Factors associated with high physical exertion during manual lifting: Cross-sectional study among 200 blue-collar workers

BACKGROUND: High physical exertion during work is a risk factor for back pain and long-term sickness absence. OBJECTIVE: To investigate which factors are associated with physical exertion during manual lifting. METHODS: From 14 workplaces across Denmark, 200 blue-collar workers reported perceived physical exertion (Borg-CR10) during manual lifting from floor to table height of 5, 10, 20 and 30 kg at the beginning and end of the working day. The workers also responded to a questionnaire and went through testing of isometric back muscle strength. Associations were modelled using logistic regression analysis controlled for various confounders. The outcome was dichotomized into low (0-4) and high (5-10) physical exertion. RESULTS: Gender (OR 8.57 [95% CI 4.46-16.46] for women), load (OR 4.22 [95% CI 3.58-4.97] for each 5-kg increase), back muscle strength (OR 0.43 [95% CI 0.23-0.83] for high), and back pain intensity (OR 2.80 [95% CI 1.43-5.48] for high) were associated with high perceived physical exertion. Age, smoking, Body Mass Index (BMI), and time of the day were not associated with physical exertion. CONCLUSIONS: Gender, load, back muscle strength and back pain influence physical exertion during manual lifting in blue-collar workers. These factors should be considered when planning work with manual lifting for individual workers.