Superficial shoulder muscle co-activations during lifting tasks: Influence of lifting height, weight and phase

Type de document

Études primaires

Année de publication

2015

Langue

Anglais

Titre de la revue

Journal of Electromyography and Kinesiology

Première page

355

Dernière page

362

Résumé

This study aimed to assess the level of co-activation of the superficial shoulder muscles during lifting movement. Boxes containing three different loads (6, 12, and 18 kg) were lifted by fourteen subjects from the waist to shoulder or eye level. The 3D kinematics and electromyograms of the three deltoids, latissimus dorsi and pectoralis major were recorded. A musculoskeletal model was used to determine direction of the moment arm of these muscles. Finally an index of muscle co-activation named the muscle focus was used to evaluate the effects of lifting height, weight lifted and phase (pulling, lifting and dropping phases) on superficial shoulder muscle coactivation. The muscle focus was lower (more co-contraction) during the dropping phase compared to the two other phases (−13%, p < 0.001). This was explained by greater muscle activations and by a change in the direction of the muscle moment arm as a function of glenohumeral joint position. Consequently, the function of the shoulder superficial muscles varied with respect to the glenohumeral joint position. To increase the superficial muscle coactivation during the dropping phase may be a solution to increase glenohumeral joint stiffness.

Mots-clés

Épaule, Shoulder, Soulèvement des charges, Manual lifting, Poids maximal des charges à porter, Maximum acceptable weight of lift, Appareil locomoteur, Musculoskeletal system, Force musculaire, Muscular strength

Numéro de projet IRSST

2010-0024

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