Abstract
Musculoskeletal disorders (MSDs) are still common problems in the workplace. In this study, we focus on the posture of squat, one of the postures been shown to be strongly associated with MSDs. This research aims to develop a squat assistance tool and evaluate its influences at the lower limbs when participants wear the proposed squat assistance tool with different angles in performing a task using squatting posture. Ten males and ten females participated in this study. Two independent variables were tested in this study, the angle of assistance tool (0°: assistance tool was not used, 7.5°, 15°)and the squatting posture (full squat and full squat with one knee close to the ground). Each participant completed a total of 6(3x2) trials. In each trial, the participant moved along with at a constant pace (every 20 seconds) and fixed step length (30cm each step) for a total of 150 seconds. The electromyography (EMG) was used as a measure of activity level of the lower limbs. The joint coordination data were collected by a motion tracking system to calculate the joint angles. By the end of trial, each participant was asked to fill out a questionnaire about his/her subjective feelings. The results showed that use of assistance tools during squatting can reduce the fatigue. When adopting the posture of full squat with one knee close to the ground, the use of the 7.5°assistance tool can significantly decrease about 12.45% of the %RVC value of right rectus femoris (RRF). While adopting the posture of full squat, the use of the 15°assistance tool can significantly decrease 19.23% of the %RVC value of right rectus femoris (RRF). Keywords: musculoskeletal disorder, squatting, assistance tool, EMG, joint angle