The effect of on-body lift assistive device on the lumbar 3D dynamic moments and EMG during asymmetric freestyle lifting

A new on-body personal lift assistive device was developed to reduce back muscles force requirements during asymmetric repetitive lifting task. The positions and orientations of 10 upper body segments of nine male subjects were recorded by Fastrak (TM). Left and right thoracic and lumbar erector spinae, external obliques, and rectus abdominis were normalized to maximum and integrated EMG of the and were compared in asymmetrical lifting for three different loads (5kg, 15kg, 25 kg) using free style under two conditions of with and without the device. The assistive device significantly reduced the required muscular effort of the lumbar and thoracic erector spinae (p=0.001) with no significant differences in the level of abdominal muscular activity. Group iEMG amplitudes were reduced by 23.9% for lumbar erector spinae, 24.4% for thoracic erector spinae and 34.9% for the contralateral external oblique muscles.