Physiological and perceptual responses in male Chinese workers performing combined manual materials handling tasks

A study on combined manual materials handling (MMH) tasks, under two different frequencies and four lifting and lowering height combinations, was conducted in Beijing, China. Eight male construction workers performed a box handling task repetitively for an hour either at once or twice per minute. On each day, the task consisted of: lifting a box of ceramic tile weighting 23 kg from a specified height, carrying it for 8.5 m, lowering the box to a specified height, and then walking 8.5 m back. The specific heights included: lifting the box from floor and lowering it onto the floor (F–F); lifting from the floor and lowering to the knuckle height (F–K); lifting from knuckle height and lowering onto the floor (K–F); and lifting from knuckle height and lowering to the knuckle height (K–K). Oxygen uptake, heart rate, and ratings of perceived exertion (RPE) for whole body were measured during the task. Additionally, actual energy expenditure of the box handling for an hour was calculated from the oxygen uptake measured, whereas the predicted energy expenditure was estimated using the valid regression equations available in the literature. Statistical analysis demonstrated that both task frequency and lifting and lowering heights influence oxygen uptake, heart rate, and the RPE (p < 0.05). The RPE during the task frequency of twice per minute was higher than that of once per minute. The RPE for the F–F and F–K conditions were both higher than that of the K–K condition. The difference between the actual and predicted energy expenditures was not statistically significant. This implies that the predictive equations used in this study are acceptable in estimating the physiological cost of Chinese construction workers performing similar MMH tasks as in this study.Relevance to industryCombined MMH tasks are very common on construction sites. This study investigated the physiological and subjective responses in Chinese construction workers performing combined MMH tasks. A predictive model in the literature was also examined to determine whether it could be used to describe the energy expenditure of these workers.