Postural Reflexes, Balance Control, and Functional Mobility with Long-Duration Head-Down Bed Rest

Head-down tilt bed rest (HDBR) has been used as a spaceflight analog to study some of the effects of microgravity on human physiology, cognition, and sensorimotor functions. Previous studies have reported declines in balance control and functional mobility after spaceflight and HDBR. In this study we investigated how the brain activation for foot movement changed with HDBR. Eighteen healthy men participated in the current HDBR study. They were in a 6° head-down tilt position continuously for 70 days. Functional MRI scans were acquired to estimate brain activation for foot movement before, during, and after HDBR. Another 11 healthy men who did not undergo HDBR participated as control subjects and were scanned at four time points. In the HDBR subjects, the cerebellum, fusiform gyrus, hippocampus, and middle occipital gyrus exhibited HDBR-related increases in activation for foot tapping, whereas no HDBR-associated activation decreases were found. For the control subjects, activation for foot tapping decreased across sessions in a couple of cerebellar regions, whereas no activation increase with session was found. Furthermore, we observed that less HDBR-related decline in functional mobility and balance control was associated with greater pre-to-post HDBR increases in brain activation for foot movement in several cerebral and cerebellar regions. Our results suggest that more neural control is needed for foot movement as a result of HDBR. NEW & NOTEWORTHY Long-duration head-down bed rest serves as a spaceflight analog research environment. We show that brain activity in the cerebellum and visual areas during foot movement increases from pre- to post-bed rest and then shows subsequent recovery. Greater increases were seen for individuals who exhibited less decline in functional mobility and balance control, suggestive of adaptive changes in neural control with long-duration bed rest.

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Perilymph Fistulas

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348947808700606 ◽

1978 ◽

Vol 87 (6) ◽

pp. 797-803 ◽

Cited By ~ 45

Author(s):

George T. Singleton ◽

Kathryn Nolan Post ◽

Marc Simeon Karlan ◽

Douglas G. Bock

Keyword(s):

Discriminant Analysis ◽

Effective Means ◽

Bed Rest ◽

Sudden Onset ◽

Effective Control ◽

Speech Discrimination ◽

Mean Values ◽

Long Duration ◽

History Of ◽

Physical Findings

Fifty-one patients suspected of having a perilymph fistula were evaluated. We postulated that many patients with predominantly vestibular complaints had unrecognized perilymph fistulas. An analysis was made of symptoms, physical findings, vestibular and audiometric test results in order to determine appropriate diagnostic criteria for the presence of perilymph fistulas. The patient population was divided into two groups, those with and without fistulas. Data from both groups were compared by mean values of variables, step-wise discriminant analysis, and factor analysis. A history of trauma with sudden onset of dizziness and/or hearing loss should alert the physician to a fistula. Findings of significance were positional nystagmus of short latency and long duration without import of nystagmus direction, canal paresis and reduced speech reception threshold with poor speech discrimination scores. Discriminant analysis correctly classified 19 fistula and 10 nonfistula cases explored operatively and identified two error judgments in 22 nonoperated cases. Bed rest for the first five days proved to be the most effective means of therapy. Surgical intervention with repair of the fistula by perichondrial graft provided effective control of vertigo more frequently than restoration of hearing.

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Long-term bedrest study and astronaut training

10.7287/peerj.preprints.1834 ◽

2016 ◽

Author(s):

Edwin Mulder ◽

Alexandra Noppe ◽

Ulrich Limper

Keyword(s):

