The invention relates to a method for use in constructing a garment (25) including elastic, in a processing system, as one of a series of consecutive workpieces in a continuous web, the workpieces having front and back body portions separated by a crotch portion, the method including, with respect to respective workpieces, the steps of: (a) stretching an elastic (b) incorporating the stretched elastic into the continuous web in stretched condition and (c) subsequently relieving stretch in the elastic at the crotch portion of each respective workpiece in the web, while maintaining the stretch in the elastic at the front and back body portions of each respective workpiece, by applying ultrasonic energy to the outer surface of the workpiece at at least one selected locus at the crotch portion, sufficient to effect severing of the elastic without corresponding severing of the continuous web. Furthermore, the invention relates to a respective processing system.
