<qa>  What is the primary aim of the trial?HIP PRO is a multicenter randomized, controlled trial of an energy absorbing and distributing padding system designed to reduce the incidence of hip fractures in 546 nursing home NH residents. The trial is being conducted in three geographic regions of the US: Boston, St. Louis, and Baltimore. Non bed- or chair-bound residents over the age of 65 are given protective underwear containing a single pocket and hip pad so that each resident becomes hisher own control. During the trial, hip fracture incidence will be compared in padded and unpadded hips using an intent to treat analysis. A secondary aim is to identify resident and facility factors contributing to non-adherence with the use of the hip protector. 