A test of the rambling and trembling hypothesis: multiple sclerosis and postural control.

The rambling-trembling analysis of postural control maintains that the center of pressure (COP) trajectory can be decomposed into deviations resulting from supraspinal (i.e., rambling; RM) and spinal processes (i.e., trembling; TM). The purpose of this investigation was to test the rambling and trembling hypothesis by comparing persons with multiple sclerosis (MS) who had either elevated or normal spinal reflexes to healthy controls. 16 subjects with MS and 16 age and gender matched control subjects completed a postural control task. The persons with MS were divided into groups with high (MShigh) or low (MSlow) H-reflex amplitude. The MShigh group had an elevated ratio of TM to COP compared with healthy controls, but no differences in the ratio between RM and COP. The findings are congruent with the assumptions of the rambling-trembling hypothesis. Further work is needed to determine if RM and TM represent distinct spinal and supraspinal mechanisms to postural control.