Effects of body lean and visual information on the equilibrium maintenance during stance

Abstract

Maintenance of equilibrium was tested in conditions when humans assume different leaning postures during upright standing. Subjects ( n=11) stood in 13 different body postures specified by visual center of pressure (COP) targets within their base of support (BOS). Different types of visual information were tested: continuous presentation of visual target, no vision after target presentation, and with simultaneous visual feedback of the COP. The following variables were used to describe the equilibrium maintenance: the mean of the COP position, the area of the ellipse covering the COP sway, and the resultant median frequency of the power spectral density of the COP displacement. The variability of the COP displacement, quantified by the COP area variable, increased when subjects occupied leaning postures, irrespective of the kind of visual information provided. This variability also increased when vision was removed in relation to when vision was present. Without vision, drifts in the COP data were observed which were larger for COP targets farther away from the neutral position. When COP feedback was given in addition to the visual target, the postural control system did not control stance better than in the condition with only visual information. These results indicate that the visual information is used by the postural control system at both short and long time scales.

Task prioritization in aging: effects of sensory information on concurrent posture and memory performance

“…The length of the ellipse axes were equal to two standard deviations of the COP trajectory along each axis. Within the ellipse approximately 88% of the COP trajectory was fitted, thereby excluding outliers (for details on this method see Oliveira et al 1996;Duarte and Zatsiorsky 2002). Increase in the size of the area covered by the ellipse reflects an increase in postural instability.…”

Revisão sobre posturografia baseada em plataforma de força para avaliação do equilíbrio

“…Body stability in this position is proportional to the base of support area. Figure 2A shows average results of the sway area of the CP, the limits of stability, and the base of support of 13 healthy adults who remained in the quiet erect posture on a force plate for 40 seconds (data obtained by Duarte e Zatsiorsky 23 ). Th us, the increase in the base of support ( feet more distant, Figure 2B) can lead to an increase in the participant' s stability.…”

Percepção de posicionamento articular e do nível de força em sujeitos idosos e jovens

“…Dessa forma, a função visual passa a assumir um papel mais relevante na percepção dos movimentos (ALFIERI, 2008;GAUCHARD et al, 1999;VERSHUEREN et al, 2002). Em adição, estudos que envolvem a quantificação do equilíbrio (DUARTE;ZATSIORSKY, 2002;MANN et al, 2008) GALGANSKI et al, 1993;VAILLANCOURT et al 2003).…”

“…As dificuldades causadas pelos efeitos do envelhecimento em controlar adequadamente os níveis volicionais de força em baixas magnitudes (GALGANSKI;et al, 1993;VAILLANCOURT et al, 2003) independem do segmento testado. No presente estudo, os segmentos inferiores e superiores apresentaram comportamentos bastante similares.…”