Work experience at height suppressed the effect of dynamic visual input on postural sway when static visual cues were visible (original) (raw)
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This paper discusses the impact of vision on balance and orientation in patients with vestibular disorders and in anxiety patients with space and motion discomfort (SMD). When the vestibular system is impaired, vision has a greater influence on standing postural control, resulting in greater sway when individuals are presented with erroneous or conflicting visual cues. Studies have shown that individuals with other motion sensitivities, such as motion sickness, also tend to rely on vision for balance and do not disregard erroneous visual cues. Recently, patients with anxiety disorders that include SMD also have been shown to have increased postural sway in conflicting visual environments, similar to patients with vestibular disorders. Thus, while specific vestibular deficits are not always directly associated with SMD, data regarding the impact of vision on balance suggest that some patients with SMD may have an underlying balance disorder.
Quality of Visual Cue Affects Visual Reweighting in Quiet Standing
PLOS ONE, 2016
Sensory reweighting is a characteristic of postural control functioning adopted to accommodate environmental changes. The use of mono or binocular cues induces visual reduction/ increment of moving room influences on postural sway, suggesting a visual reweighting due to the quality of available sensory cues. Because in our previous study visual conditions were set before each trial, participants could adjust the weight of the different sensory systems in an anticipatory manner based upon the reduction in quality of the visual information. Nevertheless, in daily situations this adjustment is a dynamical process and occurs during ongoing movement. The purpose of this study was to examine the effect of visual transitions in the coupling between visual information and body sway in two different distances from the front wall of a moving room. Eleven young adults stood upright inside of a moving room in two distances (75 and 150 cm) wearing a liquid crystal lenses goggles, which allow individual lenses transition from opaque to transparent and vice-versa. Participants stood still during five minutes for each trial and the lenses status changed every one minute (no vision to binocular vision, no vision to monocular vision, binocular vision to monocular vision, and vice-versa). Results showed that farther distance and monocular vision reduced the effect of visual manipulation on postural sway. The effect of visual transition was condition dependent, with a stronger effect when transitions involved binocular vision than monocular vision. Based upon these results, we conclude that the increased distance from the front wall of the room reduced the effect of visual manipulation on postural sway and that sensory reweighting is stimulus quality dependent, with binocular vision producing a much stronger down/up-weighting than monocular vision.
How attentional focus on body sway affects postural control during quiet standing
Psychological Research, 2007
The purpose of this study was to investigate how attentional focus on body sway affects postural control during quiet standing. To address this issue, sixteen young healthy adults were asked to stand upright as immobile as possible on a force platform in both Control and Attention conditions. In the latter condition, participants were instructed to deliberately focus their attention on their body sways and to increase their active intervention into postural control. The critical analysis was focused on elementary motions computed from the centre of pressure (CoP) trajectories: (1) the vertical projection of the centre of gravity (CoG v) and (2) the difference between CoP and CoG v (CoP-CoG v). The former is recognised as an index of performance in this postural task, whilst the latter constitutes a fair expression of the ankle joint stiffness and is linked to the level of neuromuscular activity of the lower limb muscles required for controlling posture. A frequency-domain analysis showed increased amplitudes and frequencies of CoP-CoG v motions in the Attention relative to the Control condition, whereas non-significant changes were observed for the CoG v motions. Altogether, the present findings suggest that attentional focus on body sway, induced by the instructions, promoted the use of less automatic control process and hampered the efficiency for controlling posture during quiet standing.
Relative efficacy of various strategies for visual feedback in standing balance activities
Experimental Brain Research, 2013
Seventy-nine young, healthy adults were led through static balance and weight-shifting activities in order to study the effects of visual feedback on balance. Based on their performance, the relative effects of various feedback properties were analyzed: 1) arrangement (direct center of pressure (CoP) vs. lateral weight distribution feedback), 2) numbers (presence or absence of numeric feedback), and 3) dimensionality (1-D vs. 2-D CoP information). In the static balance activity, subjects were instructed to maintain equal weight across both feet; in the dynamic weightshifting activity, subjects were instructed to shift their weight to each displayed target location. For static balance, lateral symmetry and sway were measured by classical parameters using CoP, center of gravity (CoG), and the difference between the two (CoP-CoG). Weight-shifting balance performance was measured using the time required to shift between target CoP positions. Results indicated that feedback arrangement had a significant effect on static sway and dynamic weight shifting, with direct CoP feedback resulting in better balance performance than lateral weight distribution. Also, numbers had a significant effect on static sway, reducing lateral sway compared to feedback without numbers. Finally, 2-D CoP feedback resulted in faster performance than 1-D CoP feedback in dynamic weight shifting. These results show that altering different properties of visual feedback can have significant effects on resulting balance performance; therefore, proper selection of visual feedback strategy needs to take these effects into consideration.
