*2.7. Other Variables Measured*

Ergonomic Practices were measured using three items from Amick et al. [47]: "Ergonomic strategies are used to improve the design of work", "Ergonomic factors are considered in task pre-planning and in purchasing new tools or equipment", and "Ergonomic factors are considered in safety and health inspections". These were rated on a 5-point scale ranging from 1 = strongly agree to 5 = strongly disagree. Ergonomic practice items were coded for the analysis so that higher scores of ergonomic practices represented better ergonomic practices.

Work limitations were measured using the eight question short-form Work Limitations Questionnaire, which contained domains on time, physical, mental and interpersonal demands [48]. Responses on a 5-point Likert scale were coded for the analysis so that higher values on the work limitations scale represented more or higher work limitations.

Physically demanding job demands were measured by two ordinal variables stemming from the following questions: "Please indicate how physically demanding your job is over the last 7 days", on a scale ranging from 1 = "not at all physically demanding" to 5 = "extremely physically demanding".

Sociodemographic variables included age (years), sex (male/female), race (white, black/African American, Latino/Hispanic, other), education level, job title (apprentice, journeyman, foreman and supervisor), and construction trade (carpenters, electricians, drywallers, ironworkers, laborers, painters, pipefitters, and plumbers). Race and ethnicity were later combined into the following two categories: "white" and "not white" for the analysis. Job title was later categorized into two categories for the analysis: "apprentice/journeyman", and "foreman/supervisor". Trade was categorized into the following four categories based on workers' job demands: (1) mechanical; (2) finishing; (3) ironwork; and, (4) labor. These categorizations have been used previously [36].
