Effects of height and load weight on shoulder muscle work during overhead lifting task

Abstract

Few musculoskeletal models are available to assess shoulder deeper muscle demand during overhead lifting tasks. Our objective was to implement a musculoskeletal model to assess the effect of lifting height and load on shoulder muscle work. A musculoskeletal model scaled from 15 male subjects was used to calculate shoulder muscle work during six lifting tasks. Boxes containing three different loads (6, 12 and 18 kg) were lifted by the subjects from the waist to shoulder or eye level. After optimisation of the maximal isometric force of the model's muscles, the bio-fidelity of the model was improved by 19%. The latter was able to reproduce the subjects' lifting movements. Mechanical work of the rotator cuff muscles, upper trapezius and anterior deltoid was increased with lifting load and height augmentation. In conclusion, the use of a musculoskeletal model validated by electromyography enabled to evaluate the muscle demand of deep muscles during lifting tasks.

Validity of Wearable Sensors at the Shoulder Joint: Combining Wireless Electromyography Sensors and Inertial Measurement Units to Perform Physical Workplace Assessments

“…During arm elevation, shoulder muscles are highly requested to maintain joint stability, and having an adequate muscle activation pattern plays a major role in the prevention of injuries [18]. To the best of our knowledge, only two studies have identified the effects of arm elevation and weight lifting on muscle activation during simulated working tasks [19,20]. However, the effect of shoulder range of motion was not accounted for, which can be an important contributing factor to shoulder pain of manual handling workers.…”

Muscle function in glenohumeral joint stability during lifting task

“…We used an OpenSim generic model of the shoulder adapted to lifting task investigation (fully described in [ 9 ]) which was based on a combination of previous Opensim models [ 31 – 33 ]. Briefly the model was composed of 9 segments and 22 degrees-of-freedom and actuated by 22 muscle-tendon units (including 47 lines of actions with the muscle properties described in [ 34 ]) and 22 residual torque actuators (i.e.…”

“…The generic model was scaled to match each subject’s anthropometry using the experimental positions of the skin markers during a static pose. In addition, muscle maximal isometric forces were optimized for each subject-scaled-model by minimizing the difference between the normalized EMG and simulated muscle activations obtained during the lifting movement according to the method developed by Blache et al [ 9 ].…”

“…Especially, Escamilla et al [ 8 ] pointed out that the activation of the anterior deltoid may cause a translation of the humeral head and consequently reduce the stability of the glenohumeral joint. Therefore, movements such as lifting task for which middle and anterior deltoids are the main prime movers [ 9 , 10 ] may be subject to glenohumeral instability.…”

“…Therefore, this study aimed to assess the stabilization function of the shoulder muscles in a healthy population during a lifting task. This repetitive task, usually performed in manufactory industry, may result in glenohumeral instability because of the main activation of the anterior and middle deltoids [ 9 , 10 ]. We hypothesized that the glenohumeral stability constraint led to a greater force produced by the rotator cuff muscles and the latissimus dorsi in comparison to the condition without stability constraint.…”