Adriana M. Degani

Is Voluntary Control of Natural Postural Sway Possible

The authors explored whether standing human participants could voluntarily decrease the amplitude of their natural postural sway when presented with explicit visual feedback and a target. Participants (N = 9) stood quietly, without any feedback and with feedback on the center of pressure coordinate or the head orientation. They were unable to decrease sway amplitude when presented with visual feedback and a target. Decreasing target size led to contrasting effects on the 2 fractions of sway: rambling and trembling. The smaller target was associated with a decrease in rambling and an increase in trembling. Those observations suggest that sway represents a superposition of at least 2 independent processes. They also suggest that providing visual feedback on a variable tied to body sway may not be an effective way to decrease postural sway in young healthy people.

The effects of early stages of aging on postural sway: A multiple domain balance assessment using a force platform

Technical advancements in instrumentation and analytical methods have improved the ability of assessing balance control. This study investigated the effects of early stages of aging on postural sway using traditional and contemporary postural indices from different domains. Eleven healthy young adults and fourteen healthy non-faller older adults performed two postural tasks: (a) functional limits of stability and (b) unperturbed bipedal stance for 120s. Postural indices from spatial, temporal, frequency, and structural domains were extracted from the bodys center of pressure (COP) signals and its Rambling and Trembling components. Results revealed a preservation of functional limits of upright stability in older adults accompanied by larger, faster, and shakier body sway in both anterior-posterior and medio-lateral directions; increased medio-lateral sway frequency; increased irregularity of body sway pattern in time in both directions; and increased area, variability, velocity, and jerkiness of both rambling and trembling components of the COP displacement in the anterior-posterior direction (p<0.02). Such changes might be interpreted as compensatory adjustments to the age-related decline of sensory, neural, and motor functions. In conclusion, balance assessment using postural indices from different domains extracted from the COP displacement was able to capture subtle effects of the natural process of aging on the mechanisms of postural control. Our findings suggest the use of such indices as potential markers for postural instability and fall risk in older adults.

Upright balance control strategies during pregnancy

BACKGROUND Morphological and physiological changes during pregnancy are considered to interfere with the mechanisms of postural control and potentially increase the risk of falling. A clear understanding of these mechanisms is important to improve pre-natal care and reduce the fall risk in this population. OBJECTIVES This study focused on investigating how pregnancy affects postural control in each trimester of pregnancy by analyzing pelvic inclination and body sway behavior. Our main hypothesis was that balance control and posture would change during pregnancy. More specifically, pregnancy would increase sway amplitude, anterior pelvic tilt, and body sway regularity in time. STUDY DESIGN Forty women formed four groups: non-pregnant women (NP) and women at their first, second, and third trimester of pregnancy (P1, P2, and P3, respectively). All participants performed (1) postural evaluation of the pelvic inclination using a digital system of postural analysis and (2) instrumented posturography using a force platform to collect the coordinates of the bodys center of pressure (COP) during quiet bipedal stance for 120 s. Kruskal-Wallis H test and post-hoc Mann-Whitney U tests were used to investigate the effects of pregnancy (NP, P1, P2, and P3) on pelvic inclination angle and postural indices computed from the COP signals. RESULTS Results revealed significant larger body sway accompanied by a more regular medial-lateral pattern of oscillation and a more synchronized anterior-posterior and medial-lateral sway already at the first trimester of pregnancy. The averaged COP migrated posteriorly at third trimester of pregnancy and the anterior pelvic tilt increased at second and third trimesters. CONCLUSIONS Our results indicate the existence of changes in posture and balance metrics even at early stages of pregnancy. We suggest the use of posturography as one of screening tools for postural instability and fall risk during pregnancy.