It is shown that the underestimation of the tcp due to the noise in the dose distribution depends on the degree of heterogeneity of the radiobiological parameters over the population; in particular this error decreases with increasing the biological heterogeneity, whereas it becomes significant in the hypothesis of a radiosensitivity assay for single patients, or for subgroups of patients. It has been found, for example, that when the voxel dimension is changed from a cube with sides of 0.5 cm to a cube with sides of 0.25 cm (with a fixed number of histories of 10(8) from the source), the systematic error in the tcp calculation is about 75% in the homogeneous hypothesis, and it decreases to a minimum value of about 15% in a case of high radiobiological heterogeneity. The possibility of using the error on the tcp to decide how many histories to run for a given voxel size is also discussed.

Computer Simulation↗

PubMedDate not supplied

On the aggregation state and QSPR models. The solubility of herbicides as a case study.

The goal of this article is to stress the importance of considering the phase in QSPR studies. It is found that the phase plays a fundamental role in the QSPR models from both a statistical and a physical point of view. From a statistical point of view, it is observed that the predictive performance drops drastically when the QSPR model, obtained for a given phase, is used to predict the solubility of the same set of compounds but in another phase. From a physical point of view, when the compounds in the training set are in different phases, the physical interpretation of the descriptors involved in the model is obscured because the descriptors which appear in the correlation equation are a sort of average encoding the different physical mechanisms underlying the property. It is shown that the use of compounds in the same phase, instead, allows a more transparent physical interpretation of the descriptors involved in the model and, at the same time, improves the statistics of the models.

Herbicides↗

PubMedDate not supplied

Quantitation in positron emission computed tomography: 7. A technique to reduce noise in accidental coincidence measurements and coincidence efficiency calibration.

A method of processing accidental coincidence events (AC) and detector efficiency (DE) calibration data, which reduces the statistical noise in these measurements, and, consequently, reduces the noise in positron emission tomographic images using the technique, is described. The technique uses the fact that, in these measurements with N detectors in coincidence with N other detectors, N2 values of ACs or DEs are measured. However, these values are composed of only 2N components, which are either singles rates or individual DEs. The full set of data is used to implicitly solve for these values and the individual ACs or DEs recalculated with an improvement in statistical error equivalent to an N2/(2N + 1) increase in accumulated events for the case of a uniform distribution. This result was verified experimentally.

Electricity↗

PubMed1983

Depression as a powerful discriminator between physically active and sedentary middle-aged men.

This study identifies the relative importance of psychological dimensions that discriminate between habitually physically active and sedentary men. The data support the notion that physical activity has psychological benefits. Subjects (N = 22) were normal, medically healthy middle-aged men (40-60 years of age). Data were collected on selected physiological (treadmill) and psychological (MMPI) variables and replicated within four months. The Student's t-test and discriminant function analysis were used in the statistical analysis. Physically active men (n = 11) have lower depression (scale 2) and lower social introversion (scale 10) than the sedentary men (n = 11). The physically active men may exhibit MMPI scale differences in 'neurotic' tendencies from the sedentary men, but there is no apparent difference in scales suggestive of 'psychotic' tendencies. Depression (scale 2) is the most powerful discriminator between physically active and sedentary men, followed by hysteria (scale 3) and social introversion (scale 10). In conclusion, our data identify depression as the most important MMPI scale that discriminates between physically active and sedentary men.

Adult↗

PubMed2001

Phase field model for three-dimensional dendritic growth with fluid flow.

We study the effect of fluid flow on three-dimensional (3D) dendrite growth using a phase-field model on an adaptive finite-element grid. In order to simulate 3D fluid flow, we use an averaging method for the flow problem coupled to the phase-field method and the semi-implicit approximated projection method (SIAPM). We describe a parallel implementation for the algorithm, using the CHARM++ FEM framework, and demonstrate its efficiency. We introduce an improved method for extracting dendrite tip position and tip radius, facilitating accurate comparison to theory. We benchmark our results for 2D dendrite growth with solvability theory and previous results, finding them to be in good agreement. The physics of dendritic growth with fluid flow in three dimensions is very different from that in two dimensions, and we discuss the origin of this behavior.

