Perceived physical exertion in senior workers performing heavy manual tasks

With an aging workforce and longer working lives, staying in physically demanding occupations is increasingly challenging, and the factors influencing perceived exertion are still poorly understood. Also, self-rated exertion may not correlate strongly with physiological measurements of physical strain at work, such as heart rate. Our study aimed to describe the physical strain experienced by senior workers in manual occupations using Borg's Rating of Perceived Exertion (RPE) scale and to explore associations between personal variables such as heart rate during work, age, physical fitness, and RPE ratings. We recruited workers aged 50 yr or older in manual occupations and collected data using questionnaires, physical examinations, field heart rate monitoring, and RPE ratings during work. Field heart rate monitoring was conducted using a chest band with a pulse sensor that transmitted data to a mobile application, and the first 6 h of recordings were used in subsequent analyses. Subjects were asked to simultaneously complete a diary at the end of each shift, rating the overall physical exertion for that day using the RPE scale, ranging from 6 (rest) to 20 (maximal physical exertion). Correlation between variables was determined using Spearman's rank correlation coefficient (r). A linear mixed model was used to investigate associations between personal variables and RPE ratings. The sample consisted of 126 subjects, aged 50 to 67 yr, of whom 76 (60.3%) were females. The participants were employed as construction workers, kitchen workers, cleaners, or assistant nurses. They rated perceived physical exertion on the RPE scale once daily in one to three workdays, resulting in a total of 250 workdays. The mean (SD) RPE rating was 12.1 (2.1). When stratified by sex, the mean (SD) RPE rating was 12.1 (2.2) among females and 12.0 (1.8) among males (P = 0.669). When stratified by occupational group, the mean (SD) was 11.9 (1.9) for construction workers, 12.1 (2.0) for kitchen workers, 12.4 (1.6) for cleaners, and 11.8 (2.8) for assistant nurses (P = 0.139 to 0.815). In total, 298 heart rate (HR) recordings were obtained during work with a mean (SD) HR of 89.4 (11.4) beats/min (range 54 to 125). There was a significant bivariate correlation between the RPE ratings and mean HR for the entire study population (r = 0.14; P = 0.025) as well as in the group of construction workers (r = 0.23; P = 0.042), but not for any other occupational groups (r = 0.04 to 0.25; P = 0.096 to 0.752). In the linear mixed model, using the RPE ratings as the dependent variable, the statistically significant (P < 0.05) estimated coefficients (SE) were as follows: mean heart rate (beats/min), 0.03 (0.01); very poor sleep quality, 3.38 (0.93); and high psychological stress, 2.62 (0.71). Age, body mass index, theoretical maximum oxygen consumption, and chronic pain ratings were not significantly associated with the RPE ratings. We conclude that senior workers in manual occupations reported that their work was somewhat hard in terms of physical exertion. Our study also indicates associations between mean heart rate, sleep quality, psychological stress, and RPE ratings.