How does body height affect the postural movement structure in bipedal and tandem stance?

Aim: The purpose of this study is to investigate differences how body-height could influence movement structure, during different balance tasks, and how this variable affects the variables associated with postural control. Methods: Eighteen healthy male subjects participated in this study, divided in two height groups, one >1,80m, and the second group >1,90 m. Participants were evaluated on five different trials, three in bipedal stance and two in tandem stance. Kinematic data were collected through the Vicon motion tracking system, and the centre of pressure (COP) motion was recorded using a ground AMTI force plate. In order to detect the principal movements responsible for balance and to evaluate postural control a principal component analysis (PCA) was computed. Statistical analysis was separately conducted for PCA and COP. Variables considered for PCA were: relative subject specific variance (PP_rVAR (%)), Principal Velocity variance (PV_rVAR), Number of Zero Crossings (PA_NoZC); for CoP : Trajectory mean velocity (COP_MV), Ellipse area 95% (COP_EA) Anterior-posterior excursion (COP_Rap) and Medio-lateral excursion (COP_Rml). Results: The first five PM explained more than >99% of the movements. A significant group effect was found in bipedal PV1_rVAR(p = 0.000) and PV2_rVAR ( p = 0.000) and PA2 (p = 0.038). For the COP motion only in normalized COP_MV ( p = 0.045), a group effect was observed. In tandem trials, PCA revealed significant group effect in PP5 (p = 0.027), PV2 (p = 0.028), PV3 ( p = 0.046) and PV5 (p = 0.017) and COP data analysis only in not-normalized results COP_MV ( p = 0.010), COP_EA (p = 0.016) and in COP_Rml (p = 0.015). Significant main trial effect and interaction effect between group and trial were displayed for several variables. Discussion: In the data processing the normalization method mitigated the influence of the subjects anthropometric characteristics, but ensured a quality data comparison (Federolf, 2016). Height affected the velocity of posture changes, the 1,90 group. An increase of task difficulty is associated with an increase in body sway, (Kiemel et al., 2002), eyes closed trials and dual tasking tried to challenge participants balance in different stances. This will favour the prioritized task as the nervous system will delay information processing related to the non-prioritized task and therefore the performance for this task could be reduced (Fraizer & Mitra, 2008). Conclusion: PCA in bipedal and tandem trials showed a group effect in the velocity of posture changes (PV_rVAR). The other variables considered revealed similar balance control for both groups, normalization factor is partly responsible. In COP analysis, a group effect in the not-normalized data, emerged, free from normalization.Arbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprüftInnsbruck, Univ., Masterarb., 2019(VLID)452823