Anticipatory and Reactive Mechanisms of Postural Control in Children and Adolescents
Creators: name: Mills, Richard
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2018
Subjects: Balance
Postural Control
Children
Cerebral Palsy
Virtual Reality
Anchoring Index
Oscillating Platform

description: Maintaining postural control in standing requires the center of mass (COM) to be kept within the boundaries of the base of support (BOS). As the COM moves to a region outside the BOS, a step is often required, increasing the risk of falling, and therefore injury. All too often, humans are subjected to different perturbations while maintaining upright stance, and so to control the COM in these situations, postural activity through musculature at the ankle, knee, and hip are recruited according to demand associated with the level of perturbation. It is also believed that control of the head allows components of the visual and vestibular systems to contribute stable reference values. In order to understand human response to, and in preparation for perturbation, researchers have employed a number of experimental techniques, including i) loading and subsequent unloading of body segments such as the arm or leg; ii) single discrete platform movements; and iii) continuous platform movements. While many studies have focussed on examining postural control mechanisms during discrete perturbations in children and adolescents, these mechanisms in response to continual perturbation have not been well documented in observable developmental stages of youth, nor have they been well documented in special populations. Therefore, the primary aim of this doctoral dissertation was to characterize the reactive and anticipatory postural control mechanisms in children and adolescents, as well as to examine and characterize them in the Cerebral Palsy population. To achieve this overarching goal, three separate studies were performed. The first study characterized the anticipatory and reactive mechanisms of postural control in typically developing children aged 7 to 17 years. Specifically, postural muscle activity in the lower limbs, an index of head anchoring strategy, and body segment cross-correlations were characterized in response to, and in anticipation of, continuous platform oscillation movement at various frequencies. The second experiment characterized these same mechanisms in children of similar ages with cerebral palsy, and compared the results to those found in the first study. The results of these studies indicated a slight shift to anticipatory measures after repeated exposure to a specific frequency of platform oscillation, however, each transition to a greater platform speed resulted in more conservative measures of postural control. Furthermore, youth with cerebral palsy tended to control their posture much in the same way of typically developing children and adolescents under less challenging conditions however, with the increased difficulty associated with higher frequency oscillation were not able to generate adequate postural responses. The final study in this dissertation investigated the effects of a one-week intensive virtual reality-based exercise programme. In this study, postural control mechanisms were observed before and after a one-week time period, during which half of the participants received the enhanced exercise while the remaining participants received no treatment at all. The results from this study indicated there was no effect of a 5-day VR-based intervention on postural control mechanisms used in response to oscillating platform perturbations. Taken together, the results from these studies extend the current understanding of reactive and anticipatory mechanisms of postural control in children and adolescents, both typically developing and those with cerebral palsy.