Algorithms↗

PubMed2002

Physiological and psychological influences on postoperative fatigue.

UNLABELLED: Fatigue is common after major surgery and delays recovery. We studied the role of physiological and psychological factors in determining fatigue and physical well being after surgery in 102 patients undergoing primary hip arthroplasty. Self-administered questionnaires were used to measure the intensity of feelings of fatigue, vigor, depression, and subjective physical well being on the day before surgery, on the third and seventh postoperative days, and 1 and 6 mo after surgery. The physiological response to surgery was determined by sequential measurements of circulating norepinephrine, epinephrine, cortisol, interleukin-6, and C-reactive protein during the 7 days after surgery. The peak value of each variable was used for statistical analysis. Physical well being decreased significantly at 3 and 7 days but increased significantly at 1 and 6 mo. Fatigue decreased significantly at 1 and 6 mo. Multiple regression analysis showed that the main predictor of worse physical well being at 3 days was the size of the C-reactive protein response. Subsequently, the main predictor was the level of preoperative well being. The severity of fatigue and vigor after surgery were predicted mostly by the preoperative levels of the respective variable. We conclude that fatigue after hip arthroplasty was not predicted by physiological variables but was largely predicted by preoperative levels of fatigue. IMPLICATIONS: Fatigue is common after major surgery and delays recovery. It is usually attributed to the physiological response to surgery. We studied patients undergoing hip arthroplasty and found that the severity of postoperative fatigue was not predicted by physiological changes. Instead, it was predicted by the preoperative level of fatigue.

Adult↗

PubMed2001

Evaluation of docking functions for protein-ligand docking.

Docking functions are believed to be the essential component of docking algorithms. Both physically and statistically based functions have been proposed, but there is no consensus about their relative performances. Here, we propose an evaluation approach based on exhaustive enumeration of all possible docking solutions obtained with a discretized description of a rigid docking process. We apply the approach to study both molecular mechanics and statistical potentials. It is found that the statistical potential evaluated is less effective than the AMBER molecular mechanics function to provide an accurate description of the docking process when the exact experimental coordinates are used. However, when coordinates of crystal structures obtained with analogous ligands are used, similar performances are obtained in both cases. Possible reasons for the successes and failures of both docking schemes have been uncovered using linear discriminant analysis, on the basis of a set of physicochemical descriptors capturing the main physical effects at play during protein-ligand docking. In both types of potentials steric effects appear critical to obtain a successful docking. Our results also indicate that neglecting desolvation effects and the explicit treatment of hydrogen bonds are the main source of the failures observed with the molecular mechanics potential. On the other hand, detailed consideration of steric interactions, with a careful treatment of dispersive forces, seems to be needed when using statistical potentials derived from a structural database. The possibility of filtering combinatorial libraries in order to maximize the probability of correct docking is discussed.

Algorithms↗

PubMed2005

Snacking frequency in relation to energy intake and food choices in obese men and women compared to a reference population.

OBJECTIVE: To investigate snacking frequency in relation to energy intake and food choices, taking physical activity into account, in obese vs reference men and women. DESIGN: Cross-sectional, descriptive study. SUBJECTS: In total, 4259 obese, middle-aged subjects (1891 men and 2368 women) from the baseline examination of the XENDOS study and 1092 subjects (505 men and 587 women) from the SOS reference study were included. MEASUREMENTS: A meal pattern questionnaire describing habitual intake occasions (main meals, light meals/breakfast, snacks, drink-only), a dietary questionnaire describing habitual energy and macronutrient intake and a questionnaire assessing physical activity at work and during leisure time were used. RESULTS: The obese group consumed snacks more frequently compared to the reference group (P<0.001) and women more frequently than men (P<0.001). Energy intake increased with increasing snacking frequency, irrespective of physical activity. Statistically significant differences in trends were found for cakes/cookies, candies/chocolate and desserts for the relation between energy intake and snacking frequency, where energy intake increased more by snacking frequency in obese subjects than in reference subjects. CONCLUSION: Obese subjects were more frequent snackers than reference subjects and women were more frequent snackers than men. Snacks were positively related to energy intake, irrespective of physical activity. Sweet, fatty food groups were associated with snacking and contributed considerably to energy intake. Snacking needs to be considered in obesity treatment, prevention and general dietary recommendations.