Bed Rest ◽

Dual Purpose ◽

Planetary Environments ◽

Exercise Regimen ◽

Long Duration ◽

Astronaut Training ◽

Health Support ◽

Art Research ◽

Induced Changes

In the context of space physiology, research is being conducted to understand the physiological effects from radiation, hypogravity, spaceflight and planetary environments. The goal is to identify new methods to address the unique challenges in medical treatment, human factors, and behavioral health support on future exploration missions. As crew size is small and time is limited during actual missions, space agencies resort to addressing the effects of space travel in analog environments that have features similar to those of spaceflight. Head-down tilt bed rest (HDBR), for instance, is one of the established terrestrial models used to simulate some of the physiological changes experienced during spaceflight under weightless conditions and is therefore considered a valuable testbed to prepare for future long-duration exploration missions. HDBR studies are performed in extremely-well controlled laboratory settings, offering the possibility to test the effects of – what is in essence - physical inactivity and fluid shift. However, HDBR studies have a dual purpose, as they are also invaluable for the development, testing and validation of countermeasures aimed at mitigating microgravity-induced changes to the human body. With respect to the latter, the consensus is that short-term bed rest studies (< 14 days) serve foremost as a first screening of potential promising countermeasures, particularly for the cardiovascular system. Screening of preventative procedures and protocols for the muscular system requires at least mid-term (14 -28 days), whereas studies aiming to validate countermeasures for bone require long-term HDBR studies, in the order of 60-90 days. Hitherto the preferred countermeasure during spaceflight has been physical exercise. The presentation will therefore provide a short overview of the current onboard exercise regimen and will, in light of this, outline the scientific background and aims of the ongoing 60-day HDBR study at the :envihab (from the words ‘Environment’ and ‘Habitat’), the DLR Institute of Aerospace Medicine’s state-of-the-art research facility.

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Decreased otolith-mediated vestibular response in 25 astronauts induced by long-duration spaceflight

Journal of Neurophysiology ◽

10.1152/jn.00065.2016 ◽

2016 ◽

Vol 115 (6) ◽

pp. 3045-3051 ◽

Cited By ~ 23

Author(s):

Emma Hallgren ◽

Ludmila Kornilova ◽

Erik Fransen ◽

Dmitrii Glukhikh ◽

Steven T. Moore ◽

...

Keyword(s):

Orthostatic Intolerance ◽

Balance Control ◽

Head Tilt ◽

Otolith Organs ◽

Negative Effects ◽

Spatial Disorientation ◽

Long Duration ◽

Before And After ◽

Ocular Counterrolling ◽

Otolith System

The information coming from the vestibular otolith organs is important for the brain when reflexively making appropriate visual and spinal corrections to maintain balance. Symptoms related to failed balance control and navigation are commonly observed in astronauts returning from space. To investigate the effect of microgravity exposure on the otoliths, we studied the otolith-mediated responses elicited by centrifugation in a group of 25 astronauts before and after 6 mo of spaceflight. Ocular counterrolling (OCR) is an otolith-driven reflex that is sensitive to head tilt with regard to gravity and tilts of the gravito-inertial acceleration vector during centrifugation. When comparing pre- and postflight OCR, we found a statistically significant decrease of the OCR response upon return. Nine days after return, the OCR was back at preflight level, indicating a full recovery. Our large study sample allows for more general physiological conclusions about the effect of prolonged microgravity on the otolith system. A deconditioned otolith system is thought to be the cause of several of the negative effects seen in returning astronauts, such as spatial disorientation and orthostatic intolerance. This knowledge should be taken into account for future long-term space missions.

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Towards Using the Instrumented Timed Up-and-Go Test for Screening of Sensory System Performance for Balance Control in Older Adults

Sensors ◽

10.3390/s19030622 ◽

2019 ◽

Vol 19 (3) ◽

pp. 622 ◽

Cited By ~ 3

Author(s):

Thomas Gerhardy ◽

Katharina Gordt ◽

Carl-Philipp Jansen ◽

Michael Schwenk

Keyword(s):

Older Adults ◽

System Performance ◽

Fall Risk ◽

Balance Control ◽

Sensory System ◽

Sensory Systems ◽

Community Dwelling ◽

Functional Mobility ◽

Timed Up And Go ◽

Community Dwelling Older Adults

Background: Decreasing performance of the sensory systems’ for balance control, including the visual, somatosensory and vestibular system, is associated with increased fall risk in older adults. A smartphone-based version of the Timed Up-and-Go (mTUG) may allow screening sensory balance impairments through mTUG subphases. The association between mTUG subphases and sensory system performance is examined. Methods: Functional mobility of forty-one community-dwelling older adults (>55 years) was measured using a validated mTUG. Duration of mTUG and its subphases ‘sit-to-walk’, ‘walking’, ‘turning’, ‘turn-to-sit’ and ‘sit-down’ were extracted. Sensory systems’ performance was quantified by validated posturography during standing (30 s) under different conditions. Visual, somatosensory and vestibular control ratios (CR) were calculated from posturography and correlated with mTUG subphases. Results: Vestibular CR correlated with mTUG total time (r = 0.54; p < 0.01), subphases ‘walking’ (r = 0.56; p < 0.01), and ‘turning’ (r = 0.43; p = 0.01). Somatosensory CR correlated with mTUG total time (r = 0.52; p = 0.01), subphases ‘walking’ (r = 0.52; p < 0.01) and ‘turning’ (r = 0.44; p < 0.01). Conclusions: Supporting the proposed approach, results indicate an association between specific mTUG subphases and sensory system performance. mTUG subphases ‘walking’ and ‘turning’ may allow screening for sensory system deterioration. This is a first step towards an objective, detailed and expeditious balance control assessment, however needing validation in a larger study.

