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.

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.

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.

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.

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.

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.

Modelos de ecuaciones estructurales aplicados al análisis de fatiga / Structural Equation Models Applied to Human Fatigue Analysis / Modelos de equações estruturais aplicados à análise de fadiga

Objetivos: este artículo presenta una descripción de los principales elementos y componentes de los modelos de ecuaciones estructurales, así como de los valores estadísticos de referencia para evaluar estos modelos. Además, se muestran los principales modelos desarrollados para el análisis de fatiga humana. Materiales y métodos: tras una revisión de literatura, se identificaron siete esquemas que examinan causas, efectos y relaciones entre variables, dimensiones y constructos relacionados con la fatiga en diferentes ambientes y situaciones laborales o de laboratorio. Conclusiones: los modelos de ecuaciones estructurales son una herramienta útil que contribuye a la generación de conocimiento en temas relacionados con la fatiga humana.

Objectives: this article provides a brief description of the main elements and components of Structural Equation Models (SEM) and statistical reference values to evaluate those models. Additionally, main models developed for human fatigue analysis are presented. Materials and methods: through a literature review, 7 models that analyze causes, effects, and relationships between variables, dimensions, and constructs related to fatigue in different work environments were identified. Conclusion: structural equation modeling is a useful tool that contributes to the generation of knowledge on topics related to human fatigue.

Este artigo apresenta uma descrição dos principais elementos e componentes dos modelos de equações estruturais, assim como dos valores estatísticos de referência para avaliar estes modelos. Adicionalmente, se apresentam os principais modelos desenvolvidos para a análise de fadiga humana. Através de uma revisão de literatura, foram identificados 7 modelos que analisam causas, efeitos e relações entre variáveis, dimensões e construtos relacionados com a fadiga em diferentes ambientes e situações laborais ou de laboratório. Através dos modelos identificados, conclui-se que os modelos de equações estruturais são uma ferramenta útil que contribui à geração de conhecimento em temas relacionados com a fadiga humana.

Construction of a survey to assess workload and fatigue among AMT operators in Mexico.

UNLABELLED: Operators of machinery classified as Advanced Manufacturing Technology (AMT) are exposed to high levels of workload and fatigue. However, only few studies have been conducted on this topic in Hispanic-American countries workers. Several instruments be used to assess workload and fatigue; however, only few of them have been adapted to Spanish language. This paper reports on the development and validity testing of a survey instrument in Spanish, aiming to subjectively assess workload and fatigue among AMT operators in Mexico. METHOD: After an exhaustive literature review in search of already available measurement instruments, they were adapted for content and later translated into Spanish; a pilot test was conducted to evaluate validity and reliability; afterwards appropriate modifications were made to the testing instruments. Final version of the instrument was applied to a group of 121 operators of CNC lathes. Reliability was analyzed using KMO and Cronbach alpha indices. RESULTS: For the assessment of workload, both NASA-TLX and ISTAS 21 methods were incorporated to the survey instrument. As for fatigue assessment tools, these were SOFI-S, FAS and OFER questionnaires. RESULTS show KMO value and Cronbach alpha above 0.6.Conclusions. The survey instrument as designed, allows the collection of reliable and valid data regarding workload and fatigue among AMT operators in Mexico.