Aging and Postural Control: Postural Perturbations Caused by Changing the Visual Anchor
Journal of the American Geriatrics Society, 1999
OBJECTIVE: To determine the effect of modifying the stable visual anchor on the postural stability of older individuals. The visual anchor was changed by opening doors similar to those found in an elevator cage. Lighting intensities inside and outside the cage were varied to create increasing or decreasing luminosity conditions. The effect of adding a cognitive load (counting backwards) was also tested. DESIGN A controlled laboratory study. SETTING: Tests performed in a balance laboratory. MEASUREMENTS: Sensory and clinical measurements to insure the integrity of the central and peripheral nervous system. Measures of balance were derived from the recordings of the center of foot pressure. These measures included range and speed of the center of foot pressure. PARTICIPANTS: Eight older, community-dwelling subjects and nine young subjects participated. A sensorimotor evaluation was used to insure that all older individuals were free from any pathologies affecting postural stability. All participants had a low score (indicating high balance confidence) on the Falls Efficacy Scale and no history of falls. RESULTS: Older individuals were affected by modification of the stable visual anchor induced by the opening of doors similar to that of an elevator cage. They showed greater ranges of the center of foot pressure (COP) and speed of the COP after than before the opening of the doors. Furthermore, the increased ranges and speed were two to three times greater than that observed for the young subjects. A lighting intensity considered as comfortable for reading inside the elevator affected the overall postural stability of the older participants negatively. Counting backwards also decreased their overall stability. CONCLUSION: Changing the stable visual anchor, as when exiting an elevator cage, could be a significant risk factor for older persons. Moreover, when combined with a cognitive From the 'Facult6 de mcdecine, UnivcrsitC Laval, Qukbcc, Canada, and tUnivcr-sit6 Joseph Fourier, Grcnoblc, France. Supported by grants from the Natural Science and Engineering Research Council (NSERC) of Canada and Formation dc Chercheur et Aide la Recherche (FCAR) of Qu6bec. M. Simoneau is supported by a scholarship from La Fondation de I'UniversitC Laval.. Addrcss correspondence to Normand Teasdale, UniversitC Laval, Faculti. dc m6dccine, DCpartement de mtdecine sociale et prCvcntive, Division dc kin6siologie, PEPS, QuCbec, QuCbcc, Canada, GIK 7P4. load or lower lighting intensity inside the elevator cage, the negative effects on the postural stability of older persons are exacerbated.
Australasian physical & engineering sciences in medicine, 2017
Postural balance requires using joint strategies which may be changed from normal conditions by interfering with the sensory information. The goal of the present study was to quantitatively evaluate the role of the joint mechanisms during perturbed stance. Visual and cognitive interference was imposed to sixteen healthy young males under rotational toes-down or up perturbations. Power spectral analysis was employed to distinguish the joint contribution and their in- or out-phase co-works. Results showed that addition of cognitive loads reduce the stability by increasing the center of mass (CoM) power to three times greater. Besides the CoM, the knee and hip powers were also significantly enhanced by the cognitive loads (p < .004), but the ankle was not influenced by cognition involvement (p > .05). Elimination of the vision had lower effect on the time and spectral functions of the knee and hip while the ankle rotations were increased due to the lack of visual feedback (p = .0...
International Journal of Building Pathology and Adaptation, 2017
Purpose – Repetitive lifting tasks have detrimental effects upon balance control and may contribute toward fall injuries, yet despite this causal linkage, risk factors involved remain elusive. The purpose of this paper is to evaluate the effects of different weights and lifting postures on balance control using simulated repetitive lifting tasks. Design/methodology/approach – In total, 20 healthy male participants underwent balance control assessments before and immediately after a fatiguing repetitive lifting tasks using three different weights in a stoop (ten participants) or a squat (ten participants) lifting posture. Balance control assessments required participants to stand still on a force plate with or without a foam (which simulated an unstable surface) while center of pressure (CoP) displacement parameters on the force plate was measured. Findings – Results reveal that: increased weight (but not lifting posture) significantly increases CoP parameters; stoop and squat lifting postures performed until subjective fatigue induce a similar increase in CoP parameters; and fatigue adversely effected the participant’s balance control on an unstable surface vis-à-vis a stable surface. Findings suggest that repetitive lifting of heavier weights would significantly jeopardize individuals’ balance control on unstable supporting surfaces, which may heighten the risk of falls. Originality/value – This research offers an entirely new and novel approach to measuring the impact that different lifting weights and postures may have upon worker stability and consequential fall incidents that may arise.
Not just standing there: The use of postural coordination to aid visual tasks
Human Movement Science, 2004
Postural control is an integral part of all physical behavior. Recent research has indicated that postural control functions in a manner that facilitates other higher order (suprapostural) tasks. These studies, while showing that postural sway is modulated in a task specific manner, have not examined the form of postural coordination that allows for the achievement of these higher behavioral goals. The current study examined the relation between visual task constraints (viewing distance), environmental constraints (changes in the surface of support), and the postural coordination employed to complete the task. Thirty-one participants were asked to perform a reading task while standing on various surfaces. Postural motion was recorded from the head, cervico-thoracic spine, sacrum (hip), and ankle. It was found that body segment coordination changed as a function of surface characteristics and task constraints. Additionally, the overall pattern of postural sway (head motion) replicated that which was found by Stoffregen et al. [J. Exp. Psychol. Human Percep. Perform. 25 (6) (1999) 1641. These findings suggest that postural adaptation involves more than basic reduction or increase of motion; it involves the functional coordination of body segments to achieve a particular goal. The data further suggest that there is a need to examine postural control in the absence of external perturbations.