Study of musculoskeletal disorders risk factors and discomfort in sculptors in the north of Mexico.

BACKGROUND: The sculpting craft must adopt awkward postures that lead to musculoskeletal disorders (MSDs). OBJECTIVE: This study investigated the prevalence of musculoskeletal discomfort (MD) and its associations with postural risk factors, demographics, and work characteristics among sculptors. They were determined the differences between MDs during the weeks of the study. METHODS: A longitudinal study was conducted; MD was investigated using the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ). Posture was assessed using the Rapid Upper Limb Assessment method (RULA). Multivariate logistic regression (MLR) models analyzed associations with different factors. ANOVA was used to test for differences in MD prevalence. RESULTS: The analysis included 585 responses by body region. The prevalence of MD was high in the lower and upper limbs among sculptors (67.6%), with the lower back, upper arm, neck, and knees being the four most affected regions. Gender (female) (OR = 2.15), marital status (married) (OR = 1.80), health risk (obesity), the dual of a secondary job (OR = 1.94), job stress (OR = 2.10), duration of work (OR = 2.01), and difficulty keeping up with work (OR = 2.00) were significant predictors contributing to the occurrence of MD in different body regions. Only shoulder MD prevalence showed significant differences between study weeks. CONCLUSIONS: Sculptors suffer from MD. Demographic and work characteristic factors influence MD prevalence. Postural training, improved adaptation of work organization, and intervention guidance on ergonomic risks may reduce the prevalence of MD and the risk of MSDs in this population.

Cognitive Analyses for Interface Design Using Dual N-Back Tasks for Mental Workload (MWL) Evaluation.

In the manufacturing environments of today, human-machine systems are constituted with complex and advanced technology, which demands workers' considerable mental workload. This work aims to design and evaluate a Graphical User Interface developed to induce mental workload based on Dual N-Back tasks for further analysis of human performance. This study's contribution lies in developing proper cognitive analyses of the graphical user interface, identifying human error when the Dual N-Back tasks are presented in an interface, and seeking better user-system interaction. Hierarchical task analysis and the Task Analysis Method for Error Identification were used for the cognitive analysis. Ten subjects participated voluntarily in the study, answering the NASA-TLX questionnaire at the end of the task. The NASA-TLX results determined the subjective participants' mental workload proving that the subjects were induced to different levels of mental workload (Low, Medium, and High) based on the ANOVA statistical results using the mean scores obtained and cognitive analysis identified redesign opportunities for graphical user interface improvement.

Comparing workload and performance during demanding push force and mental tasks.

BACKGROUND: The effects of performing occupational tasks that demand physical and mental efforts in combined and simultaneous approaches are unknown, especially when pushing force is analyzed as a physical effort and solving arithmetic problems as a mental effort. OBJECTIVE: In this study, physical and mental demands were simulated in a lab environment to assess the workload. METHODS: Using a push force dynamometer, the maximum push force strength of each participant was recorded, and the physical demand was simulated exerting the push force in low, medium, and high levels. Mental demands were simulated solving arithmetic tasks in low, medium, and high levels. Two experimental conditions were defined: (1) task with combined physical and mental workload (performing physical demands first and mental demands after) and (2) task in a simultaneous way (performing both demands at the same time. NASA-TLX Traditional and RAW were applied to assess the workload. RESULTS: The time to complete the tasks was significantly longer in the combined than the simultaneous approach, and performance was significantly higher in the combined than the simultaneous tasks. CONCLUSION: The combined approach obtained better results than simultaneous and Traditional NASA-TLX presented a significantly higher level of global workload index than RAW.

Impact of experience on the sensitivity, acceptability, and intrusive of two subjective mental workload techniques: The NASA TLX and workload profile.

