Net shoulder joint moment and muscular activity during light weight handling at different heights and frequencies.

Ten (10) normal adult male subjects were asked to move a known weight, representing 15% of the maximal lifted weight, in both horizontal and vertical conditions at frequencies of 40 cycles/min and 60 cycles/min. Raw EMG signals from six (6) shoulder muscles were recorded and synchronized with the cinematographic data during three (3) trials of six (6) seconds each. The raw EMG signals of each muscle were full wave rectified and filtered at three (3) Hz. The LE EMG signals were normalized by time (% cycle) and by amplitude (% MVC), and for the analysis of variance, the normalized LE EMG signals were integrated (IN LE EMG). The average shoulder angular velocities, joint moments and moment powers were computed from cinematographical data. No significant difference were observed between both tasks for the supraspinatus, infraspinatus, and pectoralis major IN LE EMG data as well as for integrated normalized shoulder joint moment for the whole cycle of movement. IN LE EMG data from middle deltoid, anterior deltoid, and trapezius muscles were significantly higher (p 0.05) when performing the vertical displacement task for the whole cycle of movement. (Abstract shortened by UMI.