Neurovestibular effects of bed rest and centrifugation

Jarchow, Thomas; Young, Laurence R.

doi:10.3233/ves-2010-0350

Cited by 10 publications

(4 citation statements)

References 5 publications

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“…Similar adaptations of physiological systems during spaceflight have also been observed during and after HDBR 22 – 26 . In addition, prolonged HDBR has been shown to have adverse effects on both the vestibular system 27 , 28 and postural stability 29 . With limited resources for human research during spaceflight, prolonged HDBR provides an ideal experimental setting to study post-flight deconditioning in astronauts.…”

Section: Introductionmentioning

confidence: 99%

Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization

Tremblay

Verma

et al. 2020

Sci Rep

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To understand fundamental mechanisms associated with post-flight orthostatic intolerance we investigated the interaction between the cardiovascular and postural functions before and after 60 days of head down bedrest (HDBR). Twenty healthy young males (35.0 ± 1.7 years) were subjected to 60-day HDBR at 6˚ to simulate spaceflight-induced fluid shifts. A supine-to-stand (STS) test was conducted to evaluate cardio-postural control before and after (R) HDBR while an assessment of cardiovascular function was performed during HDBR. Beat-to-beat heart period, systolic blood pressure, and electromyography impulses were derived for wavelet transform coherence and causality analyses of the cardio-postural control and used to assess changes in the muscle-pump baroreflex. During quiet stand of the STS test, compared to baseline, heart rate was 50% higher on the day of exit from bedrest (R0) and 20% higher eight days later (R8). There was a 50% increase in deoxygenated hemoglobin on R0 and R8. Leg muscle activity reduced, and postural sway increased after HDBR. Causality of the muscle-pump baroreflex was reduced on R0 (0.73 ± 0.2) compared to baseline (0.87 ± 0.2) with complete recovery by R8. The muscle-pump baroreflex also had decreased gain and fraction time active following HDBR. Overall, our data show a significantly impaired muscle-pump baroreflex following bedrest. Spaceflight-induced weightlessness produces time-dependent physiological adaptation responses 1-3. Once adapted to weightlessness, many responses become inappropriate upon return to a gravitational environment. The resulting physiological deconditioning could pose a serious challenge in the event of a critical post-landing situation requiring rapid escape from a spacecraft. Orthostatic intolerance after spaceflight remains a health and safety concern for astronauts, not just on landing day but also in the days of recovery 4. Similar physiological deconditioning is seen following long lasting bedrest confinements (e.g. in young persons participating in head down bedrest studies, or in older persons due to chronic diseases or after falls and falls-related injuries) 5. Gravitational effects on the cardiovascular system during upright posture (orthostatic loading) induce a decrease in blood pressure which, if not compensated for, will cause loss of consciousness 6. Baroreflex plays an essential role in maintaining blood pressure equilibrium under orthostatic loading. In regards to the arterial baroreflex, two processes exist in tandem: one in which blood pressure alters baroreceptor output and hence heart rate and vasomotor tone 7-9 ; and, a second in which changes in heart rate and vasomotor tone alters blood pressure-the former a baroreflex (feed-back) and the latter a non-baroreflex (feed-forward) control of blood pressure 10. Similarly, conscious movement could place a person in a position of instability, which would require post-movement adjustment to maintain an upright stance. Therefore, any change in body position (feed-forward) must be accompanied with ...

