Optimal lifting techniques adopted by Chinese men when determining their maximum acceptable weight of lift

The purpose of this study was to identify biomechanically the mechanisms adopted by Chinese men when they psychophysically determined their MAWLs (maximum acceptable weights of lift) in different tasks. Twenty-two healthy Chinese men determined their MAWLs at two lifting vertical ranges and three lifting frequencies. Peak L5/S1 compressive forces, elbow and shoulder peak reactive moments, acceleration effects, and postures were analyzed throughout the lifting acts. The results showed that different lifting techniques were adopted when determining the MAWL at different vertical ranges and frequencies of lifting. Posture analyses showed that a more stooped technique was used in frequent tasks, which would minimize the metabolic cost. For infrequent tasks, subjects accelerated and lifted the load upward and then shortened the moment arm by flexing the elbow and shoulder joints during landing, to compensate for weakness of the upper extremities. The high prelifting acceleration used during the infrequent tasks caused high compressive forces on the L5/S1 disc. These results emphasize the importance of considering the roles of upper extremity strength when designing lifting tasks for Chinese workers.