ADDING LOADS TO OCCUPIED WHEELCHAIRS - EFFECT ON STATIC REAR AND FORWARD STABILITY

Objective: To determine the extent to which loads added in different p ositions affect the static rear and forward stability of an occupied w heelchair. Design: Controlled, cross-over study. Intervention: Loads f rom 0 to 10kg (in 1-kg increments) were added to five positions: high rear (HR), low rear (LR, beneath the seat and behind the crossbrace), on the lap (LAP), low anterior (LA, beneath the seat and anterior to t he crossbrace), and on the footrests (FR). We also used a computer mod el to evaluate the relationship between stability and load, with a ran ge of loads (0 to 100kg, in 10-kg increments) beyond the loads that we re practical to test empirically. Outcome Measure: On a tilting platfo rm, we measured the static stability (in degrees) of a wheelchair occu pied by an anthropomorphic test dummy (ATD). Results: The greatest inc rease in rear stability was with FR loads, changes of 64% and 227% for 10-kg and 100-kg loads, respectively. Only HR loads reduced rear stab ility, by 32% and 64%. The greatest increase in forward stability was with LR loads, by 13% and 92%. The greatest reduction in forward stabi lity was with FR loads, by 10% and 149%. To minimize the effect of add ed loads on stability, the LAP and LA positions would be preferred. Co nclusion: Added loads affect wheelchair stability as a function of the load magnitude. The extent and direction of the effect is profoundly influenced by load position. (C) 1996 by the American Congress of Reha bilitation Medicine and the American Academy of Physical Medicine and Rehabilitation .