Demanda supra-postural em tarefas de ancoragem háptica afeta a estabilidade postural?
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Data
2018-09-18
Autores
Magre, Fernanda Lopes [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Os sistemas sensoriais e motor trabalham de forma integrada para restabelecer o equilíbrio corporal durante a realização de outras tarefas (e.g., carregar uma bandeja com copos, trocar uma lâmpada enquanto equilibramos numa escada, etc.), as quais identificamos como “supra-posturais”. Ainda, indivíduos usam a percepção háptica para incorporar ferramentas na realização dessas tarefas que podem, concomitantemente, auxiliar no controle da postura. Uma ferramenta identificada como útil ao controle postural é o sistema âncora que consiste numa tarefa de manipular sutilmente cabos flexíveis anexos a cargas de reduzida massa que ficam em contato com o solo. Segurando a ponta desses cabos com as mãos, os indivíduos, via exploração ativa do sistema háptico, ajustam seu corpo no espaço mais eficientemente do que sem esta ferramenta. O objetivo desse estudo é analisar em tarefa de ancoragem háptica como componentes de tarefa supra-postural (i.e., deslocar o sistema âncora ritmicamente para cima e para baixo; com e sem contato com o solo e com e sem presença de cargas anexas ao sistema âncora) afetam os níveis de oscilação corporal em tarefas de equilíbrio. Participaram do estudo 15 adultos jovens que realizaram duas sessões de coleta em dias distintos (sessão de ancoragem com cargas e sessão de ancoragem sem cargas). Os participantes ficaram em pé sobre uma plataforma de força com os pés na posição tandem, vendados, durante 30 segundos, e, ao som de um metrônomo (55 BPM), levantaram e abaixaram ritmicamente o sistema âncora (i.e., com cargas anexas) ou cabos de nylon livres (i.e., sem cargas anexas) de acordo com as seguintes condições: ancoragem estática, ancoragem dinâmica em fase, ancoragem dinâmica fora de fase e ancoragem mista. As mesmas condições foram realizadas nas duas sessões de ancoragem. Para cada condição foram realizadas 2 tentativas. As variáveis do centro de pressão (COP) incluíram o comprimento total do COP (CT-COP), RMS do deslocamento médio-lateral (RMS-ml), velocidade média de oscilação médio-lateral (Velocidade-ml) e frequência com 80% da potência espectral na direção médio-lateral (F80-ml). Os resultados revelaram que um sistema de ancoragem sem cargas não promove efeitos estabilizadores na postura, o que não o caracteriza como uma tarefa predominantemente supra-postural. Ainda, manter as cargas em suspensão durante uma tarefa de ancoragem não promove efeitos estabilizadores na postura tal como ocorre ao manter as cargas em contato com o solo. Por fim, ancorar-se com cargas estáticas no solo promove efeitos estabilizadores para a postura melhores do que ancorar-se com cargas de forma dinâmica. Esses resultados demonstram a influência da informação sensorial para controlar a postura em um sistema de ancoragem háptica, que depende de uma referência fixa para orientação postural (i.e., cargas das âncoras em contato com uma superfície).
The sensory and motor systems work in an integrated way to reestablish balance while performing other motor tasks (e.g., carry a tray with cups, changing a light bulb while balancing on a ladder, etc.), which we identify as “supra-postural.” Moreover, individuals use haptic perception to control tools while performing these tasks that can, at the same time, aid the postural control system. A tool identified as useful to the postural function is the anchor system, which consists in subtle manipulation of flexible cables attached to low mass loads that are kept in contact with the ground. Holding these cables with their hands, individuals, via active exploration, adjust their bodies in space more efficiently than without this tool. The purpose of this study is to analyze in haptic anchorage tasks how does supra-postural components (e.g., intentionally move rhythmically the anchor system up and down; with or without anchor masses touching the ground, and with or without the end loads attached to the anchor system) affect body sway during balancing tasks. Fifteen young adults participated in this study in two sessions of data collection separated in two different days (anchors with loads and free-load anchors). The participants stood on a force platform with their feet in tandem position, blindfolded, for 30 seconds. To the sound of a metronome (55 BPM), they moved anchor system or the nylon strings (e.g., without the attached loads) up and down according to the following conditions: quiet anchoring, in-phase and out-of-phase dynamic anchoring, and mixed anchoring (e.g., one hand quiet anchoring while the other keep a dynamic anchoring). The variables of the center of pressure (COP) included the COP’s path length (PL-COP), ellipse area, RMS of medial-lateral displacement (RMS-ml), mean speed of medial-lateral oscillation (MSS-ml) and the frequency at 80% of the power spectrum (F80-ml). Our results revealed that an unloaded anchorage system does not provide stabilizing effects for the posture system and is not characterized as a supra-postural task, contrary to the anchor system with loads. Also, keeping the loads in suspension during an anchoring task does not stabilize posture as much as when keeping the loads in contact with the ground. Finally, anchoring with steady loads on the ground promotes stabilizing effects of the posture compared to dynamic anchoring with loads moving rhythmically. These results illustrate that sensory information to control posture during haptic anchoring tasks rely on a fixed reference for postural orientation (i.e., anchor loads in contact with a surface).
The sensory and motor systems work in an integrated way to reestablish balance while performing other motor tasks (e.g., carry a tray with cups, changing a light bulb while balancing on a ladder, etc.), which we identify as “supra-postural.” Moreover, individuals use haptic perception to control tools while performing these tasks that can, at the same time, aid the postural control system. A tool identified as useful to the postural function is the anchor system, which consists in subtle manipulation of flexible cables attached to low mass loads that are kept in contact with the ground. Holding these cables with their hands, individuals, via active exploration, adjust their bodies in space more efficiently than without this tool. The purpose of this study is to analyze in haptic anchorage tasks how does supra-postural components (e.g., intentionally move rhythmically the anchor system up and down; with or without anchor masses touching the ground, and with or without the end loads attached to the anchor system) affect body sway during balancing tasks. Fifteen young adults participated in this study in two sessions of data collection separated in two different days (anchors with loads and free-load anchors). The participants stood on a force platform with their feet in tandem position, blindfolded, for 30 seconds. To the sound of a metronome (55 BPM), they moved anchor system or the nylon strings (e.g., without the attached loads) up and down according to the following conditions: quiet anchoring, in-phase and out-of-phase dynamic anchoring, and mixed anchoring (e.g., one hand quiet anchoring while the other keep a dynamic anchoring). The variables of the center of pressure (COP) included the COP’s path length (PL-COP), ellipse area, RMS of medial-lateral displacement (RMS-ml), mean speed of medial-lateral oscillation (MSS-ml) and the frequency at 80% of the power spectrum (F80-ml). Our results revealed that an unloaded anchorage system does not provide stabilizing effects for the posture system and is not characterized as a supra-postural task, contrary to the anchor system with loads. Also, keeping the loads in suspension during an anchoring task does not stabilize posture as much as when keeping the loads in contact with the ground. Finally, anchoring with steady loads on the ground promotes stabilizing effects of the posture compared to dynamic anchoring with loads moving rhythmically. These results illustrate that sensory information to control posture during haptic anchoring tasks rely on a fixed reference for postural orientation (i.e., anchor loads in contact with a surface).
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Palavras-chave
Sistema âncora, Supra-postural, Percepção háptica, Anchor system, Haptic perception