Perceived exertion of physical effort for various manual handling tasks.

Ten trained male students between 18 and 28 years of age participated in a study, designed to determine the relationship between perceived exertion and physiological costs of exertion during various manual lifting and lowering tasks. Perceived exertion was defined as one's subjective rating of the intensity of work being performed. Five subjects performed lifting tasks and another five performed lowering tasks. Weight of load lifted or lowered (6.8, 13.6, 20.5 kg), frequency of lift or lower (3, 6, 9 times/min), height of lift or lower (floor to 76 cm, 76 to 127 cm, floor to 127 cm), box width (38, 66 cm), box length (38, 66 cm) and angle of twist of the body (0 degree, 90 degrees) were the independent variables studied. Heart rate, oxygen consumption, and ratings of perceived exertion (RPE) were the response measures. RPE was found almost linearly related to heart rate and oxygen consumption when lifting or lowering loads. For lifting tasks, the coefficient of correlation between RPE and heart rate was 0.673. In the case of lowering tasks, this coefficient was 0.604. When oxygen consumption was considered, the corresponding coefficients for lifting and lowering were 0.734 and 0.619, respectively. The correlation of RPE with the physiological response variables indicates that the severity of manual materials handling tasks in industry can be evaluated quickly and inexpensively by using perceived exertion ratings (RPE).