Equilibrium Chair ~ 1960 US Air Force; from “Bioastronautics Research”
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Originally a public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
Wikipedia license: https://creativecommons.org/licenses/by-sa/3.0/
Balance in biomechanics, is an ability to maintain the line of gravity (vertical line from centre of mass) of a body within the base of support with minimal postural sway. Sway is the horizontal movement of the centre of gravity even when a person is standing still. A certain amount of sway is essential and inevitable due to small perturbations within the body (e.g., breathing, shifting body weight from one foot to the other or from forefoot to rearfoot) or from external triggers (e.g., visual distortions, floor translations). An increase in sway is not necessarily an indicator of dysfunctional balance so much as it is an indicator of decreased sensorimotor control…
Maintaining balance requires coordination of input from multiple sensory systems including the vestibular, somatosensory, and visual systems.
Vestibular system: sense organs that regulate equilibrium (equilibrioception); directional information as it relates to head position (internal gravitational, linear, and angular acceleration)
Somatosensory system: senses of proprioception and kinesthesia of joints; information from skin and joints (pressure and vibratory senses); spatial position and movement relative to the support surface; movement and position of different body parts relative to each other
Visual system: Reference to verticality of body and head motion; spatial location relative to objects
The senses must detect changes of spatial orientation with respect to the base of support, regardless of whether the body moves or the base is altered…
Voluntary control of balance
While balance is mostly an automatic process, voluntary control is common. Active control usually takes place when a person is in a situation where balance is compromised. This can have the counter-intuitive effect of increasing postural sway during basic activities such as standing. One explanation for this effect is that conscious control results in over-correcting an instability and “may inadvertently disrupt relatively automatic control processes.” While concentration on an external task “promotes the utilization of more automatic control processes.”
Balance and dual-tasking
Supra-postural tasks are those activities that rely on postural control while completing another behavioral goal, such as walking or creating a text message while standing upright. Research has demonstrated that postural stability operates to permit the achievement of other activities… Research has shown that spontaneous reductions in postural sway occur in response to the addition of a secondary goal.
McNevin and Wulf (2002) found an increase in postural performance when directing an individual’s attention externally compared to directing attention internally That is, focusing attention on the effects of one’s movements rather than on the movement itself will boost performance. This results from the use of more automatic and reflexive control processes. When one is focused on their movements (internal focus), they may inadvertently interfere with these automatic processes, decreasing their performance. Externally focusing attention improves postural stability, despite increasing postural sway at times. It is believed that utilizing automatic control processes by focusing attention externally enhances both performance and learning. Adopting an external focus of attention subsequently improves the performance of supra-postural tasks, while increasing postural stability…