Publication Type:Book Chapter
Source:Posture, Balance and the Brain, International Workshop Proceedings, p.22-28 (2015)
Keywords:center of pressure, postural sway, sensory integration, suprapostural task
Adequate integration of sensory information from different modalities is essential for standing balance. Inadequate and/or incongruent information inputs cause sensory conflict which endangers equilibrium. That is even more expressed during dynamic suprapostural tasks, such as functional reach (FR). Our aim was to study the influence of sensory conflict on FR performance and dynamic standing balance steadiness. Ten healthy right-handed adults per-formed FR standing on a pedobarographic platform in four sensory conditions: eyes-open (EO), eyes-closed (EC), head in maximal extension and eyes open or closed (EO-HE/EC-HE), adding conflict of vestibular origin. Data were analyzed by Two-Way RM Anova and paired t-test. Factor vision was significant, while only a tendency for head position was found for FR, which shortens in EC, EO-HE and especially EC-HE. For center of pressure (COP) sway path both vision and head position were significant factors. Sway path increased in both EC conditions compared to EO, respectively. Head extension also increased sway path, differences were found between EC and EC-HE. The longest sway path was in EC-HE. Only vision was significant for medio-lateral (M-L) COP sway, which increased in EC compared to EO, respectively. Again, the greatest sway was in EC-HE. The increased COP sway path and M-L sway correspond with decreased FR performance. All these results suggest that absence of vision and/or inadequate vestibular information input, deteriorate dynamic standing balance and task performance, which is expressed the most when both sensory modalities are affected. Factor head position was significant for forward and backward COP velocities (when subjects reach forward and return to initial position). For forward velocity there was significant diminution only between EC-HE and EO, for backward velocity – between EO and both HE conditions. These results suggest that altered vestibular information probably causes velocity decrease. Accuracy of return from FR to initial COP position was greater in EC than in EO. This may be explained by increased weight of proprioception in absence of visual information and/or increased confidence in its presence. Our study suggests a correlation between balance steadiness and suprapostural task performance during sensory conflict. Absence of vision has more impact than altered vestibular information in all cases but for the decrease in FR task dynamics.