EFFECTS OF INCREASED INERTIAL LOAD IN DYNAMIC AND RANDOMIZED PERTURBED POSTUROGRAPHY

Muscular weakness is present in many diseases. The present study attem pted to model a relative weakness of postural control muscles by loadi ng the subjects with extra weight, and the effects on EquiTest dynamic posturography and randomized perturbed posturography were assessed. T en healthy subjects aged 15-39 years (mean 26 years) were used. Their weights ranged 53-82 kg. Equilibrium was measured with and without an extra 20% of body weight attached to the upper part of the trunk by me ans of pieces of lead metal placed in a specially sewn shirt. Dynamic posturography (EquiTest) comprises a sensory organization test in whic h the support surface and visual surround are either stable or referen ced to the patient's sway, his or her eyes open or closed. In a moveme nt coordination part the platform makes active movements. Antero-poste rior sway on a stable support surface with absent or distorted visual cues was marred, and the correction pattern was altered on a movable s upport surface when the vision was absent. Furthermore, the EquiTest a pparatus was driven by special software to produce randomized antero-p osterior movements during 45 s. In addition to stable conditions, smal l and large amplitude perturbations were used. The subject's ability t o remain in equilibrium was estimated by the sway velocity and a confi dence ellipse sway area during 45 s. During weightbearing, sway areas were larger on the stable support surface both with and without vision . Postural sway velocity was lower when vision was absent both using s mall and large amplitudes. In conclusion, increased inertial load dete riorates balance on a stable support surface both with and without vis ion, and makes postural corrections slower when the environment is act ively moving in absence of vision.