Adult↗

PubMed2007

Body mass index and physical activity as risk factors for pancreatic cancer: the Multiethnic Cohort Study.

OBJECTIVE: To examine body mass index (BMI) and physical activity as risk factors for pancreatic cancer. METHODS: Eight-year prospective data from 77,255 men and 90,175 women including 237 and 235 pancreatic cancer cases, respectively, in the Hawaii-Los Angeles Multiethnic Cohort Study were analyzed. Participants completed a questionnaire that included questions on body weight, height, and physical activity. Cox proportional hazards models were calculated to estimate relative risks (RR) of pancreatic cancer by levels of BMI and total physical activity (as metabolic equivalents (METs)) adjusted for several potential confounders. RESULTS: Obesity (BMI > or = 30 kg/m(2)) was associated with an increased pancreatic cancer risk in men (RR = 1.51 (95% CI: 1.02-2.26)), but a reduced risk in women (RR = 0.65 (95% CI: 0.43-0.99)). In men the risk was higher in never smokers than in current or former smokers, though differences were not statistically significant. Physical activity was not associated with pancreatic cancer risk in either men or women. CONCLUSION: The findings suggest, that a BMI of > or = 30 kg/m(2) may be a risk factor for pancreatic cancer in men. No evidence of an effect of physical activity on risk was found.

Black or African American↗

PubMed1983

The impact of patients with nonorganic physical findings on a controlled trial of transcutaneous electrical nerve stimulation and electroacupuncture.

Fifty-four patients treated in a three-week in-patient rehabilitation program were randomly assigned to and accepted treatment with electroacupuncture (n = 17), TENS (low-intensity transcutaneous nerve stimulation, n = 18) and TENS-dead battery (placebo, n = 18). Outcome measures included estimates of pain (on a visual analogue scale) and disability by both physician and patient as well as physical measures of spine function. Two groups were constructed based on the absence of nonorganic physical findings (Valid group, n = 30) and the presence of two or more nonorganic physical findings out of a possible four (Invalid group, n = 10). Multivariate and univariate analyses of covariance were utilized to determine effects of treatment (acupuncture, TENS, placebo) and the effects of over-reporting (presence of excessive nonorganic physical findings). Statistically significant findings demonstrated that the acupuncture group enjoyed more relief of peak pain and more relief of pain on an average day at the three-month return assessment. Additionally, the acupuncture group demonstrated greater improvement in extension trunk strength at the discharge assessment. The Invalid group were found to have a contaminating effect on the acupuncture results. Analysis also demonstrated associations between nonorganic physical findings and both personality traits ("Conversion V" profile on MMPI) and retention of an attorney. Researchers conducting clinical trials in chronic low-back pain patients should control for contamination by the presence of over-reporters.

Acupuncture Therapy↗

PubMed1999

Mode of physical activity and self-efficacy in older adults: a latent growth curve analysis.

A randomized controlled trial examined the effect of two physical activity modes on changes in self-efficacy over the course of a 12-month period in older, formerly sedentary adults (N = 174, M age = 65.5 years). Participants were randomized into either an aerobic activity group or a stretching and toning group. Structural equation modeling was employed to conduct multiple sample latent growth curve analyses of individual growth in exercise and physical self-efficacy over time. Results revealed a curvilinear growth pattern for both types of efficacy with increases occurring over the first 6 months followed by declines at the 6-month follow-up. There was a significant treatment by mean level growth interaction for exercise efficacy with both groups increasing over time, but the aerobic group evidenced a twofold increase in growth over the stretching group. Structural analyses indicated that frequency of exercise participation was a significant predictor of overall growth in efficacy, and improvements in fitness were only related to exercise efficacy growth in the stretching group. Findings are discussed in terms of social cognitive theory and further application of latent growth curve modeling to studies of physical activity effects in older adults.

Activities of Daily Living↗

PubMed1995

Determination of supply and requirements in physical therapy: some considerations and examples.

This article is an exploration of the specific application of need-based and demand-based models for assessing health personnel supply requirements to the field of physical therapy. Definitions and examples of these models are offered. Problems presented in the field of physical therapy in accurately defining need and demand are presented. Specific examples of current data collection at a variety of levels (professional association, private sector, state, and federal) are given.

