Open AccessScapular Kinematics and Muscle Activities during Pushing Tasks
Author(s) -
Huang ChunKai,
Siu KaChun,
Lien HenYu,
Lee YunJu,
Lin YangHua
Publication year - 2013
Publication title -
journal of occupational health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 59
ISSN - 1348-9585
DOI - 10.1539/joh.12-0105-oa
Subject(s) - kinematics , scapula , shoulder girdle , physical medicine and rehabilitation , trunk , medicine , physical therapy , trapezius muscle , electromyography , anatomy , physics , biology , ecology , classical mechanics
Scapular Kinematics and Muscle Activities during Pushing Tasks: Chun‐Kai HUANG, et al . Division of Physical Therapy Education, School of Allied Health Professions, University of Nebraska Medical Center, USA—Objectives Pushing tasks are functional activities of daily living. However, shoulder complaints exist among workers exposed to regular pushing conditions. It is crucial to investigate the control of shoulder girdles during pushing tasks. The objective of the study was to demonstrate scapular muscle activities and motions on the dominant side during pushing tasks and the relationship between scapular kinematics and muscle activities in different pushing conditions. Methods Thirty healthy adults were recruited to push a four‐wheel cart in six pushing conditions. The electromyographic signals of the upper trapezius (UT) and serratus anterior (SA) muscles were recorded. A video‐based system was used for measuring the movement of the shoulder girdle and scapular kinematics. Differences in scapular kinematics and muscle activities due to the effects of handle heights and weights of the cart were analyzed using two‐wayANOVAwith repeated measures. The relationships between scapular kinematics and muscle activities were examined by Pearson's correlation coefficients. Results The changes in upper trapezius and serratus anterior muscle activities increased significantly with increased pushing weights in the one‐step pushing phase. The UT/SA ratio on the dominant side decreases significantly with increased handle heights in the one‐step pushing phase. The changes in upward rotation, lateral slide and elevation of the scapula decreased with increased pushing loads in the trunk‐forward pushing phase. Conclusions This study indicated that increased pushing loads result in decreased motions of upward rotation, lateral slide and elevation of the scapula; decreased handle heights result in relatively increased activities of the serratus anterior muscles during pushing tasks.