Effects of load mass and position on the dynamic loading of the knees, shoulders and lumbar spine during lifting: a musculoskeletal modelling approach

The Importance of Lifting Height and Load Mass for Muscular Workload during Supermarket Stocking: Cross-Sectional Field Study

“…In line with multiple previous reports [ 24 , 25 , 33 , 35 , 36 , 37 , 38 , 54 ], our field study also underpins lifting height as an important lifting factor influencing peak muscular workload. Specifically, our data indicated that ‘High’ lifting start and end positions were associated with particularly increased neck/shoulder muscular workload, e.g., lifts from either ‘Low’ or ‘Mod’ start positions to ‘High’ end positions.…”

“…The positive association between load mass and peak muscular workload during un-restricted stocking supports the results of numerous previous laboratory and field studies reporting paralleled increases in load mass and workload of the lower back, knees, and shoulders [ 24 , 25 , 33 , 35 , 36 , 38 , 39 , 54 ]. Using state-of-the-art musculoskeletal models, Skals and colleagues recently demonstrated a clear positive linear relationship between load mass (five kg increments from 5 to 25 kg) and the peak joint reaction forces of the knee and shoulders, as well as the peak compression (L5/S1) and anteroposterior shear forces of the lumbar spine [ 38 ]. Likewise, Plamondon et al reported significantly different peak lumbar spine moments (L5/S1) between lifting objects with load masses of 15 and 23 kg, respectively [ 54 ].…”

“…Specifically, our data indicated that ‘High’ lifting start and end positions were associated with particularly increased neck/shoulder muscular workload, e.g., lifts from either ‘Low’ or ‘Mod’ start positions to ‘High’ end positions. Previous studies assessing outcomes such as glenohumeral joint reaction forces [ 24 , 38 ] and peak EMG activity of the m. deltoideus [ 36 , 37 ] and m. trapezius descendens [ 25 ] have reported similar findings, e.g., higher neck/shoulder workloads at high lifting heights.…”

“…However, the interaction analyses demonstrated that especially lifts performed from ‘Low’ to ‘High’ positions were associated with high low-back muscular workload. Previous studies have demonstrated increased low-back peak workloads (forces/moments) at lower lifting heights compared to higher lifting positions [ 35 , 38 , 54 ]. However, other studies carried out in a supermarket context have also reported surprisingly high peak EMG activity of the low-back when lifts were performed at or to high lifting heights [ 25 , 37 ].…”

“…Multiple biomechanical studies have assessed the influence of certain MMH factors in terms of physical workload, e.g., lifting height [ 32 , 33 , 34 , 35 , 36 , 37 , 38 ] and/or load mass [ 32 , 33 , 34 , 35 , 37 , 38 , 39 ]. However, many of these studies were conducted in laboratories under standardized conditions, which does not capture the complexity as well as intra- and inter-subject variability of un-restricted or real-life work practices.…”