BACKGROUND: Today's work environments have high cognitive demands, and mental workload is one of the main causes of work stress, human errors, and accidents. While several mental workload studies have compared the mental workload perceived by groups of experienced participants to that perceived by novice groups, no comparisons have been made between the same individuals performing the same tasks at different times. OBJECTIVE: This work aims to compare NASA Task Load Index (NASA-TLX) to Workload Profile (WP) in terms of their sensitivity. The comparison considers the impact of experience and task differentiation in the same individual once a degree of experience has been developed in the execution of the same tasks. It also considers the acceptability and intrusivity of the techniques. METHODS: The sample consisted of 30 participants who performed four tasks in two sessions. The first session was performed when participants had no experience; the second session was performed after a time of practice. Mental workload was assessed after each session. Statistical methods were used to compare the results. RESULTS: The NASA-TLX proved to be more sensitive to experience, while the WP showed greater sensitivity to task differentiation. In addition, while both techniques featured a similar degree of intrusivity, the NASA-TLX received greater acceptability. CONCLUSION: The acceptability of WP is low due to the high complexity of its dimensions and clarifying explanations of these may be necessary to increase acceptability. Future research proposals should be expanded to consider mental workload when designing work environments in current manufacturing environments.

Influence of an armrest support on handgrip strength in different arm and shoulder flexion angles in overhead postures.

A study was undertaken in which the handgrip strength in three arm positions above the shoulder was measured to compare handgrip strength when arm support is used and when it is not used. Grip forces were generated in pairs of flexion angles, corresponding to shoulder and elbow at 90°-90°, 135°-45° and 160°-20°. Thirty-two participants completed the present study; 23 men and nine women with a median age of 23.1 (SD ±3.6) years. A manual handgrip dynamometer (0-90 kg) and an adjustable angle arm support (AAAS) were used during the data collection. Two-way analysis of variance (ANOVA) for repeated measurements indicates a significant effect of the AAAS factor on the handgrip strength, as well as on the AAAS × angle interaction. However, there is no significant effect of the angle factor on the AAAS × angle interaction.

Impact of job strain and being overweight on middle and senior managers from the manufacturing sector in the Mexican industry.

BACKGROUND: This research work establishes the relationship between job strain and being overweight among Mexican managers. Recently in Mexico, there has been a sharp increase in work-related diseases and mental health disorders. Furthermore, evidence shows that Mexicans rank top among employees who suffer from stress, yet research on the impact of job strain on the phenomena of obesity and being overweight among such vulnerable job positions in the industrial field is scarce. METHODS: The sample included 170 overweight middle and senior managers from six companies in the Mexican Manufacturing Industry. Cedillo's Spanish version of the Job Content Questionnaire by Karasek was used, and the Body Mass Index (BMI) was used to characterize an overweight condition. Structural Equations Modelling studied the relationships among variables. RESULTS: Even though, the model shows a power of explanation of 6%(R2 = 0.06), the variable showing the greatest direct effect on the overweight variable is social support, with 21%(p < 0.01, ß= -0.21). Regarding the total effects, only two of the four variables studied contributed directly to the overweight variation: the social support variable and the job demand variable. CONCLUSIONS: The results of the model hold a relatively low explanatory power; however, they do show a relationship between the studied variables. Also, the importance of the supervisor and co-workers' support should be considered when developing organizational strategies for the prevention of work stress and an overweight condition.

The Relationship Between the Burnout Syndrome Dimensions and Body Mass Index as a Moderator Variable on Obese Managers in the Mexican Maquiladora Industry.

Burnout syndrome (BS) and obesity are two growing conditions that affect employees' health and company productivity. Recently, several studies have pointed to a possible relationship between both phenomena. However, such a relationship has not been clearly defined. This research analyzes the relationship between BS dimensions and body mass index (BMI), the latter being treated as a moderator variable among obese senior and middle managers in the Mexican maquiladora industry through a structural equation model. A total of 361 senior and middle managers (124 of them classified as obese under the World Health Organization's criteria) completed both the Maslach Burnout Inventory-General Survey [with emotional exhaustion (EE), cynicism, and professional efficacy (PE) as subscale dimensions] and a sociodemographic questionnaire (which included BMI). The results showed a statistically significant relationship between EE and PE (P < 0.001; ß = -0.320), with BMI acting as a moderator variable. The results showed that when BMI increases as a moderator variable, the strength of the relationship between EE and PE also changes. For example, although PE had a negative value of 0.14 before the moderator effect, the value increased up to 0.32 when the BMI was factored into the relationship. Therefore, maquiladora industries are being advised to increase their investments on the identification and prevention of employees' EE and obesity. Such interventions would promote a better quality of life and could prevent economic losses resulting from poor employee performance.

