Physiological workload evaluation of carrying soft drink beverage boxes on the back

Soft drink manufacturing has become one of the largest food industries in Korea, now competing in a 2.5-billion dollar market, with more than 20,000 people employed. Deliveries of a broad line of soft drink products involve the use of a hand truck and, in many cases, a backpack mode of carriage. Workers usually prefer the backpack mode, because they feel safer by carrying beverage boxes on the back on stairs. In this study, the physiological workload involved in backpack-mode carrying was investigated, especially focusing on the effects of load weight and stairway transport. To measure heart rate and oxygen uptake while carrying on the back, a laboratory experiment was conducted and safety guidelines for such tasks were proposed, based on the experimental results. Eight healthy male subjects performed backpack-mode carrying, weight between 40 and 60 kg: (1) on level ground, (2) upstairs and (3) downstairs. The results showed that stairways involved an increased physiological burden, and that a load of 60 kg entailed a significantly higher physiological cost than carrying a load of 40 kg. Although backpack-mode carrying has some biomechanical advantages, the worker should be advised to carry a load of less than 40 kg, to avoid a high physiological load. During backpack-mode carrying, it is also recommended that a delivery person makes more trips with a light load rather than fewer trips with a heavier load per trip.