Trunk muscles play an important role during load lifting and contract to control trunk stability. The aim of present study was to investigate immediate effects of using various insole wedges on activation and cocontraction indices of selected trunk muscles during load lifting. Thirty able-bodied males completed load lifting task using nine various insole wedges. The results showed these significant differences: for normalized mean amplitude of RA muscle between posterior and anterior-medial wedges and for QL muscle between posterior and lateral wedges, for normalized peak amplitude of RA muscle between posterior and anterior-medial wedges, for median frequency of LES muscle between anterior-medial and anterior-lateral wedges, and for co-contraction of RA/TES, RA/LES and RA/MU between posterior and anterior-medial wedges (P ¼ 0.001). These findings should be considered during designation of shoe or insole for work environments. Future studies need to assess other biomechanical aspects of using various insole wedges during work-related tasks.