Effects of Job Content and Physical Activity on Body Mass Index among Obese Managers of the Mexican Manufacturing Industry.

Mental health disorders resulting from work stressors are increasing in the Mexican manufacturing industry and worldwide. Managerial positions in these contexts are highly stressful, and although physical activity may reduce the negative effects of work stress, the relationships between these two aspects regarding their effects on the body mass index (BMI) of obese managers are scarcely studied. This article aims to study such relationships by using the Job Content Questionnaire (JCQ) dimensions with the Baecke's physical activity questionnaire dimensions and analyzing their effects on the BMI. A sample of 255 managers from the Mexican industry, with a (BMI > 30) participated by answering the surveys and providing their weight, their height, and certain sociodemographic information. The research hypotheses were tested using WarpPLS® 6.0 for structural equation modeling. The results for three models featuring acceptable reliability to estimate the direct, indirect, and total effects are presented. The first model showed a medium explanatory power, the variable of job decision-making authority having the greatest direct effect on BMI. The second model showed a medium explanatory power, and the variable of physical activity during leisure-time observed the unique direct effect on BMI. Finally, although the integrating model showed a small explanatory power, both work stress and the physical activity exerted observed direct effects on BMI reduction.

Análisis cognitivos de carga mental e identificación del error humano para mejorar la experiencia de usuario / Cognitive analyses of mental workload and human error identification for the improvement of user experience

Resumen Las personas, en ocasiones, pueden sentirse abrumadas al tratar de interactuar con la tecnología moderna. Ciertos productos de uso cotidiano cuentan con diseños deficientes, por lo que pueden provocar una experiencia insatisfactoria y frustración, produciéndose con ellas una carga mental en el usuario que pueda inducir al error. El uso de técnicas para la identificación del error humano y de la evaluación de carga mental en el diseño y evaluación de productos, puede proporcionar información relevante y útil, para mejorar la experiencia del usuario. El objetivo de este trabajo fue proponer una metodología para integrar la evaluación de carga mental y el análisis del error humano en el diseño de productos. Se evaluó la carga mental mediante la técnica perfil de carga de trabajo, Workload Profile (WP), y se utilizó una metodología de identificación del error humano, Task Analysis For Error Identification (TAFEI), en la configuración de audífonos inalámbricos. Diez usuarios participaron voluntariamente en el estudio; sus experiencias en el uso de los audífonos fueron videograbadas. Se utilizaron formularios para evaluar carga mental, y se identificaron errores humanos durante la etapa de configuración de los audífonos con el teléfono móvil. El método utilizado en este trabajo ofrece una mayor sensibilidad en la evaluación de la carga mental y permite determinar los recursos de atención que más se utilizan en la realización de la tarea. Se detectaron dos oportunidades de rediseño, una relacionada con la señal lumínica, y la otra para la identificación de las puntas para cada oído. A partir de los resultados de la aplicación de la metodología propuesta en este estudio, los diseñadores pueden mejorar la interacción entre las personas y los productos.

