Physiological Workload during Backpack Carrying Tasks of the Soft Drink Beverage Delivery Jobs

Abstract

The deliveries of the soft drink beverages in Korea are made for a broad line of soft drink products by using a hand truck and a backpack mode of carrying. The workers usually deliver the beverages by backpack mode of carriage, because they feel safer with the method on a stairway. In this study, we investigated the effects of weight of load and work conditions upon the physiological workload of backpack carrying tasks. A laboratory experiment was conducted to measure the heart rate and oxygen uptake during backpack carrying tasks, and to propose ergonomic guidelines for such tasks based on the results of the experiment. Eight healthy male field workers participated in the experiment to perform the backpack carrying of 40 kg and 60 kg with the work conditions of (1) the leveled ground, (2) upstairs and (3) downstairs. The results showed that the stairways caused the increased physiological cost, and that a carrying load of 60 kg required significantly higher physiological cost as compared to carrying 40 kg. The average heart rate increased up to 150 bpm when carrying 40 kg on the stairs, indicating a need for ergonomic intervention. Although backpack carrying has some advantages in the biomechanical aspect, it should be advised to carry a load of less than 40 kg, since the task requires very high physiological cost. During backpack carrying, it is also recommended for a delivery person to make more trips with a light load rather than to make less trips with a heavy load at one trip.