The effect of single-handed lifting tasks on the activation of the neck-shoulder shared musculature

Abstract

The use of the hand in lifting has been linked to occupational injuries of the neck and shoulder. This research is aimed at examining the effect of work-related factors on the major neck-shoulder shared musculature activity on both sides of the cervical spine for a right-handed lifting task. Subjects lifted different weights from 20 different locations produced by the interaction of varying heights, reach distance, and angles simulating the work done by assembly line workers. All lifting tasks were done by the right hand. Bilateral electromyography data of major shared musculature (upper trapezius, sternocleidomastoid, and levator scapula) were collected using surface EMG electrodes. Analyses demonstrate that work-related factors; hand weights, reach distance, angles, and gender significantly affect the activation level of active shared musculature of the neck. Results also showed that the active shared musculature (the right side) has a significant influence on the activation of the antagonistic shared musculature. The findings show that reducing the weights being handled and keeping work area closer to the body reduces the muscle activities in the shared muscles. These findings may be used to build a biomechanical model to predict the compressive forces acting on the cervical spine due to one hand lifting.

Keywords:

• Electromyography
• maximum voluntary contraction
• shared musculature
• cervical spine
• musculoskeletal disorders