Abstract People can sometimes feel overwhelmed when trying to interact with modern technology. Some everyday products have deficient designs which can result in an unsatisfactory experience and even frustration. Additionally, they may produce a mental workload that can induce the user to make mistakes during their usage. The use of techniques for human error identification and mental load assessment in products evaluation and design can provide relevant and useful information to improve the user's experience. The objective of this work was to propose a methodology for integrating mental workload assessment and human error analysis into product design processes. In this work, mental workload was evaluated during the configuration of wireless earphones using the Workload Profile (WP) technique, and the Task Analysis for Error Identification (TAFEI). Ten users voluntarily participated in the study; their experiences during the use of mobile phone earphones were video recorded. Rating sheets were used to assess mental workload and human errors were identified during the earphones' setup stage with the mobile phone. The method employed for this research offers higher sensitivity in the assessment of mental workload. It also enables the identification of attention resources that were more frequently used during task completion. Two opportunities for redesign were identified. The first one is related to the light signal detection and the second one to the correct identification of ear tips. Conclusions and recommendations are given for designers to improve the interaction between people and products.

Design and validation of a questionnaire in Spanish language for software usability evaluation.

BACKGROUND: Usability is an essential characteristic of software development, which needs to be evaluated mainly through questionnaires. However, the questionnaires available in Spanish are limited and not available for most software's developers and users. OBJECTIVES: This work aimed to design and validate a new questionnaire to evaluate software usability, considering the characteristics of efficiency, effectiveness, and satisfaction as defined by the International Standards Organization. METHODS: The Software Usability Assessment Questionnaire or SUAQ in Spanish language was designed and validated using Kendall's coefficient, Cronbach's Alpha, Factorial Analysis and Scree test. RESULTS: The questionnaire's validation was carried out by five experts through an evaluation of the clarity, coherence, and relevance of the proposed items. Once the questionnaire was administered to 95 participants, an overall reliability value of Cronbach's alpha of 0.839 was obtained. The factorial analysis is viable since a value of 0.757 was found in the Kaiser-Meyer-Olkin (KMO) test, and a significant value was obtained in Bartlett's sphericity test. CONCLUSIONS: The proposed questionnaire proved to be valid and reliable, and therefore, suitable to evaluate software usability in the Spanish language.

Burnout Syndrome in Middle and Senior Management in the Industrial Manufacturing Sector of Mexico.

Due to globalization and the accelerated growth of technology, ever more employees of companies are affected by burnout syndrome, the psychological nature of which requires a prolonged response to chronic interpersonal stressors in work environments. The present research aims to validate the operability of the Maslach Burnout Inventory-General Survey (MBI-GS) using a sample of 378 professionals belonging to middle and senior management working in companies within the IMMEX sector (comprising the industrial-manufacturing, maquiladora and export services) located in the state of Baja California, Mexico. Firstly, an exploratory factor analysis using the principal components method and Varimax rotation was performed and the results revealed the existence of three factors representing more than 67 percent of the total variance. Secondly, a confirmatory factorial analysis was carried out performing appropriate results for the indices Chi-square goodness-of-fit model, Root Mean Square Error of Approximation (RMSEA), Normed Fit Index (NFI), Comparative Fit Index (CFI), Relative Fit Index (RFI), Parsimony Ratio (PRATIO) and Parsimony Normed Fit Index (PNFI), which are highly recommended by literature in these types of studies. Additionally, construct validity was satisfactorily verified. The factorial solution coincided with the Maslach Burnout Inventory original proposal so that this instrument can be considered a valid and reliable option to analyze the burnout levels in people pertaining to middle and senior management in these types of industries.

Physiological and Subjective Responses Associated to Physical and Mental Load in a Simulated Task / Respuestas fisiológicas y subjetivas asociadas a la carga física y mental en una tarea simulada / Respostas fisiológicas e subjetivas associadas à carga física e mental em uma tarefa simulada

Abstract Objective: To develop a quasi-experimental study to know the changes in physiological responses and perceived efforts of a group of fifteen healthy students that performed a simulated task related with the operation of a CNC lathe in a lab environment. Materials and Methods: The participants were asked to randomly complete a total of eight sessions including single and combined test of physical and mental load. Low/High Physical Load and Low/ High Mental Load were established as independent variables. Heart rate, physical performance, mental performance, and effort perception were established as dependent variables. Conclusions: High load levels have a significant effect on the heart rate increasing, but not in the perception of effort. High levels of mental load have a significant effect on physical and mental performance.