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Head-down tilt bed rest with or without artificial gravity is not associated with motor unit remodeling

European Journal of Applied Physiology ◽

10.1007/s00421-020-04458-7 ◽

2020 ◽

Vol 120 (11) ◽

pp. 2407-2415 ◽

Cited By ~ 1

Author(s):

Julia Attias ◽

Andrea Grassi ◽

Alessandra Bosutti ◽

Bergita Ganse ◽

Hans Degens ◽

...

Keyword(s):

Motor Unit ◽

Compound Muscle Action Potential ◽

Bed Rest ◽

Artificial Gravity ◽

Whole Body ◽

Healthy Individuals ◽

Long Duration ◽

Muscle Action Potential ◽

Abductor Digiti Minimi ◽

Healthy Participants

Abstract Purpose The objective of this study was to assess whether artificial gravity attenuates any long-duration head-down 60 bed rest (HDBR)-induced alterations in motor unit (MU) properties. Methods Twenty-four healthy participants (16 men; 8 women; 26–54 years) underwent 60-day HDBR with (n = 16) or without (n = 8) 30 min artificial gravity daily induced by whole-body centrifugation. Compound muscle action potential (CMAP), MU number (MUNIX) and MU size (MUSIX) were estimated using the method of Motor Unit Number Index in the Abductor digiti minimi and tibialis anterior muscles 5 days before (BDC-5), and during day 4 (HDT4) and 59 (HDT59) of HDBR. Results The CMAP, MUNIX, and MUSIX at baseline did not change significantly in either muscle, irrespective of the intervention (p > 0.05). Across groups, there were no significant differences in any variable during HDBR, compared to BDC-5. Conclusion Sixty days of HDBR with or without artificial gravity does not induce alterations in motor unit number and size in the ADM or TA muscles in healthy individuals.

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LBNP exercise protects aerobic capacity and sprint speed of female twins during 30 days of bed rest

Journal of Applied Physiology ◽

10.1152/japplphysiol.91502.2008 ◽

2009 ◽

Vol 106 (3) ◽

pp. 919-928 ◽

Cited By ~ 25

Author(s):

Stuart M. C. Lee ◽

Suzanne M. Schneider ◽

Wanda L. Boda ◽

Donald E. Watenpaugh ◽

Brandon R. Macias ◽

...

Keyword(s):

Treadmill Exercise ◽

Lower Body Negative Pressure ◽

Bed Rest ◽

Exercise Group ◽

Peak Oxygen Consumption ◽

Control Group ◽

Treadmill Test ◽

Sprint Speed ◽

Long Duration ◽

Volitional Fatigue

We have shown previously that treadmill exercise within lower body negative pressure (LBNPex) maintains upright exercise capacity (peak oxygen consumption, V̇o2peak) in men after 5, 15, and 30 days of bed rest (BR). We hypothesized that LBNPex protects treadmill V̇o2peak and sprint speed in women during a 30-day BR. Seven sets of female monozygous twins volunteered to participate. Within each twin set, one was randomly assigned to a control group (Con) and performed no countermeasures, and the other was assigned to an exercise group (Ex) and performed a 40-min interval (40–80% pre-BR V̇o2peak) LBNPex (51 ± 5 mmHg) protocol, plus 5 min of static LBNP, 6 days per week. Before and immediately after BR, subjects completed a 30.5-m sprint test and an upright graded treadmill test to volitional fatigue. These results in women were compared with previously reported reductions in V̇o2peak and sprint speed in male twins after BR. In women, sprint speed (−8 ± 2%) and V̇o2peak (−6 ± 2%) were not different after BR in the Ex group. In contrast, both sprint speed (−24 ± 5%) and V̇o2peak (−16 ± 3%) were significantly less after BR in the Con group. The effect of BR on sprint speed and V̇o2peak after BR was not different between women and men. We conclude that treadmill exercise within LBNP protects against BR-induced reductions in V̇o2peak and sprint speed in women and should prove effective during long-duration spaceflight.

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