An investigation into the effect of the trajectory shape on resulting arm vibrations is presented based on the concept of the shock spectrum. A method to obtain trajectories whose shock spectrum has prescribed properties is briefly described, and some preliminary results are presented. A comparison of various trajectory planning algorithms, in terms of their effectiveness in reducing residual vibrations and the move time, is given. Two performance indices are defined to quantify the information obtained through the shock spectrum and the move time analysis. The superiority of a trajectory based on the simultaneous minimization of the time of travel and residual response is illustrated.