Resumen Objetivo: Desarrollar un estudio quasi-experimental para conocer los cambios en las respuestas fisiológicas y esfuerzos percibidos en un grupo de quince estudiantes sanos que realizaron una tarea simulada relacionada con la operación de un torno CNC en ambiente de laboratorio. Materiales y métodos: Los participantes completaron un total de ocho sesiones que incluyeron pruebas individuales y combinadas de esfuerzo físico y mental. La Carga Mental Baja/Alta y Carga Física Baja/Alta fueron establecidas como variables independientes. Frecuencia cardiaca, desempeño físico, desempeño mental y la percepción de esfuerzo fueron establecidas como variables dependientes. Conclusiones: Los niveles altos de carga física tienen un efecto significativo en el incremento de la frecuencia cardiaca, pero no en la percepción de esfuerzo. Los niveles altos de carga mental tienen un efecto significativo en el desempeño físico y mental.

Resumo Objetivo: Desenvolver um estudo quase-experimental para conhecer as mudanças nas respostas fisiológicas e esforços percebidos em um grupo de 15 estudantes saudáveis que realizaram uma tarefa simulada relacionada com a operação de um torno CNC em ambientes de laboratório. Materiais e métodos: Os participantes completaram um total de 8 sessões que incluíram provas individuais e combinadas de esforço físico e mental. A Carga Mental Baixa/Alta e a Carga Física Baixa/Alta foram estabelecidas como variáveis independentes. Frequência cardíaca, desempenho físico, desempenho mental e a percepção de esforço foram estabelecidas como variáveis dependentes. Conclusões: Os níveis altos de carga física têm um efeito significativo no incremento da frequência cardíaca, mas não na percepção de esforço. Os níveis altos de carga mental têm um efeito significativo no desempenho físico e mental.

Relationship between Burnout and Body Mass Index in Senior and Middle Managers from the Mexican Manufacturing Industry.

This research relates Burnout Syndrome (BS) with the Body Mass Index (BMI) among middle and senior managers of the Mexican manufacturing industry. Even though BS incidence is high in the Mexican industrial population, few systematic studies have explored BS and its relationship with other health problems, such as obesity. The goal of this research is to determine the relationship between BS and the BMI in employees with normal weight, overweight, and obesity. We present three structural equation models to relate BS and the BMI. The BMI ranges were determined according to the parameters (normal weight, overweight, and obesity) proposed by the World Health Organization (WHO). The sample includes 361 employees that voluntarily answered a 31-item questionnaire. We measure the levels of BS using the Maslach Burnout Inventory-General Survey (MBI-GS) and analyze anthropometric and sociodemographic data from the participants. Then, we determine the relationships between the variables through structural equation models and estimate the direct, indirect, and total effects in the three models, which show acceptable reliability. As main findings, the normal weight model has a larger explanatory power than the overweight and obesity models. The same research hypotheses were tested and the effects of BS on the BMI differ across the three models. Such results are presented by taking into account that obesity and overweight require additional factors, such as genetic factors and personal eating habits, to be better explained.

Analysis of burnout syndrome, musculoskeletal complaints, and job content in middle and senior managers: Case study of manufacturing industries in Ciudad Juárez, Mexico.