Health Planning↗

PubMed2000

Cardiorespiratory fitness and coronary heart disease risk factors: the LDS Hospital Fitness Institute cohort.

BACKGROUND: Cardiorespiratory fitness is favorably associated with most modifiable coronary heart disease (CHD) risk factors. Findings are limited, however, by few data for women, persons with existing CHD, and low-risk populations. In the present study, we described cross-sectional associations between cardiorespiratory fitness and CHD risk factors in a large cohort of middle-aged men and women, of whom the majority were LDS Church members (Mormons), with and without existing CHD. METHODS AND RESULTS: Comprehensive health examinations were performed on 3232 men (age 45.9+/-10.8 years) and 1128 women (age 43.8+/-12.8 years) between 1975 and 1997. Maximal treadmill exercise testing was used to categorize those with (12% of the men and 10% of the women) and those without CHD into age- and sex-specific cardiorespiratory fitness quintiles. After adjustments for age, body fat, smoking status, and family history of CHD, favorable associations were observed between fitness and most CHD risk factors among men and women, regardless of CHD status. CONCLUSIONS: These data indicate that enhanced levels of cardiorespiratory fitness may confer resistance to elevations in CHD risk factors even in a low-risk sample of middle-aged men and women. Furthermore, these findings reinforce current public health recommendations that advocate increased national levels of physical activity and cardiorespiratory fitness for primary and secondary CHD prevention.

Cohort Studies↗

PubMed2000

The RsaI polymorphism in the alpha-fibrinogen gene and response of plasma fibrinogen to physical training--a controlled randomised clinical trial in men.

We have previously reported cross-sectional data on an interaction effect between physical activity and alpha-fibrinogen RsaI polymorphism on fibrinogen in postmenopausal women. In the present controlled randomised study, we investigated the role of the RsaI polymorphism in determining the response of fibrinogen to long-term regular exercise. Middle-aged men (n = 140), randomly selected from the population registry, were randomised into an exercise or a reference group for a 3-year low intensity exercise intervention. Complete data were available in 125 men. The RsaI restriction enzyme detects threonine (Thr) to alanine change in the fibrinogen alpha codon 312. Anaerobic ventilatory threshold increased by 4%, but decreased by 2% in the exercise and reference groups, respectively. Mean fibrinogen did not decrease in either study group. However, in the exercise group, individual changes in anaerobic threshold explained 48% of the variance in fibrinogen changes in the Thr homozygotes. Our data offer a new aspect of beneficial effects of regular physical exercise on risk factors for coronary heart disease.

Amino Acid Substitution↗

PubMed1993

Value of the history and physical in identifying patients at increased risk for coronary artery disease.

OBJECTIVE: To determine whether information from the physician's initial evaluation of patients with suspected coronary artery disease predicts coronary anatomy at catheterization and 3-year survival. DESIGN: Prospective validation of regression model estimates in an outpatient cohort. SETTING: University medical center. PATIENTS: A total of 1030 consecutive outpatients referred for noninvasive testing for suspected coronary artery disease; 168 of these patients subsequently underwent catheterization within 90 days. MEASUREMENTS: Information from the initial history, physical examination, electrocardiogram, and chest radiograph was used to predict coronary anatomy (the likelihood of any significant coronary disease, severe disease [left main or three-vessel], and significant left main disease) among 168 catheterized patients and to estimate 3-year survival among all patients. These estimates were compared with those based on treadmill testing. Cardiovascular testing charges were calculated for all patients. RESULTS: Predicted coronary anatomy and survival closely corresponded to actual findings. Compared with the treadmill exercise test, initial evaluation was slightly better able to distinguish patients with or without any coronary disease and was similar in the ability to identify patients at increased risk for dying or with anatomically severe disease. Based on arbitrary definitions, 37% to 66% of patients were at low risk and responsible for 31% to 56% of the charges for cardiovascular testing. CONCLUSIONS: The physician's initial evaluation, despite the subjective nature of much of the information gathered, can be used to identify patients likely to benefit from further testing. The development of strategies for cost-conscious quality care must begin with the history, physical examination, and simple laboratory testing.

Aged↗