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Physical Hazards of Space Exploration and the Biological Bases of Behavioral Health and Performance in Extreme Environments
Published in Lauren Blackwell Landon, Kelley J. Slack, Eduardo Salas, Psychology and Human Performance in Space Programs, 2020
Julia M. Schorn, Peter G. Roma
Despite the multitude of spaceflight analogues, microgravity is the only spaceflight stressor that cannot be consistently simulated on Earth. Although commonly referred to as “zero-g,” this term is misleading, as a small amount of gravity exists in space. Microgravity affects the body in a multitude of ways. When gravity is not acting on fluids in the body, blood and cerebrospinal fluid shift to the head, resulting in a “puffy” face and thin legs. This fluid shift also enables space motion sickness, headaches, and visual impairments. As pressure builds from the increase of blood flow to the brain, vision can become distorted, part of a phenomenon termed Spaceflight Associate Neuro-ocular Syndrome (SANS; Lee, Mader, Gibson, & Tarver, 2017; Marshall-Goebel, Damani, & Bershad, 2019). Dizziness and motor coordination are also affected by microgravity, especially seen when astronauts return to the Earth and can barely stand or walk in a straight line. The vestibular system in the inner ear relies on gravity to sense direction and maintain balance. Astronauts typically take a couple of weeks to adjust to microgravity in space and to gravity back on Earth. During this transition, astronauts may experience nausea and deterioration in spatial orientation, hand–eye coordination, balance, and locomotion (Bloomberg, Reschke, Clement, Mulavara, & Taylor, 2015).
Audition and Vestibular Function
Published in Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell, Introduction to Human Factors, 2017
Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell
Several other structures are located in the inner ear, including three semicircular canals (anterior, posterior, and horizontal) (see Figure 4.3) and otolith organs that comprise the vestibular system. The vestibular system provides information about the orientation of the body in space and about the orientation and motion of the head and body. The three semicircular canals are oriented at right angles to one another and encode rotation of the head along any of three axes X, Y, and Z. Acceleration is detected by hair cells called stereocilia found in each semicircular canal, which, like the cochlea, contains fluid that is displaced by sudden movements. The displacement of the fluid in the canal bends the hair cells whose response encodes information concerning the direction and rate of rotation of the head.
Biomechanical studies for understanding falls in older adults
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
Daina L. Sturnieks, R. Stephen
The vestibular system involves inner ear structures that detect position and motion of the head, relative to gravity, and is important for posture and coordination of head, eye and body movements. Recent studies have reported significant associations between vestibular impairment and fall-related fractures. Kristinsdottir and colleagues have used a head-shaking stimulus applied when subjects were in a supine position to induce nystagmus — a sign indicating asymmetry of the vestibular reflexes. In an initial study comprising 19 subjects (mean age 72 years) with hip fracture and 28 aged-matched controls, they found that 68 per cent of the hip fracture subjects demonstrated a nystagmus following the head-shake stimulus compared with 32 per cent of the controls (Kristinsdottir et al., 2000). Similar findings were reported in a subsequent study of older wrist fracture patients (Kristinsdottir et al., 2001). Vestibular function is less amenable to assessment with simple screening tests compared with vision and peripheral sensation. However, these recent studies provide preliminary evidence that when assessed with greater precision, impaired vestibular function may be an important risk factor for falls and fall-related fractures in older people.
RESNA position on the application of dynamic seating
Published in Assistive Technology, 2021
Michelle L. Lange, Barbara Crane, Frederick J. Diamond, Suzanne Eason, Jessica Presperin Pedersen, Greg Peek
From a sensory standpoint, movement provides vestibular input. The vestibular system is responsible for processing movement, changes in head position, and direction and speed of movement. The vestibular system lies in the inner ear. When the vestibular system is activated, the brain can be either calmed or aroused (B. Pfeiffer et al., 2008). An agitated client may become calm (decreased agitation) when the vestibular system is activated; a sub-aroused client may become more alert. Maladaptive behaviors may be reduced in response to movement (B. A. Pfeiffer et al., 2011). Dynamic seating has been shown to increase attention. Rollo et al. (2017) reviewed 5 studies and found that classroom based dynamic seating improved attention. One study showed that clients with dementia who were agitated, calmed in response to rocking. Other clients with dementia who were sub-aroused became more alert and responsive after rocking, specifically with reduced depression and anxiety (Watson et al., 1998). Dynamic seating can increase sensory input (Presperin Pedersen & Eason, 2015 [clinician consensus]).
The role of subconcussive impacts on sway velocities in Division I men’s lacrosse players
Published in Sports Biomechanics, 2020
Theresa L. Miyashita, Eleni Diakogeorgiou, Kaitlyn Marrie
Vestibular system dysfunction is associated with impaired postural control and balance deficits (Guskiewicz, 2011). Impairment to the vestibular system following a concussion, is linked to a delayed recovery (Hoffer, Gottshall, Moore, Balough, & Wester, 2004; Lau, Kontos, Collins, Mucha, & Lovell, 2011; Naguib et al., 2012). As approximately 50% of concussion cases are associated with vestibular system dysfunction (Kontos et al., 2012), there is cause for concern regarding prompt and successful recovery. The brain’s inability to orient itself following concussion may be due to the disruption of hair cells or dislodging otoliths (Mucha, Collins, & French, 2012). Theoretically, repetitive hits to the head would have the same effect on the hair cells and otoliths, resulting in balance disturbances in otherwise healthy individuals. Centre of pressure measures, specifically sway, is a common method to quantify standing balance, and sway velocity is considered a reliable means of assessing balance (Lin, Seol, Nussbaum, & Madigan, 2008). Sway velocity is a neuromuscular response, with lower scores equating to an improved ability in maintaining balance within limits of stability (McGuine, Greene, Best, & Leverson, 2000).
Comparison of control strategies for the cervical muscles of an average female head-neck finite element model
Published in Traffic Injury Prevention, 2019
I Putu A. Putra, Johan Iraeus, Robert Thomson, Mats Y. Svensson, Astrid Linder, Fusako Sato
Muscle control depends on voluntary motion task, feedback through the body’s internal and external sensory systems, and reflexive motions. In this study, two main sensory feedback systems have been identified as relevant for modeling muscle response in a rear impact. The vestibular system and muscle spindles give feedback to the CNS for stabilizing the human head-neck complex (Keshner 2009). The sensory information from the vestibular system is used to balance the head and body in space by sensing the rotational and translational motion of head (Keshner 2009). Muscle spindles, which are found in high concentrations in the deep neck muscles (Keshner 2009), provide information to the CNS for the head-on-trunk orientation by sensing muscle length and the changes in the muscle length (Keshner 2009). Both these systems are relevant for the loading condition in a rear impact where the torso is disturbed and the resulting head and neck motions are assumed to be minimized by reflexive mechanisms steered by these two systems.