BACKGROUND: In developing countries such as Mexico, the effects of burnout syndrome (BS) are observed in manufacturing industries. However, the relationships among BS, Job Content (JC), and Musculoskeletal Complaints (MC) are scarcely studied within the manufacturing sector, even though senior and middle managers are exposed to highly demanding and mentally exhausting situations. OBJECTIVES: The objective of this paper is to determine the relationships among the three BS dimensions, MC, and JC among middle and senior managers of the manufacturing industry in Ciudad Juárez, Mexico. METHODS: The Maslach Burnout Inventory-General Survey (MBI-GS), the Job Content Questionnaire (JCQ), and the Body Map assessment were administered as data collection instruments. The sample included 361 participants from six industries located in Ciudad Juárez, Mexico. Also, we proposed structural equations models (SEM) to establish the relationships among variables. RESULTS: The questionnaires and the model showed acceptable reliability and quality indices. Emotional exhaustion was the most relevant latent variable, having significant effects on MC and on professional efficacy, and significantly contributing to increasing levels of cynicism. On the other hand, the variable social support showed a negative direct impact on Job Demands and Emotional Exhaustion. CONCLUSIONS: Actions to reduce emotional exhaustion at work include providing a positive and suitable work environment through social support. These strategies help prevent MC and improve professional efficacy, life quality at work, and productivity.

Structural Model for the Effects of Environmental Elements on the Psychological Characteristics and Performance of the Employees of Manufacturing Systems.

This paper analyzes the effects of environmental elements on the psychological characteristics and performance of employees in manufacturing systems using structural equation modeling. Increasing the comprehension of these effects may help optimize manufacturing systems regarding their employees' psychological characteristics and performance from a macroergonomic perspective. As the method, a new macroergonomic compatibility questionnaire (MCQ) was developed and statistically validated, and 158 respondents at four manufacture companies were considered. Noise, lighting and temperature, humidity and air quality (THAQ) were used as independent variables and psychological characteristics and employees' performance as dependent variables. To propose and test the hypothetical causal model of significant relationships among the variables, a data analysis was deployed. Results found that the macroergonomic compatibility of environmental elements presents significant direct effects on employees' psychological characteristics and either direct or indirect effects on the employees' performance. THAQ had the highest direct and total effects on psychological characteristics. Regarding the direct and total effects on employees' performance, the psychological characteristics presented the highest effects, followed by THAQ conditions. These results may help measure and optimize manufacturing systems' performance by enhancing their macroergonomic compatibility and quality of life at work of the employees.

Ergonomic assessment for the task of repairing computers in a manufacturing company: A case study.

BACKGROUND: Manufacturing industry workers who repair computers may be exposed to ergonomic risk factors. OBJECTIVES: This project analyzes the tasks involved in the computer repair process to (1) find the risk level for musculoskeletal disorders (MSDs) and (2) propose ergonomic interventions to address any ergonomic issues. METHODS: Work procedures and main body postures were video recorded and analyzed using task analysis, the Rapid Entire Body Assessment (REBA) postural method, and biomechanical analysis. RESULTS: High risk for MSDs was found on every subtask using REBA. Although biomechanical analysis found an acceptable mass center displacement during tasks, a hazardous level of compression on the lower back during computer's transportation was detected. CONCLUSIONS: This assessment found ergonomic risks mainly in the trunk, arm/forearm, and legs; the neck and hand/wrist were also compromised. Opportunities for ergonomic analyses and interventions in the design and execution of computer repair tasks are discussed.

Human factors identification and classification related to accidents'causality on hand injuries in the manufacturing industry.

The causes of occupational accidents from the perspective of human factors have been a subject which has received little attention into the field of scientific research. The aim of this research was to identify and classify the human factors that influence human errors and failures that cause accidents and injuries specifically on hands. Available studies related to the topic have been developed mainly for aerospace applications and are found insufficient to explain accidents causalities in the manufacturing industry. This research was developed in the assembly industry of automotive harnesses and was conducted following a mixed Cognitive Anthropological approach. This study was developed in two phases. During the first qualitative phase, participants freely listed their knowledge to identify elements of the cultural domain, then and in the second phase they performed the successive pile sort technique for the collection data to classify elements in the cultural domain. Statistical models like Cluster Analysis and Multidimensional Scaling were applied for results' validation purposes. As results, 70 different human factors were identified and in the second phase they were classified into 4 main categories which were: human error, unsafe conditions, individual factors, and organizational factors. Statistical methods validated these results.