Similarities and differences in automatic balance reactions to platform translations between individuals with stroke and healthy controls

Purpose. The purpose of this study was to: (1) determine the presence of automatic balance reactions based on the pattern of the total body center of mass (TBCM) displacement in individuals post-stroke and healthy age-matched controls during platform translations at varying degrees of difficulty (varying velocities) and; (2) identify the movement strategies by which balance was restored.; Subjects. Nine healthy, age-matched controls and 18 individuals with a single stroke who had completed a rehabilitation program were enrolled.; Methods. Subjects were randomly translated forward (FT) and backward (BT) at 3 velocities over 4 trials. While standing independently on a moveable platform. The x and co-ordinates of body markers of the subjects were digitized from video recordings. TBCM displacement and angular displacement about the ankle, knee and hip/trunk (HT) were calculated. Each individual's performance per translation was graded as good, fair, poor or fall dependent on the onset and pattern of the TBCM. The timing and magnitude of ankle, knee and HT movements were analyzed. EMG recordings from bilateral tibialis anterior (TA), gastrocnemius (GA), hamstrings (HA) and quadriceps (QU) were band-pass filtered at 10 Hz to 3 Khz, rectified and low-pass filtered at 50 Hz. Fugl-Meyer lower extremity and balance tests were done with each stroke subject.; Results. The presence of automatic balance responses was determined for all groups by the presence of angular displacements, by the onset of muscle activity and by the number of successful performance grades for the TBCM displacement. Success for FT was less than BT for all groups. Stereotypical and distinct movement patterns were identified for FT and for BT. Significant differences between controls and the 2 stroke groups were present in timing and pattern of the responses. The RCVA group performed significantly better than the LCVA group. The Fugl-Meyer scales did not correlate with performance grades. (Abstract shortened by UMI.)...