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Section: Introductionmentioning

confidence: 99%

Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization

Tremblay

Verma

et al. 2020

Sci Rep

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“…5B) suggesting that the weighting of gravity relative to the body was not significantly altered by HDBR and thus suggesting that the weighting of the body and gravity cues both increased relative to vision. An increase in the weighting of the body might underlie the observation that after 21 days of HDBR participants feel that they are lying horizontal rather than 6 • head down [27].…”

Section: Cue Weightingsmentioning

confidence: 99%

“…Not only are many of these perceptual effects debilitating, but they also represent a significant safety hazard when navigating in an emergency, and operational issues when working with oriented switches and devices. Only a few studies have attempted to look at whether HDBR induces comparable perceptual effects and they have generally had disappointing results [27,39]. Here we investigate the effects of HDBR on the perception of self-orientation using a method that has proven successful in long duration spaceflight.…”

Section: Introductionmentioning

confidence: 99%

Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright

Harris

Jenkin

Herpers

2022

VES

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BACKGROUND: Humans demonstrate many physiological changes in microgravity for which long-duration head down bed rest (HDBR) is a reliable analog. However, information on how HDBR affects sensory processing is lacking. OBJECTIVE: We previously showed (25) that microgravity alters the weighting applied to visual cues in determining the perceptual upright (PU), an effect that lasts long after return. Does long-duration HDBR have comparable effects? METHODS: We assessed static spatial orientation using the luminous line test (subjective visual vertical, SVV) and the oriented character recognition test (PU) before, during and after 21 days of 6° HDBR in 10 participants. Methods were essentially identical as previously used in orbit (25). RESULTS: Overall, HDBR had no effect on the reliance on visual relative to body cues in determining the PU. However, when considering the three critical time points (pre-bed rest, end of bed rest, and 14 days post-bed rest) there was a significant decrease in reliance on visual relative to body cues, as found in microgravity. The ratio had an average time constant of 7.28 days and returned to pre-bed-rest levels within 14 days. The SVV was unaffected. CONCLUSIONS: We conclude that bed rest can be a useful analog for the study of the perception of static self-orientation during long-term exposure to microgravity. More detailed work on the precise time course of our effects is needed in both bed rest and microgravity conditions.

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“…HDBR studies have also investigated the effects of AG by having participants undergo daily centrifugation as a potential countermeasure. A 21-day HDBR investigation reported that participants that received daily AG shifted their position perception to be 30° closer to upright than those that did not 37 . A more recent study found that intermittent (six bouts of five minutes each) AG reduced HDBR-associated orthostatic intolerance following five days of HDBR more than a continuous daily session of 30 minutes 38 .…”

Section: Introdutionmentioning

confidence: 99%

Artificial Gravity During a Spaceflight Analog Alters Brain Sensory Connectivity

McGregor

Lee

Mulder

et al. 2022

Preprint

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Spaceflight has numerous untoward effects on human physiology. Various countermeasures are under investigation including artificial gravity (AG). Here, we investigated whether AG alters resting-state brain functional connectivity changes during head-down tilt bed rest (HDBR), a spaceflight analog. Participants underwent 60 days of HDBR. Two groups received daily AG administered either continuously (cAG) or intermittently (iAG). A control group received no AG. We assessed resting-state functional connectivity before, during, and after HDBR. We also measured balance and mobility changes from pre- to post-HDBR. We examined how functional connectivity changes throughout HDBR and whether AG is associated with differential effects. We found differential connectivity changes by group between posterior parietal cortex and multiple somatosensory regions. The control group exhibited increased functional connectivity between these regions throughout HDBR whereas the cAG group showed decreased functional connectivity. This finding suggests that AG alters somatosensory reweighting during HDBR. We also observed brain-behavioral correlations that differed significantly by group. Control group participants who showed increased connectivity between the putamen and somatosensory cortex exhibited greater mobility declines post-HDBR. For the cAG group, increased connectivity between these regions was associated with little to no mobility declines post-HDBR. This suggests that when somatosensory stimulation is provided via AG, functional connectivity increases between the putamen and somatosensory cortex are compensatory in nature, resulting in reduced mobility declines. Given these findings, AG may be an effective countermeasure for the reduced somatosensory stimulation that occurs in both microgravity and HDBR.

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Neurovestibular effects of bed rest and centrifugation

Cited by 10 publications

References 5 publications

Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization

Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization

Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright

Artificial Gravity During a Spaceflight Analog Alters Brain Sensory Connectivity

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